Glossary

18650 Cell

A cylindrical rechargeable lithium-ion cell, named for its size of about 18 mm across and 65 mm long. Many are made as component parts for battery packs. The CPSC warns consumers not to use loose 18650 cells separated from battery packs, because they can lack protection circuits and can short-circuit, overheat, and catch fire.

Related: Lithium Iron Phosphate (LiFePO4)

811 (Call Before You Dig)

The national call-before-you-dig number. One free call brings every buried utility near a project located and marked within a few working days, and calling before excavation is the law in every state.

Related: National Pipeline Mapping System (NPMS)

911 System

The national emergency telephone number that connects callers to local police, fire, and EMS dispatch. The 911 system depends on telecommunications infrastructure (cell towers, telephone switches, and dispatch center equipment), all of which can fail during major disasters. During the 2021 Texas grid collapse, some 911 centers lost power and reverted to backup systems with reduced capacity.

Related: Emergency Alert System (EAS), Wireless Emergency Alert (WEA)

72-Hour Bag

A pre-packed bag containing essential supplies for at least 72 hours, ready to grab during an evacuation. It typically includes water, food, medications, documents, a flashlight, a battery-powered radio, cash, and a change of clothes. Evacuation decisions happen fast, and having a bag ready eliminates the scramble to gather supplies under stress.

Related: Evacuation Order

Access and Functional Needs (AFN)

The emergency-management term for people who may need extra help to prepare for, respond to, or recover from a disaster. FEMA's list includes older adults, people with disabilities, people with limited English, and people with limited access to transportation or money.

Related: Federal Emergency Management Agency (FEMA)

Actual Cash Value (ACV)

What a damaged or stolen item was worth at the time of the loss: the cost to replace it, minus depreciation for age and wear. A policy that pays actual cash value pays what the used item was worth, not what a new one costs.

Related: Replacement Cost, Deductible

Additional Living Expenses (ALE)

A component of renter's or homeowner's insurance that covers the cost of temporary housing, meals, and other necessary expenses when your home is uninhabitable due to a covered peril such as fire, water damage, or storm damage. ALE pays the difference between your normal living costs and the increased costs of living elsewhere.

Related: Renter's Insurance, Insurance Adjuster

Advance Directive

A legal document that tells health care providers what care a person does or does not want if they cannot speak for themselves. The two common forms are a living will, which states wishes about treatments such as CPR or a breathing machine, and a health care power of attorney, which names someone to decide.

Related: Health Care Power of Attorney, Do-Not-Resuscitate (DNR) Order

After-Action Report (AAR)

A structured review document produced after a disaster or emergency exercise that evaluates what happened, what worked, what failed, and what should change. AARs are the primary mechanism by which emergency management learns from events. They are the most reliable source for understanding disaster response decisions and outcomes.

Related: Incident Command System (ICS), Federal Emergency Management Agency (FEMA), Emergency Operations Center (EOC)

Agency

The power and confidence to act on your own decisions rather than waiting for instructions or rescue. Agency is the central outcome of all preparedness work: a person with a plan, supplies, skills, and practiced routines does not need to be told what to do when conditions change. Building agency is the reason NWS exists.

Related: Autonomy, Capability, Fortitude

Air Installations Compatible Use Zones (AICUZ)

The published study in which a military air station maps its aircraft noise contours and the accident potential zones off its runway ends. Local governments use it for land-use planning, and it is worth reading before buying a home near an air station.

Amazon Sidewalk

A shared, low-bandwidth wireless network that Amazon runs through compatible Echo and Ring devices in people's homes. It lets some Ring lights and sensors stay connected beyond the reach of home Wi-Fi without a separate hub. It is optional, can be turned off in the Alexa app, and Amazon caps its data use at 500 MB per month per account.

America Eats (WPA)

An unfinished WPA Federal Writers' Project initiative (late 1930s–1941) that set out to document American food traditions region by region. Writers across the country produced essays on local foodways, community meals, ethnic food traditions, and seasonal customs before the project was abandoned when the U.S. entered World War II. Over 200,000 pages of manuscript survive and are a primary source for regional foodways research.

Related: Works Progress Administration (WPA), Federal Writers' Project

Anemometer

An instrument that measures wind speed, mounted on a mast at or near the height a turbine would occupy. Site screening depends on measured wind rather than mapped wind, because regional maps cannot see the obstructions on a particular property.

Related: Wind Shear, Turbulence, Cut-In Wind Speed

Annual Increment

The volume of new wood a stand of trees adds in one year, usually expressed in cords or cubic feet per acre. It sets the ceiling on how much firewood a woodlot can supply indefinitely, because cutting more than the annual increment draws down the standing stock rather than living off the growth.

Related: Cord (of firewood)

ANSI (American National Standards Institute)

The private non-profit body that accredits standards developers in the United States and approves the results as American National Standards. ANSI does not usually write standards itself. Organizations such as ASME and NSF develop them, and ANSI approval signals that the drafting process was open and balanced. A standard described as ANSI approved has met that procedural bar, which is a statement about how the document was written rather than a certification of any particular product.

Related: NSF/ANSI Certification

ANSI/BHMA Lock Grade

A strength and durability rating for door locks, set by the Builders Hardware Manufacturers Association and published as American National Standards. Grade 1 is the highest, Grade 2 is common in homes, and Grade 3 is the minimum. Deadbolts are rated under the A156.5 standard, which tests repeated use and resistance to forced entry.

Related: Strike Plate, Solid-Core Door

Amateur Radio Emergency Service (ARES)

A volunteer program organized by the ARRL in which licensed amateur radio operators provide emergency communications during disasters. ARES groups coordinate with local emergency management agencies and activate when normal communications are disrupted. Membership requires only an amateur radio license and willingness to train.

Related: Amateur (Ham) Radio, American Radio Relay League (ARRL), Community Emergency Response Team (CERT)

American Radio Relay League (ARRL)

The national membership organization for amateur radio operators in the United States, founded in 1914. ARRL provides licensing exam resources, emergency communication training, and a nationwide network of local radio clubs. The ARRL section finder is the fastest way to locate a ham radio club in your area.

Related: Amateur (Ham) Radio, Amateur Radio Emergency Service (ARES), Community Emergency Response Team (CERT)

American Society of Civil Engineers (ASCE)

The professional organization for civil engineers in the United States, which publishes the Infrastructure Report Card, a quadrennial assessment grading the condition of U.S. infrastructure across 17 categories. ASCE grades are widely cited in policy discussions and provide the most thorough public assessment of infrastructure condition. The most recent report card gave U.S. infrastructure an overall grade of C-minus.

Related: Design Basis, Building Code, Levee, Water Main

ASME B107

The family of American National Standards covering hand tools and accessories, published by ASME after approval by ASME and ANSI. The committee scope sets performance and safety requirements for wrenches, pliers and snips, screwdrivers, striking and struck tools, and torque instruments, along with the tests that determine whether a tool conforms. Safety considerations were added to the scope in 1996. It is not a consumer certification program, so there is no mark to look for on retail packaging and no public database of certified household tools to search.

Related: ANSI (American National Standards Institute), Chrome Vanadium (Cr-V)

Aunt Sammy

The fictional persona, Uncle Sam's wife, who hosted the USDA's 'Housekeepers' Chats' radio program from 1926 to 1946. Local actresses read USDA-supplied scripts featuring practical cooking advice, household tips, and economical recipes to millions of listeners. The compiled recipe books from the program are among the most widely distributed government publications of the 20th century.

Related: Bureau of Home Economics, Hazel Stiebeling

Autonomy

The ability to operate independently and make decisions without relying on external systems or approval. In preparedness, autonomy means a household can sustain itself when supply chains, utilities, or services are interrupted. Autonomy is not isolation; it is the capacity to function on your own terms when needed.

Related: Independence, Self-Sufficiency, Agency

Amateur (Ham) Radio

A licensed radio communication system that operates independently of cell towers, internet, and commercial infrastructure. During disasters that knock out normal communications, ham radio operators provide emergency message relay, damage reports, and coordination support. Earning a Technician-class license requires passing a 35-question FCC exam. No Morse code is required.

Related: American Radio Relay League (ARRL), Community Emergency Response Team (CERT), SKYWARN, Amateur Radio Emergency Service (ARES)

American Red Cross

The nonprofit humanitarian organization that provides emergency shelter, food, and health services during and after disasters in the United States. Red Cross volunteers staff shelters, distribute supplies, and provide mental health support. The organization also offers first aid, CPR, and water safety training courses that are widely recognized as baseline certifications.

Related: Community Emergency Response Team (CERT), First Aid

Avian Influenza (Bird Flu)

A contagious viral disease of wild and domestic birds, caused by influenza type A viruses. Highly pathogenic strains (HPAI) can kill whole poultry flocks quickly, while wild birds can carry the virus without appearing sick. In the United States, owners report sick or dying birds to their state veterinarian or to USDA at 1-866-536-7593.

Related: Biosecurity, National Poultry Improvement Plan (NPIP)

Backflow Preventer

A plumbing device that allows water to flow in one direction only, preventing contaminated water from flowing backward into the clean supply. Building codes require backflow prevention on any connection between a potable water line and a non-potable source, including inline water storage systems.

Related: Distribution System, Potable Water

Backflush

A filter maintenance technique that reverses the direction of water flow through a filter element to clear trapped particles and restore flow rate. For hollow fiber membrane filters like the Sawyer Squeeze, backflushing uses clean water pushed through the output end of the filter to dislodge debris caught in the pores. Regular backflushing extends filter life and maintains filtration performance.

Related: Hollow Fiber Membrane, Micron

Bare-Bones Budget

A stripped-down spending plan that covers only essential expenses, such as housing, utilities, food, insurance, and minimum debt payments. Households use it when income drops, so they know in advance how little they can live on and which spending can pause.

Betz Limit (Betz's Law)

The theoretical ceiling on how much energy a wind turbine can extract from the air passing through its rotor. It follows from the physics of a slowing airstream rather than from any engineering shortcoming, so no blade design can exceed it. Betz's law caps extraction at 59.3 percent of the energy in the airstream.

Related: Rotor Diameter, Capacity Factor, Power Curve

Biofilter

The part of an aquarium or aquaponic system where nitrifying microbes live, on wet surfaces such as grow-bed media, filter media, and tank walls. A working biofilter keeps ammonia and nitrite low enough for fish. Harsh cleaning, chlorinated water, or low oxygen can set it back.

Related: Nitrification, Chloramine

Biosecurity

The routine practices that keep disease out of a flock or herd and stop it from spreading if it arrives. They include limiting visitors, keeping clothing, shoes, hands, and equipment clean, and keeping wild birds and other wildlife away from animals, feed, and water. USDA's Defend the Flock program teaches these steps to backyard and commercial poultry owners.

Related: Avian Influenza (Bird Flu), National Poultry Improvement Plan (NPIP)

Bit Driver

A handle that accepts interchangeable screwdriver tips, called bits, rather than carrying one fixed tip. A bit driver and a bit set replace a drawer of individual screwdrivers and take up far less room in a tool case. The trade is a small amount of play at the joint between bit and handle, which matters on a seized fastener and rarely on ordinary household work.

Related: Cam-Out

Block Captain

A volunteer who serves as the primary point of contact for emergency communication and coordination on a single block or small neighborhood area. Block captains maintain the communication tree, keep the neighborhood contact sheet current, and serve as the liaison to local emergency management during events. The role requires no formal training, just willingness to organize and a current contact list.

Related: Communication Tree, Map Your Neighborhood (MYN), Community Emergency Response Team (CERT)

Boil Water Advisory

A public health notice issued when a water system may have been contaminated, typically after a main break, treatment plant failure, or natural disaster. The advisory means tap water should be brought to a rolling boil for at least one minute before drinking, cooking, or brushing teeth. Boil advisories are issued by local water utilities or health departments and remain in effect until testing confirms the water is safe.

Related: Water Main

Botulism

A rare but severe form of food poisoning caused by a toxin produced by the bacterium Clostridium botulinum, which thrives in low-oxygen, low-acid environments like improperly canned food. The toxin attacks the nervous system and can be fatal even in small amounts. Proper pressure canning temperatures and times are the primary defense against botulism in home-preserved food.

Related: Pressure Canner, National Center for Home Food Preservation (NCHFP)

Building Code

A set of regulations governing the design, construction, and maintenance of buildings to ensure safety and structural integrity. Building codes are adopted and enforced at the state or local level, which means protection standards vary significantly by jurisdiction. Major disasters frequently lead to code revisions. The Camp Fire prompted California to adopt the most stringent WUI building codes in the country.

Related: Design Basis, Structural Assessment, Wildland-Urban Interface (WUI)

Bung

The sealed opening on a storage drum, closed with a threaded plug and tightened with a bung wrench. Standard 55-gallon water drums have two bung openings, one 2-inch (NPS) and one 3/4-inch. Pumps, spigots, and siphon tubes thread into the larger bung for filling and dispensing.

Related: HDPE (High-Density Polyethylene), Water Storage

Bureau of Home Economics

A division of the U.S. Department of Agriculture that operated from 1923 to 1962, producing practical, tested guidance on cooking, nutrition, household management, food preservation, and textile care for American families. The Bureau's Depression-era bulletins, written primarily by women scientists, are the foundational source material for the NWS Heritage content series. All Bureau publications are U.S. government works and fully in the public domain.

Related: Aunt Sammy, Hazel Stiebeling, Works Progress Administration (WPA), Federal Writers' Project

Cam-Out

The action of a screwdriver tip climbing out of a screw recess under load instead of continuing to turn it. Phillips fasteners were deliberately shaped to cam out above a certain torque, which is the main reason Phillips screws strip. Square drive and star drive recesses resist it. A tip that fits the recess snugly cams out far less readily than one that is worn or undersized.

Related: Bit Driver

Capability

Having the skills, knowledge, tools, and resources to act effectively when needed. Capability is broader than equipment: a household with a generator but no knowledge of safe operation has equipment, not capability. NWS content is organized around building real capability across twelve self-reliance domains.

Related: Readiness, Resourcefulness, Fieldcraft

Capacity Factor

What a machine actually produced over a period divided by what it would have produced running at full rated output continuously. It is the figure that turns a nameplate rating into a realistic expectation. A 2.5 kilowatt machine producing 3,142 kilowatt-hours in a year is running at a capacity factor of 14.3 percent.

Related: Nameplate Rating, Power Curve, Watt-hour (Wh)

Carbon Monoxide (CO)

A colorless, odorless gas produced by burning fuel (gasoline, propane, natural gas, wood, charcoal) in enclosed or poorly ventilated spaces. Carbon monoxide poisoning is one of the leading causes of death after disasters, primarily from generators, grills, and camp stoves used indoors during power outages. Every household should have battery-operated CO detectors on every floor.

Related: Portable Generator, Power Outage

Cascading Failure

A sequence of failures in an interconnected system where the failure of one component triggers failures in others, often accelerating beyond the system's ability to recover. The 2003 Northeast blackout is a classic example: a software bug and untrimmed trees in Ohio initiated a chain of relay failures that blacked out 55 million people across eight states and Canada. Cascading failures are the primary way that infrastructure systems experience catastrophic events.

Related: Power Grid, Design Basis

Cast Iron Seasoning

Oil baked onto cast iron until it polymerizes and bonds to the metal as a thin, slick coating. It gives bare iron a natural easy-release surface that builds up with regular cooking. When it wears thin or flakes, it can be redone by baking a fresh coat of oil onto the pan in the oven.

Related: Smoke Point, Thermal Shock

Charge Cycle

One full discharge and recharge of a battery's capacity, whether done at once or in partial steps that add up to a full charge. Makers rate batteries for a number of cycles, called cycle life, before they hold noticeably less charge. A higher rating means the battery keeps its runtime through more years of use.

Related: Lithium Iron Phosphate (LiFePO4), Lithium-Ion Battery, Watt-hour (Wh)

Chimney Starter

A metal cylinder that lights charcoal briquettes with a sheet of paper and a match, which shortens the wait for hot coals. Lodge says to light briquettes 15 to 20 minutes before they are needed. Coals are ready when gray ash forms around each one.

Chloramine

A disinfectant that many municipal water systems use in tap water in place of chlorine. Unlike chlorine, it does not off-gas from water left standing, so water meant for fish needs a dechlorinating treatment or an activated carbon filter first. Left untreated, it can harm fish and the microbes in a biofilter.

Related: Chlorine Residual, Biofilter

Collective Efficacy

Neighbors' shared trust in one another combined with their willingness to step in for the good of the neighborhood. The term comes from a 1997 Chicago study by Sampson, Raudenbush, and Earls that linked higher collective efficacy with lower violence. It is the research basis for treating "know your neighbors" as a security measure.

Related: Natural Surveillance

Color Temperature

How warm or cool white light looks, stated in kelvins (K). Lower numbers such as 2700K look yellowish and warm, and higher numbers such as 5000K look bluish and cool. The American Medical Association encourages 3000K or lower for outdoor installations such as roadways to limit glare.

Related: Lumen, Light Trespass

Community Emergency Response Team (CERT)

A FEMA-supported program that trains civilians in basic disaster response skills: fire safety, light search and rescue, first aid, and team organization. CERT volunteers serve as a bridge between professional responders and the community during disasters when emergency services are overwhelmed. Training is free and typically involves 20 hours of instruction through local emergency management agencies.

Related: Incident Command System (ICS), Emergency Operations Center (EOC)

Chlorine Residual

The concentration of chlorine remaining in treated water after initial disinfection. Municipal water plants add chlorine to kill pathogens, and the residual that remains in the water continues to suppress bacterial growth during storage. As the residual dissipates over time, stored water becomes more vulnerable to contamination.

Related: Potable Water, Shelf Life, Water Preserver Concentrate

Chrome Vanadium (Cr-V)

An alloy steel family used widely for hand tools that are turned rather than struck, such as wrenches, sockets, and screwdriver shafts. The marking names the alloy the maker selected. It does not describe heat treatment, dimensional tolerance, or finish, and those are the properties that decide how a tool wears, so the marking is best read as one input rather than a quality grade. Chrome molybdenum, marked Cr-Mo, is more common on tools driven by impact.

Related: Mushroomed Head

Coanda Screen

A self-cleaning intake screen made of inclined wedge wire, angled so that fast-moving flow crossing the surface has thin layers sheared off the bottom and directed through the slots while debris and fish carry on over the panel. The Bureau of Reclamation describes these screens as hydraulically self-cleaning with no moving parts, which suits them to remote sites with no electrical power.

Related: Trash Rack, Forebay, Penstock

Cold Chain

The unbroken series of refrigerated storage and transportation steps that keeps perishable food at safe temperatures from production to consumption. A break in the cold chain, such as a power outage at a warehouse, a refrigerated truck breakdown, or a grocery store losing power, can render large quantities of food unsafe. Most consumers interact with the cold chain only when their own refrigerator loses power.

Related: Just-in-Time Inventory

Communication Tree

A structured system in which one person contacts two or three others, who each contact two or three more, rapidly spreading information through a network without requiring a single point of contact to reach everyone. Communication trees are the most reliable neighborhood-level alert system during events that disrupt cell and internet service. A well-maintained tree can reach 50 households in under 15 minutes using landlines or in-person contact.

Related: Social Capital, Block Captain, Map Your Neighborhood (MYN)

Consignment

An arrangement in which a shop displays and sells your goods and pays you an agreed share of the price only after an item sells. Unsold items remain yours, so the agreement should say who carries loss or damage and when you are paid.

Continuous Output

The sustained power a generator or battery station can supply, as distinct from the total energy it stores. It limits how much can run at the same moment rather than how long anything runs, and planning above about 80 percent of the rating leaves no headroom. A unit rated 1,000 watts continuous should carry a planned load closer to 800.

Related: Startup Surge, Watt-hour (Wh), Inverter

Contract for Deed

A way of buying property in installments in which the seller keeps legal title until the buyer makes the final payment. The buyer usually pays taxes, insurance, and repairs in the meantime, and after a missed payment can lose the property and the money already paid faster than under a mortgage. The Consumer Financial Protection Bureau suggests having an attorney review the contract and recording it with local land records.

Controlled Substance

A drug regulated under federal law because of its potential for misuse or dependence. The DEA sorts these drugs into five schedules based on accepted medical use and that potential. Common prescriptions in this group include oxycodone, hydrocodone combinations, and ADHD medications such as Adderall.

Cool-Season Crop

A vegetable that grows best in cool weather and tolerates a light frost, such as lettuce, spinach, peas, kale, broccoli, or carrots. These are usually planted early in spring and harvested by early summer, or planted again for fall. Warm-season crops such as tomatoes and peppers are damaged by frost and planted after the danger passes.

Related: Plant Hardiness Zone

Cooling Center

A publicly accessible air-conditioned space, often a library, community center, or government building, opened during heat emergencies so that residents without adequate cooling can escape dangerous temperatures. Ready.gov advises seeking another cooling option when home air conditioning is not available.

Related: Heat Index

Cooperative Extension Service

A nationwide network of offices, typically one per county, operated by land-grant universities in partnership with the USDA, providing research-based education in agriculture, food safety, home economics, and community development. Extension offices are where Master Gardener programs, food preservation workshops, and 4-H programs are administered. They are an underused civic resource for household self-reliance.

Related: Bureau of Home Economics, Master Gardener, National Center for Home Food Preservation (NCHFP)

Cooperative Extension Bulletins

Printed educational publications produced by state Cooperative Extension Services, typically at land-grant universities, covering agriculture, food preservation, gardening, home economics, and household management. Depression-era Extension bulletins from the 1930s are a primary source for NWS Heritage content, offering tested, practical guidance from a time when household self-reliance was an economic necessity, not a lifestyle choice.

Related: Cooperative Extension Service, Bureau of Home Economics

COPPA

The Children's Online Privacy Protection Act, a federal law requiring websites and apps to obtain verifiable parental consent before collecting personal information from children under 13. Most major platforms set their minimum account age at 13 because of COPPA. The FTC updated the rule in April 2025.

Related: Data Broker, Password Manager

Cord (of firewood)

A stacked volume of firewood measuring 128 cubic feet, conventionally four feet by four feet by eight feet. It is the standard unit for buying, selling and planning firewood, and because it measures volume rather than weight, the usable energy in one cord varies with species and moisture content. A face cord is not the same thing: it is a single stacked face of that pile, so its volume depends on how long the pieces are cut.

Related: Annual Increment

Cottage Food Law

A state law that lets people sell certain lower-risk foods made in a home kitchen without a commercial food license. Each state sets its own list of allowed foods, where they can be sold, and what the label must say. Some states add a sales cap, a registration or an inspection.

Cardiopulmonary Resuscitation (CPR)

An emergency procedure combining chest compressions and rescue breaths for someone in cardiac arrest, when the heart stops beating or beats too weakly to circulate blood to the brain and vital organs. Started immediately by a bystander, CPR can double or triple the chance of survival.

Related: First Aid, American Red Cross

Crime Prevention Through Environmental Design (CPTED)

An approach to crime prevention that changes how a place is designed and maintained so crime becomes harder to commit and easier to notice. Police and planning departments use it to assess homes, businesses, and public spaces. Its core principles are natural surveillance, natural access control, territorial reinforcement, and maintenance.

Related: Natural Surveillance

Credit Freeze

A setting at each of the three credit bureaus (Equifax, Experian, TransUnion) that blocks new creditors from pulling your credit report. This prevents anyone from opening accounts in your name, even with your Social Security number. Free by federal law and does not affect your credit score.

Related: Data Broker, Fraud Alert

Cubic Feet per Second

The standard unit for stream discharge in the United States, abbreviated cfs. One cubic foot per second equals roughly 449 gallons per minute, a conversion needed whenever a published gauge record is compared against a household measurement. U.S. Geological Survey streamflow data is reported in these units.

Related: Instream Flow, Weir, Hydraulic Head

Curing Salt

A mixture of sodium chloride and sodium nitrite, dyed pink to prevent confusion with regular salt, used in meat curing and some sausage-making to inhibit the growth of Clostridium botulinum. Curing salt is measured precisely because both too little and too much carry risk: too little may not prevent botulism, and too much is toxic. It is not a substitute for cooking or proper refrigeration.

Related: Botulism

Cut-In Wind Speed

The wind speed at which a turbine begins producing usefully. Below it the rotor may turn without generating anything worth counting, which is one reason an estimate based on average wind speed alone overstates output.

Related: Power Curve, Capacity Factor, Wind Shear

Danger Zone (Food Safety)

The temperature range between 40°F and 140°F in which foodborne bacteria multiply most rapidly. Perishable food left in the danger zone for more than two hours, or one hour above 90°F, should be discarded. The rule governs everything from outdoor cooking to power-outage food decisions.

Related: Food Storage

Data Broker

A company that compiles personal information from public records, app data, and online activity into profiles it sells. Data broker profiles can include your name, address history, phone numbers, relatives, and estimated income. You can request removal from most brokers for free.

Related: Credit Freeze, COPPA

Days of Autonomy

The number of days a battery bank can carry its load with no charging input. It is the figure that sizes the bank, because a system built for one cloudy day and one built for four differ mostly in storage cost. Off-grid systems are commonly designed for two to five days depending on climate and how tolerable a shortfall is.

Related: Depth of Discharge (DoD), Lithium Iron Phosphate (LiFePO4), Watt-hour (Wh)

Debris Flow

A fast-moving slurry of water, mud, rocks, and vegetation that flows downhill through channels, often triggered by heavy rain on steep slopes burned by wildfire. Debris flows are among the most lethal secondary hazards following wildfire because they move faster than a person can run and can strike with little warning. The 2018 Montecito debris flow in California, triggered by rain over the Thomas Fire burn scar, killed 23 people.

Related: Landslide, Wildfire

Deductible

The amount you pay toward a covered loss before your insurance pays the rest. A higher deductible lowers the premium but means more of a small loss comes out of your pocket. When a loss is close to the deductible, filing a claim may pay little and can still affect future rates.

Related: Insurance Adjuster, Actual Cash Value (ACV), Replacement Cost

Deepfake

AI-generated or AI-manipulated video, audio, or images designed to look or sound like a real person. Deepfake technology can clone a voice from a few seconds of audio or swap a face onto another person's body in real-time video calls.

Related: Voice Cloning, Phishing

Defensible Space

The buffer zone around a home where vegetation and other combustible materials are managed to slow or prevent the spread of wildfire. Defensible space is the single most effective action a homeowner in the WUI can take to protect their home. Most guidelines recommend three zones extending at least 100 feet from the structure.

Related: Wildland-Urban Interface (WUI), Wildfire, Fire-Adapted Community, Home Hardening

Depth of Discharge (DoD)

The share of a battery's rated capacity actually drawn down before recharging. Usable capacity is always smaller than nameplate capacity, and discharging deeper shortens the number of cycles a bank will deliver. Lead-acid banks are commonly held near 50 percent, while lithium iron phosphate tolerates 80 to 100 percent depending on the manufacturer.

Related: Lithium Iron Phosphate (LiFePO4), Days of Autonomy, Nameplate Rating

Design Basis

The set of conditions (the strongest wind, the highest flood, the coldest temperature) that an engineered system was built to withstand. When an event exceeds the design basis, the system may fail even if it was built and maintained correctly. Many infrastructure failures occur because the design basis was set decades ago using historical data that no longer reflects current risk.

Related: Cascading Failure, Levee, Building Code

Digestate

The material left in an anaerobic digester after the microbes have finished converting feedstock into biogas. It leaves the vessel continuously and in roughly the volume that entered it, so a digester needs somewhere for the digestate to go before it is built. It retains most of the nitrogen from the original feedstock and is commonly applied to land as fertiliser.

Related: Manure Slurry

Disaster Declaration

A formal determination by the President that a disaster has occurred which exceeds state and local capacity to respond, triggering federal assistance. A disaster declaration opens FEMA Individual Assistance for households, Public Assistance for governments, and Hazard Mitigation grants. Not all emergencies receive declarations. The governor must request one and FEMA must assess the damage.

Related: Federal Emergency Management Agency (FEMA), FEMA Individual Assistance (IA), SBA Disaster Loan

Discipline

Maintaining consistent habits and routines that support long-term preparedness and self-reliance. Discipline is the difference between owning a water filter and actually rotating your stored water on schedule. Most preparedness failures are not failures of equipment but failures of maintenance, practice, and follow-through.

Related: Vigilance, Prudence, Operational Readiness

Dissolved Oxygen

Oxygen held in water, usually measured in parts per million (ppm). Fish, plant roots, and the microbes in a biofilter all depend on it, and warmer water holds less of it. Many warm-water fish and plants grown in aquaponics do best at 6 to 7 ppm.

Related: Nitrification, Biofilter

Distribution System

The final stage of the power grid or water supply that delivers service from a local substation or treatment plant to individual homes and businesses. Distribution infrastructure (the poles, wires, pipes, and valves in your neighborhood) is typically the oldest and most vulnerable part of the system. Most power outages originate in the distribution network, not in generation or transmission.

Related: Power Grid, Water Main

Diversion Load

An electrical load, usually a resistance heating element, that receives power a household is not using so a generator always has somewhere to send its output. Hydro and wind systems cannot simply be disconnected from their energy source, so surplus must be consumed rather than refused. The load must be able to absorb the machine's full output continuously, since the case it exists for is total loss of household demand.

Related: Runaway Speed, Inverter

Do-Not-Resuscitate (DNR) Order

A medical order that tells providers not to perform CPR if a person's breathing or heartbeat stops. A doctor writes it after discussing the choice with the patient, or with the patient's proxy or family.

Related: Advance Directive, Health Care Power of Attorney

Down Payment Assistance (DPA)

Grants or low-interest second loans, usually offered through a state or local housing finance agency, that cover part of a homebuyer's down payment or closing costs. Some are forgiven if the buyer stays in the home for a set number of years. Eligibility usually depends on income limits, a purchase price cap, and a homebuyer education course.

Drought

A prolonged period of abnormally low precipitation that creates water shortages affecting agriculture, water supply, and fire risk. The U.S. Drought Monitor classifies drought severity from D0 (abnormally dry) to D4 (exceptional drought). Drought is both a hazard itself and a force multiplier for other hazards: it increases wildfire risk, strains water infrastructure, and can trigger agricultural economic crises.

Related: Wildfire

Duty Cycle

The fraction of time a device actually draws power while it is switched on. Appliances with compressors cycle rather than running continuously, so multiplying watts by hours without it badly overstates energy use. A refrigerator's compressor typically runs about 8 hours out of every 24.

Related: Running Watts, Watt-hour (Wh)

Door Jamb

The vertical sides of a door frame that the door hinges on and latches against. In most homes the jamb is a strip of finished softwood set inside a rougher opening framed with studs, with shims between the two. Because the jamb itself is thin, hinge and strike screws that stop in it hold far less than screws long enough to reach the studs behind it.

Related: Strike Plate, Mortise

Emergency Planning Zone (EPZ)

The area around a nuclear plant where governments pre-plan protective actions. The inner zone, about 10 miles, plans for sheltering, evacuation, and potassium iodide, and plans there are exercised and federally evaluated. Zone maps are public, county by county.

Related: Ingestion Pathway Zone, Potassium Iodide (KI), Shelter in Place

Evacuation Vehicle

A vehicle maintained and equipped specifically for evacuation during an emergency. An evacuation vehicle does not need to be a specialized truck or SUV. Any reliable, well-maintained vehicle with a full fuel tank and an emergency kit serves the purpose for most households.

Related: Evacuation Order, 72-Hour Bag

Earthquake

A sudden shaking of the ground caused by the release of energy along a geological fault. Earthquakes cannot be predicted with useful precision, making preparedness (structural retrofitting, securing heavy objects, and emergency kits) the primary defense. The San Andreas Fault in California and the New Madrid Seismic Zone in the central U.S. are the two most studied high-risk zones.

Related: Seismic Retrofit

Emergency Alert System (EAS)

The national public warning system that broadcasts emergency alerts over radio, television, and cable systems. EAS replaced the older Emergency Broadcast System in 1997 and can be activated at the federal, state, or local level. EAS is the backbone of the national alert infrastructure, though most people now encounter emergency warnings through WEA on their phones.

Related: Wireless Emergency Alert (WEA), NOAA Weather Radio

Enhanced Fujita (EF) Scale

The rating system used to classify tornado intensity based on the damage they produce, ranging from EF-0 (minor damage, 65–85 mph winds) to EF-5 (total destruction, over 200 mph winds). The scale is applied after an event by survey teams who assess structural damage. Only about 1% of U.S. tornadoes reach EF-4 or EF-5 intensity.

Related: Tornado, Supercell

Electromagnetic Pulse (EMP)

A burst of electromagnetic energy that can disable or damage electronic equipment and power systems. EMPs can be caused by lightning, solar storms (geomagnetic disturbances), or nuclear detonation at high altitude. The primary household concern is protecting critical electronics such as radios and medical devices through shielding.

Related: Cascading Failure

Emergency Operations Center (EOC)

The physical or virtual location where emergency management personnel coordinate information, resources, and decision-making during a disaster. Counties, cities, and states each maintain EOCs that activate during significant events. EOCs coordinate with FEMA's regional and national operations centers during federally declared disasters.

Related: Incident Command System (ICS), Federal Emergency Management Agency (FEMA), Community Emergency Response Team (CERT)

Epinephrine Auto-Injector

A prefilled device that injects a measured dose of epinephrine into the outer thigh to treat anaphylaxis, a severe allergic reaction. It is intended for immediate use at the first signs of a reaction and is not a substitute for emergency medical care.

Related: First Aid

Electric Reliability Council of Texas (ERCOT)

The independent grid operator that manages the flow of electricity to roughly 90% of Texas. ERCOT is unique among U.S. grid operators because it is largely isolated from the two national interconnections, meaning Texas cannot easily import power from neighboring states during emergencies. This isolation was a central factor in the February 2021 grid collapse during Winter Storm Uri.

Related: Power Grid, Cascading Failure, Rolling Blackout

Evacuation Order

An official directive from local authorities instructing residents to leave a defined area due to an imminent or ongoing threat. Evacuation orders may be mandatory or advisory, depending on jurisdiction and hazard. In most U.S. states, even mandatory evacuation orders cannot legally force residents to leave, but those who stay may not receive emergency assistance.

Related: Shelter in Place, 72-Hour Bag, Wireless Emergency Alert (WEA)

Exclusion

The practice of physically sealing gaps, cracks, and openings in a building to prevent pests from entering. University extension programs and the EPA identify exclusion as the single most effective component of integrated pest management for homes.

Related: Integrated Pest Management, Harborage

Fair Market Rent (FMR)

The rent the U.S. Department of Housing and Urban Development estimates each year for a standard-quality rental in a metro area or nonmetropolitan county, set at the 40th percentile of local gross rents (rent plus utilities). It sets payment standards for the Housing Choice Voucher program and gives renters a neutral benchmark for what a modest unit should cost in a given place. HUD publishes new figures every federal fiscal year.

Family Communication Plan

A documented plan that ensures every member of a household knows how to reach each other and where to meet if separated during an emergency. The plan should include an out-of-state contact (local lines may be jammed while long-distance calls go through), a meeting place near home, a meeting place outside the neighborhood, and each family member's route from school or work. Write it down, because memory fails under stress.

Related: Communication Tree, 72-Hour Bag, Evacuation Order

Farm Number (FSA)

An identification number the USDA Farm Service Agency assigns to a farm in its records. A farm number is required for many USDA programs, including farm loans and disaster relief. Since the 2018 Farm Bill, operators of heirs' property can establish one with alternative documents when they lack a clear deed.

Related: Heirs' Property

Federal Writers' Project

A WPA program (1935–1943) that employed writers to produce state guidebooks, oral histories, and cultural documentation across the country. The Project's life-history interviews, roughly 2,900 first-person accounts from farmers, factory workers, sharecroppers, and housewives, are a primary source for understanding how ordinary Americans lived, ate, and managed households during the Depression.

Related: Works Progress Administration (WPA), America Eats (WPA), Bureau of Home Economics

Federal Emergency Management Agency (FEMA)

The federal agency responsible for coordinating disaster response, recovery, and preparedness in the United States. FEMA administers Individual Assistance grants, the National Flood Insurance Program, and the public assistance program that reimburses state and local governments after declared disasters. FEMA operates within the Department of Homeland Security.

Related: Disaster Declaration, FEMA Individual Assistance (IA), National Flood Insurance Program (NFIP), SBA Disaster Loan

FEMA App

A free mobile application from the Federal Emergency Management Agency that provides real-time weather alerts, open shelter locations, disaster recovery center information, and preparedness tips. During an active disaster, texting SHELTER and a ZIP code to 43362 provides similar shelter information for users without the app.

Related: Federal Emergency Management Agency (FEMA), Wireless Emergency Alert (WEA)

Field of View (FOV)

The width of the scene a camera lens takes in, usually stated in degrees. A wider field of view covers more area but spreads the same number of pixels across it, so faces and objects at a distance show less detail. Specifications may state it horizontally or diagonally, and the diagonal figure is the larger of the two.

Related: Pixel Density

Fieldcraft

Practical outdoor and hands-on skills that enable a person to operate effectively in non-ideal conditions. Fieldcraft includes fire-starting, basic navigation, shelter construction, water sourcing, knot-tying, and tool use. These skills are learned through practice, not reading, and they transfer across many preparedness scenarios.

Related: Capability, Resourcefulness, Discipline

FIFO (First In, First Out)

An inventory rotation method in which the oldest items are used or consumed first, ensuring nothing expires while newer stock sits in front of it. FIFO is the foundational principle of food storage rotation: place new purchases behind existing stock so the older items get used first. The USDA Bureau of Home Economics taught this system in the 1930s, decades before the acronym existed.

Related: Pantry Discipline, Food Storage, Shelf Life

Fire-Adapted Community

A community in or near the WUI that has taken collective action to reduce its vulnerability to wildfire, including defensible space around homes, fire-resistant building materials, community fuel reduction projects, and practiced evacuation plans. The Firewise USA program, administered by the NFPA, provides a framework for achieving fire-adapted status. The concept shifts responsibility from firefighters alone to the entire community.

Related: Defensible Space, Wildland-Urban Interface (WUI), Wildfire, Building Code

Fire Behavior Triangle

A conceptual model showing the three factors that determine how a wildfire behaves once ignited: fuel (type, moisture, arrangement), weather (wind, humidity, temperature), and topography (slope, aspect, elevation). Fire behavior is most dangerous when all three factors align: dry fuel, hot windy weather, and uphill terrain. The model is the foundation of wildfire prediction and firefighting strategy.

Related: Wildfire, Fuel Load, Red Flag Warning

Fire Door

A door assembly designed and tested to resist the passage of fire and smoke for a rated period (typically 20, 45, 60, or 90 minutes). Fire doors are required in stairwells, corridors, and between fire-rated compartments. They must be self-closing and must not be propped open except with approved automatic-release devices that close the door when the fire alarm activates.

Related: NFPA 101 (Life Safety Code)

Fire Extinguisher (ABC-Rated)

A portable device that discharges an extinguishing agent to put out small fires. ABC-rated extinguishers handle three classes of fire: ordinary combustibles (paper, wood), flammable liquids (grease, oil), and electrical fires. A 2.5-pound ABC dry chemical extinguisher is the most common recommendation for home kitchens.

Related: Smoke Alarm, Grease Fire

Firewise USA

A recognition program administered by the National Fire Protection Association that provides a framework for communities in or near the WUI to organize and take action to reduce wildfire risk. Participating communities complete an assessment, develop a plan, invest in annual mitigation projects, and host educational events. Over 2,000 communities in the U.S. currently hold Firewise USA recognition.

Related: Fire-Adapted Community, Defensible Space, Wildland-Urban Interface (WUI)

Firmware

The built-in software that runs a device such as a camera, router, or smart lock. Makers fix security problems through firmware updates, so a device that stops receiving them stays exposed to flaws that are already known. The FTC advises checking for firmware updates on internet-connected devices at home.

Related: Two-Step Verification

First Aid

The immediate care given to a person who is injured or suddenly ill, before professional medical help arrives. Basic first aid skills (stopping bleeding, treating burns, performing CPR, recognizing stroke and heart attack) are among the most universally useful emergency skills a person can learn. Red Cross and American Heart Association courses provide standardized certification in 4–8 hours.

Related: Community Emergency Response Team (CERT), American Red Cross, Cardiopulmonary Resuscitation (CPR)

First-Flush Diverter

A device installed inline on a rainwater collection downspout that captures and discards the initial flow of water from a rain event before cleaner water enters the storage barrel. The first flush from a roof carries concentrated bird droppings, atmospheric pollutants, and roofing material residue accumulated during dry periods. Discarding this fraction significantly improves the quality of collected rainwater.

Related: Turbidity, Potable

Flood

An overflow of water onto land that is normally dry, caused by heavy rain, snowmelt, storm surge, or dam failure. Flooding is the most common and widespread natural hazard in the United States. Flash floods, meaning rapid flooding within six hours of heavy rain, cause the majority of flood-related deaths.

Related: National Flood Insurance Program (NFIP), Floodplain, Storm Surge

Floodplain

The flat area adjacent to a river or coast that is naturally subject to periodic flooding. FEMA maps floodplains to determine insurance requirements and building restrictions. The commonly used term '100-year flood' means a flood that has a 1% chance of occurring in any given year, not that it happens only once per century.

Related: Flood, National Flood Insurance Program (NFIP)

Food Storage

The practice of maintaining a supply of shelf-stable food in the home for use during disruptions such as power outages, supply chain interruptions, weather events, or income loss. A practical household food store starts with 72 hours of no-cook food and builds toward a 14-day rotating pantry of foods the household already eats. The key principle is rotation: stored food should be consumed and replaced regularly, not packed away and forgotten.

Related: FIFO (First In, First Out), Pantry Discipline

Forebay

A small tank between an intake and a penstock where water slows enough for sand and sediment to settle out before reaching the turbine. It also keeps air out of the pipe when the water level changes suddenly, and provides a place that can be drawn down and cleaned.

Related: Penstock, Trash Rack, Tailrace

Foresight

The practice of anticipating future needs, risks, and conditions before they arrive. Foresight is the foundation of all preparedness: storing water before the outage, reviewing insurance before the storm, building savings before the job loss. It is not prediction; it is the habit of asking what could change and preparing accordingly.

Related: Prudence, Situational Awareness, Readiness

Fortitude

Strength of character and resolve when facing adversity, discomfort, or prolonged difficulty. Fortitude is what sustains a household through a week-long power outage, a months-long recovery, or the steady work of building self-reliance over years. It is built through small, repeated choices to do the harder, more useful thing.

Related: Resilience, Stoicism, Discipline

Fraud Alert

A free notice on your credit report that tells lenders to verify your identity before opening new credit in your name. The credit bureau you contact must tell the other two. An initial fraud alert lasts one year and can be renewed; an extended alert for identity theft victims lasts seven years.

Related: Credit Freeze

Free-Piston (Stirling engine)

A Stirling engine layout in which the pistons are not connected to a crankshaft and instead oscillate on springs or gas pressure. Because no rotating linkage crosses the pressure boundary, the machine can be sealed for life and needs no lubrication, which is why these are the designs that reached commercial production. Power is usually taken out electrically through a linear alternator rather than as shaft rotation.

Related: Regenerator (Stirling engine)

Freeze-Dried Food

A preservation method that removes nearly all moisture from food by freezing it and then reducing pressure so the ice sublimates directly to vapor. Freeze-dried food is lightweight, shelf-stable for 20 to 30 years when sealed with oxygen absorbers, and rehydrates quickly with hot water. It is significantly more expensive per calorie than canned or dehydrated food.

Related: Shelf Life, Food Storage

Freeze-Dried Food

Food preserved by rapidly freezing and then removing moisture through sublimation under vacuum. Freeze-dried foods retain most of their original flavor, nutrients, and texture when rehydrated with water. They are extremely lightweight, have shelf lives of 25 to 30 years when properly packaged, and are a compact option for apartment emergency food storage.

Related: Shelf-Stable Food, Shelf Life

Frost Line

The maximum depth to which the ground freezes in a given climate. Water pipes, well casings, and underground supply lines must be buried below the frost line to avoid freeze damage. Frost line depth ranges from near zero in the Deep South to 6 feet or more in northern states.

Related: Rain Barrel

Fuel Load

The total amount of combustible material (dead leaves, fallen branches, standing dead trees, dense undergrowth) present in a given area of wildland. High fuel loads mean more material for a fire to consume, producing more intense heat and faster spread. A century of fire suppression in U.S. forests has allowed fuel loads to build far beyond historical levels in many ecosystems.

Related: Wildfire, Prescribed Burn, Fire Behavior Triangle

Fujita Scale

The original tornado intensity rating system, used from 1971 to 2007, ranking tornadoes F0 through F5 by the damage they caused. Ratings for tornadoes that struck before 1971 are assigned retroactively by damage survey, so older events carry an estimated rating rather than a measured one. It was replaced by the Enhanced Fujita (EF) scale in February 2007.

Related: Enhanced Fujita (EF) Scale, Tornado

Furling

A protective action in which a small turbine turns itself partly out of the wind as speeds rise, reducing load on the rotor. On many small machines the tail vane is the component that does the furling. It is the most common overspeed protection on small turbines.

Related: Overspeed, Yaw, Pitch Control

FEMA Individual Assistance (IA)

The FEMA program that provides financial assistance to individuals and households affected by a federally declared disaster. IA can cover temporary housing, home repairs, and other serious disaster-related needs not covered by insurance. The maximum IA grant changes annually; applicants must register within 60 days of the disaster declaration.

Related: Federal Emergency Management Agency (FEMA), Disaster Declaration, SBA Disaster Loan

Generator Interlock

A mechanical device installed on a home's electrical panel that prevents a portable generator from back-feeding power into the utility grid, which can electrocute lineworkers. An interlock or transfer switch is required by the National Electrical Code for any generator connected to a home's wiring. Running a generator without one is both illegal and potentially fatal to utility workers restoring power.

Related: Power Grid, Portable Generator

Gravity Filter

A water filtration device that moves water through filter elements using gravity alone, requiring no electricity, pumps, or plumbing connection. Water poured into an upper chamber drips slowly through the filter media into a lower chamber ready to drink. Most household gravity filters use carbon block or ceramic elements and sit on a countertop.

Related: Reverse Osmosis, Hollow Fiber Membrane, NSF/ANSI Certification, PFAS (Per- and Polyfluoroalkyl Substances)

Grease Fire

A fire caused by ignition of cooking oil or grease, typically in a pan on a stovetop. Water must never be applied to a grease fire because it causes a violent steam explosion that spreads burning oil. The correct response is to slide a lid over the pan, turn off the heat, and leave the lid in place until the pan cools completely.

Related: Fire Extinguisher (ABC-Rated), Smoke Alarm

Grid-Down Event

A scenario in which the electrical grid stops delivering power to a region, whether from storm damage, equipment failure, or deliberate shutdown. A grid-down event can last hours or weeks and disrupts water treatment, communications, refrigeration, and heating or cooling. Most preparedness planning treats it as the baseline disruption because so many other systems depend on electricity.

Related: Cascading Failure, Power Bank, Carbon Monoxide (CO)

Ground-Fault Circuit Interrupter (GFCI)

A safety device, usually built into an outlet or breaker, that shuts off power when it detects current leaking to ground. GFCIs are designed to protect people from severe or fatal electric shocks. The National Electrical Code has required them on outdoor receptacles since 1973, and the CPSC advises testing them at least once a month.

Guyed Tower

A tower held upright by tensioned cables anchored to the ground in a circle around its base. It is the least expensive tower type per foot of height, but the anchor circle occupies land that has to stay clear. A guyed 100 foot tower anchors 50 to 75 feet out, taking between 0.18 and 0.41 of an acre.

Related: Hub Height, Setback (Zoning), Frost Line

Harborage

Any location that provides shelter, cover, or nesting opportunity for pests. Common residential harborage includes dense vegetation against foundations, woodpiles near the house, cluttered storage areas, and undisturbed spaces under decks or in crawlspaces. Reducing harborage is a core principle of integrated pest management.

Related: Exclusion, Integrated Pest Management

Hardening

Strengthening a system, structure, or process against failure. A home can be hardened against storms with impact-resistant shutters; a financial position can be hardened with emergency savings; a communication plan can be hardened with backup channels. Hardening is preventive work done before conditions deteriorate.

Related: Resilience, Readiness, Operational Readiness

Hazard Potential Classification

A three-level federal system rating a dam as low, significant or high hazard potential according to the probable loss of life, economic loss and environmental damage that would follow a failure. It describes consequences rather than the condition of the structure, so a well-built dam above an occupied valley is high hazard. A classification can change without the dam changing, if development appears downstream.

Related: Spillway, Impoundment

Hazel Stiebeling

A USDA nutritionist who developed the four-tier dietary framework (liberal, moderate, minimum, restricted) that became the basis for federal food assistance policy. Her 1936 bulletin 'Diets to Fit the Family Income' demonstrated that a family could eat nutritiously at minimal cost, a framework that directly influenced what became the USDA Thrifty Food Plan, the basis for modern SNAP benefits.

Related: Bureau of Home Economics, Thrifty Food Plan, Supplemental Nutrition Assistance Program (SNAP)

HDPE (High-Density Polyethylene)

A rigid, food-safe plastic identified by recycling symbol number 2, used in purpose-built water storage containers, food storage bins, and cutting boards. HDPE does not leach harmful chemicals into water under normal storage conditions and is rated for long-term food and water contact by the FDA. It is the standard material for emergency water storage containers.

Related: Potable

Health Care Power of Attorney

A legal document that names a person, often called a health care agent or proxy, to make medical decisions for someone who cannot make them. It covers health care decisions only, not legal or financial ones.

Related: Advance Directive, Do-Not-Resuscitate (DNR) Order

Heat Tape

An electrical heating element designed to wrap around pipes, valves, or other components to prevent freezing. Heat tape draws power continuously or thermostatically, making it effective but dependent on electricity. Also called heat cable.

Related: Frost Line

Heat Exhaustion

A heat-related illness caused by prolonged exposure to high temperatures, especially when combined with high humidity and physical activity. Symptoms include heavy sweating, cold or clammy skin, nausea, dizziness, headache, and a fast weak pulse. Heat exhaustion can progress to heat stroke if untreated. Move the person to a cool place, apply cool cloths, and have them sip water.

Related: Heat Stroke, Heat Index, Cooling Center

Heat Index

A measure of how hot it feels when relative humidity is combined with the actual air temperature. The National Weather Service uses the heat index to issue excessive heat warnings (heat index of 105 degrees F or above for at least two hours) and heat advisories (heat index of 100 to 104 degrees F). Upper-floor apartments without air conditioning can reach heat index values significantly higher than outdoor conditions.

Related: Heat Stroke, Heat Exhaustion

Heat Stroke

A life-threatening condition in which the body's temperature regulation fails and core temperature rises to 103 degrees F or higher. Symptoms include hot red dry skin, rapid strong pulse, confusion, and loss of consciousness. Heat stroke is a medical emergency. Call 911 immediately and move the person to a cooler environment while waiting for help.

Related: Heat Exhaustion, Heat Index

Heat Wave

A prolonged period of abnormally high temperatures that poses health risks, strains power grids, and can be fatal, especially for elderly people, outdoor workers, and those without air conditioning. Heat is the deadliest weather hazard in the United States in most years, killing more people than hurricanes, tornadoes, and floods combined. The definition varies by region: 95°F in Seattle is more dangerous than 95°F in Phoenix because the population and infrastructure are not adapted to it.

Related: Power Grid, Rolling Blackout, Drought

Heating, Ventilation, and Air Conditioning (HVAC)

Heating, ventilation, and air conditioning: the furnace, heat pump, air conditioner, ducts, and fans that heat, cool, and move air through a home. These systems are among a household's largest energy expenses, and routine filter checks and seasonal service keep them running reliably.

Heirs' Property

Land owned jointly by the descendants of someone whose estate never cleared probate, so the heirs can use it but do not hold clear or marketable title. Without clear title the land is hard to borrow against or sell, and any one co-owner can usually ask a court to partition it. Researchers estimate 3.3 to 5.3 million acres of heirs' property across eleven Southern and Appalachian states.

Related: Tenancy in Common, Partition Action, Uniform Partition of Heirs Property Act (UPHPA), Farm Number (FSA)

Homeowners Association (HOA)

A private governing body in a residential community that sets and enforces rules for properties within its jurisdiction. HOA covenants can restrict gardens, rainwater collection, solar panels, livestock, exterior storage, and other self-reliance activities. Restrictions vary widely and are legally binding on property owners.

Related: Zoning, Setback (Zoning)

Hollow Fiber Membrane

A filtration technology using thousands of tiny tubes with microscopic pores that physically block bacteria, protozoa, and sediment while allowing water molecules to pass through. Hollow fiber filters are the core technology in portable filters like the Sawyer Squeeze and LifeStraw. They can be restored to near-original flow rate by backflushing water through the filter in reverse.

Related: Micron, Backflush, Gravity Filter

Home Hardening

The process of modifying a home's exterior to resist ignition from wildfire embers, radiant heat, and direct flame contact. Key measures include replacing wood shake roofs with Class A rated materials, installing metal mesh over vents, using tempered or multi-pane windows, and removing combustible materials from within five feet of the structure. Research shows that home hardening and defensible space together are more effective than either alone.

Related: Defensible Space, Wildland-Urban Interface (WUI), Building Code, Fire-Adapted Community

Household Hazardous Waste (HHW)

Leftover household products that are toxic, corrosive, ignitable, or reactive. Common examples include paints, solvents, cleaners, motor oil, pesticides, drain openers, and automotive batteries. The EPA recommends disposing of HHW through a local collection program rather than pouring it down a drain or placing it in the regular trash.

Related: Storm Sewer

Hub Height

The height above ground of a turbine's rotor center, which is the height whose wind speed actually determines output. Because wind speed rises with height, hub height matters more to annual production than rotor size on most residential sites.

Related: Wind Shear, Guyed Tower, Rotor Diameter

Hurricane

A large rotating storm system that forms over warm ocean water, with sustained winds of 74 mph or higher. Hurricanes bring a combination of wind, storm surge, inland flooding, and tornadoes that can devastate coastlines and penetrate hundreds of miles inland. The Atlantic hurricane season runs from June 1 through November 30.

Related: Storm Surge, Saffir-Simpson Hurricane Wind Scale, Evacuation Order, National Oceanic and Atmospheric Administration (NOAA)

Hydraulic Head

The vertical distance water falls between an intake and the machine it drives, and the figure that with flow rate determines how much power a site can produce. Gross head is the true drop measured with the water standing still. Net head is what remains after pipe friction takes its share, and it is the number that actually makes power. One pound per square inch of pressure corresponds to 2.31 feet of head.

Related: Cubic Feet per Second, Penstock, Micro-Hydro, Weir

Hypothermia

A dangerous drop in body temperature below 95 degrees F, caused by prolonged exposure to cold. Symptoms include shivering, confusion, slurred speech, drowsiness, and loss of coordination. Older adults, young children, and people with certain chronic conditions are at highest risk. In an apartment that has lost heat, indoor temperatures can drop low enough to cause hypothermia within hours during a winter storm.

Related: Cooling Center

Ingestion Pathway Zone

The roughly 50-mile area around a nuclear plant where planning covers food, milk, and water after a release rather than evacuation. Instructions would cover protecting gardens, wells, and livestock feed. It is a planning boundary, not a danger line.

Related: Emergency Planning Zone (EPZ)

Insurance Adjuster

A professional who inspects property damage after a disaster and determines how much the insurance company will pay on a claim. Adjusters may work for the insurance company (staff adjuster), for the policyholder (public adjuster), or independently. Policyholders have the right to hire a public adjuster to represent their interests, typically for 5–15% of the claim settlement.

Related: National Flood Insurance Program (NFIP)

Incident Command System (ICS)

The standardized management structure used to organize emergency response in the United States. ICS provides a common framework (Incident Commander, Operations, Planning, Logistics, Finance) that allows multiple agencies to work together during any type of incident. Every FEMA-coordinated response and most local emergency responses use ICS.

Related: Emergency Operations Center (EOC), Community Emergency Response Team (CERT), Federal Emergency Management Agency (FEMA)

Immediately Dangerous to Life or Health (IDLH)

The airborne concentration of a substance at which it poses an immediate threat to life, would cause irreversible health effects, or would stop someone escaping unaided. NIOSH publishes an IDLH value for common hazardous gases, and it is the number a measured concentration should be compared against when judging whether a space is survivable. Hydrogen sulfide has an IDLH of 100 parts per million; carbon monoxide has an IDLH of 1,200 parts per million.

Related: Olfactory Fatigue, Producer Gas

Impact Mill

An electric grain mill in which stainless steel fins, spinning at tens of thousands of revolutions a minute, burst grain kernels into flour. Impact mills grind quickly and can grind very fine, but they make flour only, not cracked grain or cereal textures, and they cannot take oily, wet, or fibrous material. They run louder than stone mills; one maker rates its impact mills at 78 to 98 decibels.

Related: Stone Burr Mill, Steel Burr Mill

Impoundment

A body of water held behind a dam or embankment. Impounding water converts a stream's continuous output into power available on demand and can create head on flat ground, at the cost of engineering, permitting and permanent legal liability that a diversion does not carry. FEMA states that dam owners can be fiscally and criminally liable for any failure and the damages that follow.

Related: Spillway, Hazard Potential Classification, Run-of-River

Impulse Turbine

A water turbine driven by the velocity of a jet striking its runner in open air, rather than by pressure across submerged blades. The runner is not immersed and the casing carries no pressure, which makes these the simplest machines to build and inspect. Pelton, Turgo and cross-flow turbines are impulse designs, and they suit high-head sites with modest flow.

Related: Reaction Turbine, Runaway Speed, Hydraulic Head

Independence

Freedom from dependence on systems, services, or other people for essential needs. Independence in preparedness is practical, not ideological. It means a household can provide its own water, power, heat, food, and communication for a meaningful period when normal supply is interrupted. Full independence is rare; meaningful independence is achievable.

Related: Autonomy, Self-Sufficiency, Resilience

Induction Cooktop

A cooktop that heats the pan itself with a magnetic field instead of heating the burner surface. It works only with cookware made of ferrous, iron-containing metal, which is why cast iron is a natural fit.

Related: Thermal Shock

Instream Flow

The quantity of water that must remain in a stream channel rather than being diverted, set by state regulators to protect fish, aquatic habitat and downstream users. For anyone planning a diversion it is the figure that matters most, because the permitted design flow is what remains after the instream requirement is met rather than what the stream carries.

Related: Riparian Rights, Prior Appropriation, Cubic Feet per Second

Integrated Pest Management

A prevention-first approach to pest control that prioritizes exclusion, sanitation, and habitat modification before considering chemical treatments. IPM programs use information about pest biology to choose the safest, most effective methods. The EPA describes it as an environmentally sensitive, common-sense approach.

Related: Exclusion, Harborage, Vector

Inverter

A device that converts direct current from a battery or solar panel into the alternating current household appliances use. Inverter quality determines what can safely be run, since sensitive electronics and variable-speed motors need a clean waveform. Conversion is not free, and roughly 10 to 15 percent of stored energy is lost as heat.

Related: Continuous Output, Watt-hour (Wh), Solar Panel

IP Rating (Ingress Protection)

A two-digit code from the international standard IEC 60529 that describes how well an enclosure keeps out solids and water. The first digit covers solids, where 5 means dust-protected and 6 means dust-tight. The second covers water, where 5 means protected against water jets, 6 against powerful water jets, and 7 against temporary immersion.

Just-in-Time Inventory

A supply chain strategy in which goods are delivered to stores and warehouses only as they are needed, minimizing storage costs but reducing the buffer against disruption. Most U.S. grocery stores operate on a 3-day just-in-time cycle, meaning the store's shelves represent roughly three days of normal demand. Any disruption to transportation, distribution, or demand patterns can empty shelves within days.

Related: Cold Chain

Kilowatt-hour (kWh)

A unit of energy equal to 1,000 watt-hours, used on electric bills to measure total electricity consumed over a billing period. One kilowatt-hour is the energy drawn by a 1,000-watt appliance running for one hour. The average U.S. household uses roughly 900 kilowatt-hours per month.

Related: Watt-hour (Wh), Smart Meter

Landslide

The downslope movement of rock, soil, or debris driven by gravity, often triggered by heavy rainfall, earthquakes, or wildfire that destroys stabilizing vegetation. Post-wildfire landscapes are especially vulnerable to debris flows because the burned soil repels water instead of absorbing it. Landslides cause an average of 25–50 deaths per year in the U.S. and billions in property damage.

Related: Wildfire, Earthquake, Flood

Levee

An earthen or concrete embankment built along a waterway to contain floodwater and protect adjacent land. Levees are designed to a specific capacity; when a flood exceeds that design basis, the levee can be overtopped or may fail structurally. The U.S. has roughly 30,000 miles of levees, and the Army Corps of Engineers rates many as deficient.

Related: Floodplain, Flood, Design Basis

Light Trespass

Outdoor light that falls where it is not wanted or needed, such as into a neighbor's window or across a property line. It is a common source of complaints about bright security lighting. Shielded fixtures aimed down keep light on the area they are meant to cover.

Related: Color Temperature

Lithium Iron Phosphate (LiFePO4)

A lithium battery chemistry used widely in solar storage and portable power stations. It tolerates deeper discharge and delivers far more cycles than lead-acid, at a higher cost per unit of capacity. Most LiFePO4 batteries must not be charged below freezing unless they carry an internal heater, though they can usually be discharged well below it.

Related: Depth of Discharge (DoD), Days of Autonomy

Lithium-Ion Battery

A family of rechargeable batteries that store energy by moving lithium ions between two electrodes. Phones, laptops, power banks, and many portable power stations and CPAP batteries use it. Lithium iron phosphate (LiFePO4) is one type, chosen for its longer cycle life.

Related: Lithium Iron Phosphate (LiFePO4), Charge Cycle, Watt-hour (Wh)

Listeria

A bacterium that can grow even in refrigerated conditions, unlike most foodborne pathogens, making it a particular concern in soft cheeses, deli meats, and unpasteurized dairy. Listeriosis, the illness it causes, is especially dangerous for pregnant women, older adults, and people with weakened immune systems. Careful pasteurization and proper aging are the main defenses in home food preparation.

Local Emergency Planning Committee (LEPC)

The public body each county belongs to under federal right-to-know law that keeps chemical inventories and emergency plans for the facilities in its area. Its meetings are open, and it is a resident's most local source for chemical-risk information.

Related: Tier II Inventory

Locked-Rotor Amps (LRA)

The current a motor draws at the instant it starts, before the rotor begins to turn. Some appliance nameplates print it, and where they do it is the authoritative figure for startup demand rather than any general multiplier. It is a worst case, so real starting draw is usually briefer and lower.

Related: Startup Surge, Nameplate Rating

Low Water Condition

The state of a boiler in which the water level falls below the top of the heated surfaces, leaving metal in contact with steam rather than liquid. The exposed metal overheats and loses strength quickly, and a failure at that point releases the stored energy of the entire vessel at once. National Board incident data attributes the large majority of boiler accidents to low water condition and operator error.

Related: Nonstandard Vessel, Rankine Cycle

Lumen

The unit for how much light a bulb or fixture gives off. More lumens means brighter, while watts only describe how much energy it uses. A traditional 60-watt incandescent bulb gives about 800 lumens, and an LED can match that at about 9 watts.

Related: Color Temperature

Manure Slurry

Manure mixed with enough water to be pumped and handled as a liquid rather than a solid. Anaerobic digesters are usually fed this way, because the microbes work in a wet environment and pumpable feedstock can be moved without handling it by hand. Dairy operations commonly manage manure as slurry at a few percent solids.

Related: Digestate

Map Your Neighborhood (MYN)

A community preparedness program that organizes neighbors into small groups (typically 15–20 households) to identify skills, resources, and vulnerabilities on their block before a disaster occurs. MYN was developed by the Washington State Emergency Management Division and has been adopted by communities across the country. The program takes about two hours to complete and produces a resource map, contact list, and simple action plan.

Related: Communication Tree, Social Capital, Block Captain, Community Emergency Response Team (CERT)

Master Gardener

A trained volunteer who completes 40–100 hours of horticultural education through a state's Cooperative Extension Service and then provides gardening advice and community education in return. Master Gardener programs exist in all 50 states and are free or low-cost to participants. They are one of the most accessible civic on-ramps for learning food production skills.

Related: Cooperative Extension Service

Mental Load

The unseen work of noticing what a household needs, planning ahead, remembering deadlines, and coordinating who does what, as distinct from carrying out the tasks themselves. It matters because this work rarely appears on a chore list, so it tends to pile onto one person without anyone deciding that it should.

Micro-Hydro

Small-scale hydroelectric generation, defined by the Department of Energy as systems producing up to 100 kilowatts. Most household installations fall far below that. Its distinguishing advantage over solar and wind is that it generates continuously, so a modest output multiplied by every hour of the year can exceed a much larger intermittent system.

Related: Run-of-River, Hydraulic Head, Penstock

Microchip (Pet ID)

A tiny electronic chip, about the size of a grain of rice, implanted under a pet's skin that contains a unique identification number. When scanned at a shelter or veterinary office, the number links to the owner's contact information in a national registry. The ASPCA recommends microchipping as a permanent form of pet identification that cannot be lost or removed like a collar tag.

Micron

A unit of measurement equal to one millionth of a meter, used to describe the pore size of water filters. A filter's micron rating indicates the smallest particle it will physically block: a 0.1-micron filter blocks bacteria and protozoa, while a 0.2-micron filter blocks protozoa but may allow some bacteria through. Viruses, at 0.02 to 0.3 microns, pass through most hollow fiber filters.

Related: Hollow Fiber Membrane, Gravity Filter, Reverse Osmosis

Mold Remediation

The process of identifying, containing, and removing mold growth from a building after water damage. Mold can begin growing within 24–48 hours of water intrusion and poses respiratory health risks, especially for children, elderly people, and those with asthma. Professional remediation is recommended when mold covers more than 10 square feet or is found inside wall cavities or HVAC systems.

Related: Structural Assessment

Moleskin

An adhesive-backed cotton padding applied over pressure points to prevent and cushion blisters. Common in hiking and travel kits; a few sheets weigh almost nothing and can be cut to size.

Related: First Aid

Maximum Power Point Tracking (MPPT)

A charge controller design that continuously adjusts the load it places on a solar array so the panels operate at their most productive combination of voltage and current. It lets a high-voltage array charge a lower-voltage battery bank without wasting the difference. MPPT controllers typically recover more energy than PWM controllers, with the largest gains in cold weather and low light.

Related: Pulse Width Modulation (PWM), Open-Circuit Voltage (Voc), Solar Panel

Mushroomed Head

The spread, curled edge that forms on the struck end of a chisel, wedge, punch, or drift pin after repeated hammer blows. A mushroomed head can shatter on impact and send sharp fragments toward the user and anyone nearby, which is why federal workplace rules require impact tools to be kept free of them. The safe response is to stop using the tool until the head has been dressed back to a clean profile, or to replace it.

Related: Chrome Vanadium (Cr-V)

Mutual Aid

A practice of reciprocal support in which community members voluntarily share resources, skills, and labor based on need rather than charity. Mutual aid networks are peer-to-peer (participants both give and receive), distinguishing them from top-down charitable organizations. Historical examples include Depression-era cooperative buying clubs, community canning centers, and church dinner rotations.

Related: Social Capital, Communication Tree

Mortise

A pocket or recess cut into wood so that hardware sits flush with the surface. Hinges, strike plates, and the bodies of some locks are mortised into the door or the jamb, usually with a chisel or a router. Reinforcement hardware often needs a deeper or wider mortise than the part it replaces.

Related: Door Jamb, Strike Plate

N95 Respirator

A close-fitting face covering that, when approved by NIOSH, filters at least 95 percent of airborne particles. The "N" means it is not resistant to oil. It protects as intended only when it seals to the face, so follow the maker's instructions and do a seal check each time you put it on.

Nameplate Rating

The maximum power draw printed on an appliance label, measured with every feature operating at once. It is a wiring and safety figure rather than a consumption figure, so sizing from it leads to buying far more capacity than needed. For motor-driven appliances it can be three to four times the running draw.

Related: Running Watts, Locked-Rotor Amps (LRA)

National Pipeline Mapping System (NPMS)

The federal public map viewer showing hazardous liquid and gas transmission pipelines by county. It does not show the smaller distribution lines that serve neighborhoods, which is one reason the 811 call exists.

Related: 811 (Call Before You Dig)

Nitrification

The two-step process in which microbes convert ammonia into nitrite and then into nitrate. In an aquarium or aquaponic system it turns fish waste, which is toxic to fish, into a form plants can use. Ammonia and nitrite both harm fish, so a new system has to establish nitrification before it carries a full load of fish.

Related: Biofilter, Dissolved Oxygen

National Poultry Improvement Plan (NPIP)

A voluntary federal-state program that tests and certifies poultry breeding flocks, hatcheries, chicks, and hatching eggs as free of certain diseases. The diseases covered include several Salmonella strains, Mycoplasma, and avian influenza. CDC advises buying backyard poultry from participating hatcheries to reduce Salmonella in baby birds. The program began operating in 1935.

Related: Biosecurity, Avian Influenza (Bird Flu)

Natural Surveillance

A CPTED principle: arranging lighting, landscaping, and sight lines so people can easily see what happens around a building. Someone approaching a door is more likely to be noticed when the entry is lit and visible from the street or a neighbor's window. Lighting entry points and trimming shrubs that block views of doors and windows are common examples.

Related: Crime Prevention Through Environmental Design (CPTED)

National Center for Home Food Preservation (NCHFP)

The USDA-funded research center at the University of Georgia that develops and maintains the current science-based guidelines for safe home food preservation. NCHFP recommendations are the definitive authority on canning times, pressures, and methods in the United States. Any historical preservation recipe should be cross-checked against NCHFP guidelines before use.

Related: Pressure Canner, Water-Bath Canning

National Flood Insurance Program (NFIP)

The federal program that provides flood insurance to property owners, renters, and businesses in participating communities. Standard homeowner's insurance does not cover flood damage. NFIP policies are typically the only source of flood coverage for most households. NFIP policies have a 30-day waiting period before coverage takes effect.

Related: Flood, Floodplain, Federal Emergency Management Agency (FEMA)

Nationally Recognized Testing Laboratory (NRTL)

A private testing lab that OSHA recognizes to certify products against safety standards. An NRTL's mark on a product shows the lab tested it and found it meets one or more product safety standards. OSHA publishes the current list of recognized labs.

Related: UL (Underwriters Laboratories)

Network Video Recorder (NVR)

A recorder that stores video from networked security cameras on its own hard drive, usually inside the home. It lets several cameras record continuously without a cloud subscription. Because every camera's footage sits in one box, taking or destroying the recorder removes all of it.

Related: Power over Ethernet (PoE)

NFPA 1 (Fire Code)

The broad fire prevention code published by the National Fire Protection Association, covering building maintenance, fire safety equipment, hazardous materials, and occupant safety. NFPA 1 includes the prohibition on open-flame grills on apartment balconies or within 10 feet of multifamily buildings.

Related: NFPA 72 (National Fire Alarm and Signaling Code), Building Code

NFPA 101 (Life Safety Code)

The model building code published by the National Fire Protection Association that establishes minimum requirements for egress, fire protection, and life safety in buildings. NFPA 101 requires that exit routes be continuously maintained free of obstructions, prohibits storage in stairwells, and sets standards for fire doors, emergency lighting, and areas of rescue assistance.

Related: NFPA 1 (Fire Code), NFPA 72 (National Fire Alarm and Signaling Code), Building Code, Fire Door

NFPA 72 (National Fire Alarm and Signaling Code)

The U.S. standard governing the installation, inspection, testing, and maintenance of fire alarm systems, smoke alarms, carbon monoxide alarms, and emergency communication systems. NFPA 72 specifies where smoke alarms must be placed in residential units and how often building fire alarm systems must be tested.

Related: Smoke Alarm, NFPA 1 (Fire Code)

National Oceanic and Atmospheric Administration (NOAA)

The federal science agency responsible for monitoring oceans, atmosphere, and climate, and for providing weather and climate data. NOAA is the parent agency of the National Weather Service, the National Hurricane Center, and the Storm Prediction Center. NOAA satellites provide the imagery and data that power most weather forecasting in the United States.

Related: National Weather Service (NWS), NOAA Weather Radio

NOAA Weather Radio

A nationwide network of radio stations that broadcast continuous weather information directly from National Weather Service offices. Weather radios can be programmed to sound an alarm for specific hazards in your county, such as severe thunderstorms, tornadoes, flash floods, and other warnings. It is the only alert system that works without internet or cell service.

Related: Wireless Emergency Alert (WEA), Red Flag Warning, National Weather Service (NWS)

Nonstandard Vessel

A pressure vessel built without the third-party inspection required for a code stamp. Certification under the boiler and pressure vessel code happens during manufacture, so it cannot be obtained afterwards for a vessel that has already been built. Most jurisdictions will not permit a nonstandard vessel to be operated, which is the practical barrier to a homemade boiler however well it is made.

Related: Low Water Condition

NSF/ANSI Certification

An independent product certification issued by NSF International verifying that a water treatment device meets specific performance standards. Each standard number covers different contaminants: NSF 42 covers taste and odor, NSF 53 covers health contaminants including PFAS when specifically listed, and NSF 58 covers reverse osmosis systems. A product certified to one standard is not automatically certified to others.

Related: PFAS (Per- and Polyfluoroalkyl Substances), Gravity Filter, Reverse Osmosis

National Weather Service (NWS)

The federal agency within NOAA responsible for weather forecasting, severe weather warnings, and climate monitoring in the United States. The NWS operates 122 local forecast offices that issue watches, warnings, and advisories for their respective regions. NWS forecasters are the source of tornado warnings, hurricane forecasts, flood watches, Red Flag Warnings, and winter storm alerts.

Related: National Oceanic and Atmospheric Administration (NOAA), NOAA Weather Radio, Red Flag Warning, SKYWARN

Olfactory Fatigue

The loss of the ability to smell a substance after continued exposure to it, even though the substance is still present. It makes smell an unreliable warning for any gas that causes it, because the warning fades as exposure continues. Hydrogen sulfide causes olfactory fatigue at around 100 parts per million, which is also its immediately dangerous concentration.

Related: Immediately Dangerous to Life or Health (IDLH)

Open-Circuit Voltage (Voc)

The voltage a solar panel or string produces when nothing is connected to draw current. It is the highest voltage the array will ever present, and it rises as temperature falls, which is what limits how many panels can be wired in series. String length is calculated against the record low temperature for the site rather than an average.

Related: Maximum Power Point Tracking (MPPT), Solar Panel, Voltage Drop

Operational Readiness

Being fully capable of acting immediately when conditions require it. Operational readiness means supplies are accessible, equipment is tested and maintained, plans are current, and household members know their roles. It is the difference between having a plan and being ready to execute it right now.

Related: Readiness, Discipline, Capability

Overshot Wheel

A waterwheel fed from above, where water enters buckets at the top and turns the wheel by its weight as it descends. The most efficient of the traditional wheel arrangements, reaching around 85 percent in measured tests, and the one needing the most drop. Wheel diameter is set by available head, which is why overshot wheels are generally used where the fall is no more than about six meters.

Related: Waterwheel, Hydraulic Head

Overspeed

A condition in which a rotor turns faster than its design limit, usually because the electrical load that normally restrains it has been lost. An unloaded rotor can accelerate until it destroys itself, which is why a second independent means of preventing overspeed is required where a diversion load controller is the primary protection.

Related: Diversion Load, Furling, Pitch Control

Pantry Discipline

The systematic practice of maintaining, rotating, and inventorying a household food supply so that nothing expires unused and staples are always available. Pantry discipline includes FIFO rotation, regular inventory checks, purchasing based on what's actually used (not aspirational), and seasonal restocking. The USDA Bureau of Home Economics taught these systems in the 1930s as basic household economics.

Related: FIFO (First In, First Out), Food Storage, Shelf Life

Partition Action

A lawsuit in which a co-owner asks a court to end shared ownership of a property, either by physically dividing the land (partition in kind) or by selling it and splitting the proceeds (partition by sale). Any one co-owner can usually file without the others' consent. Partition sales have historically brought below-market prices, one reason many states adopted the Uniform Partition of Heirs Property Act.

Related: Heirs' Property, Tenancy in Common, Uniform Partition of Heirs Property Act (UPHPA)

PASS Technique

The standard method for operating a portable fire extinguisher: Pull the pin, Aim at the base of the fire, Squeeze the handle, Sweep side to side. A small extinguisher empties in roughly 8 to 12 seconds, so learning the sequence before an emergency is essential.

Related: Fire Extinguisher (ABC-Rated)

Passive Infrared (PIR) Sensor

The most common motion sensor in security lights and battery-powered cameras. It responds to changes in infrared energy, the heat given off by people, animals, and engines, as they move through its view. Sun-warmed branches and warm air from vents can also set it off.

Passkey

A login method that replaces your password with your device's own screen lock, such as a fingerprint or face scan. Passkeys cannot be phished because there is no password to steal. They are supported by most major platforms and are recommended by CISA as phishing-resistant authentication.

Related: Two-Step Verification, Password Manager, Phishing

Password Manager

A program that generates, stores, and fills in a unique password for every account you use. You remember one master password or use your device's biometric login; the manager handles the rest. Most cost between zero and five dollars per month.

Related: Passkey, Two-Step Verification, Recovery Code

Peak Sun Hours

The number of hours per day that sunlight would need to fall at the standard test intensity of 1,000 watts per square metre to deliver the same total energy a site actually receives. It converts a location's sunlight into one figure that can be multiplied by array size to estimate output. Nine hours of winter daylight is not nine peak sun hours, and treating it that way overstates winter production several times over.

Related: Solar Panel, Watt-hour (Wh)

Penstock

The pressure pipe carrying water from an intake down to a turbine. Its diameter governs how much of a site's head survives the trip, because friction rises steeply as bore falls, and it is usually the largest single cost in a micro-hydro project. Common practice is to size it so friction costs no more than 10 to 15 percent of gross head.

Related: Hydraulic Head, Forebay, Water Hammer, Run-of-River

PET (Polyethylene Terephthalate)

Polyethylene terephthalate, the thin, clear plastic used in commercially bottled water and soft drink bottles. PET is lighter and less durable than HDPE and degrades faster under heat and UV exposure. Research has shown that sustained high temperatures can promote leaching of antimony from PET containers.

Related: HDPE (High-Density Polyethylene), Shelf Life

PETS Act (Pets Evacuation and Transportation Standards)

Federal legislation enacted in 2006 requiring state and local emergency management agencies to include household pets and service animals in their emergency evacuation and sheltering plans. The act was prompted by the abandonment of pets during Hurricane Katrina. It does not guarantee every shelter will accept pets, but it requires jurisdictions to plan for them.

Related: Federal Emergency Management Agency (FEMA)

PFAS (Per- and Polyfluoroalkyl Substances)

A group of more than 12,000 synthetic chemical compounds used in industrial processes and consumer products since the 1940s. PFAS do not break down naturally in the environment or the human body, earning the name 'forever chemicals.' Exposure through drinking water has been linked to thyroid disruption, immune system effects, and elevated risk of certain cancers.

Related: NSF/ANSI Certification, Reverse Osmosis, Gravity Filter

pH

A measurement of acidity or alkalinity on a scale of 0 to 14, with lower numbers indicating higher acidity. In home food preservation, pH determines which canning method is safe: foods at pH 4.6 or below can be safely water-bath canned, while foods above that threshold require pressure canning to destroy botulism spores. Testing pH matters most when a recipe adds acid to a naturally low-acid food.

Related: Water-Bath Canning, Pressure Canner, Botulism

Phishing

A scam in which an attacker sends a message, usually by email or text, designed to trick you into clicking a link, entering your password, or providing personal information. Phishing messages often impersonate banks, government agencies, or companies you use.

Related: Two-Step Verification, Passkey, Deepfake

Pitch Control

A mechanism that rotates a turbine's blades about their long axis to change the angle they present to the wind. Pitching regulates power output and limits rotor speed in high wind. It is more common on large machines than on small residential turbines.

Related: Overspeed, Furling, Yaw

Pixel Density

How many image pixels fall across each foot or meter of a scene at a given distance from a camera. It decides whether video can only show that a person is present or can identify who they are. The international guideline IEC 62676-4 sets identification at about 250 pixels per meter, roughly 76 pixels per foot.

Related: Field of View (FOV)

Plant Hardiness Zone

A geographic band on the USDA Plant Hardiness Zone Map, based on the average annual extreme minimum winter temperature at a location. Gardeners use it to judge which perennial plants are likely to thrive there over winter. The 2023 edition divides the country into 10-degree Fahrenheit zones, each split into 5-degree half zones.

Related: Cool-Season Crop, Cooperative Extension Service

Portable Generator

A fuel-powered engine that produces electricity for temporary use during a power outage. Portable generators can power essential appliances (refrigerators, medical devices, lights, phone chargers) but must be operated outdoors due to carbon monoxide risk. Carbon monoxide from generators kills more people after hurricanes than the storms themselves in many events.

Related: Generator Interlock, Power Grid, Carbon Monoxide (CO)

Portable Power Station

A rechargeable battery unit with built-in AC outlets, USB ports, and sometimes 12V outputs, used to power devices during outages or off-grid situations. Unlike portable generators, power stations produce no exhaust and are safe to use indoors. Capacity is measured in watt-hours; a 500Wh unit can run a phone, lights, and a small fan for roughly a full day.

Related: Watt-hour (Wh), Solar Panel

Positive Identification

The practice of confirming a wild plant, mushroom, or other foraged food matches a single edible species with total certainty, using multiple physical characteristics rather than a partial resemblance. Positive identification is the foundational discipline of foraging, because look-alike species can be mildly unpleasant or fatally toxic. The rule among experienced foragers is simple: never eat on a maybe.

Potable

Safe for human consumption, meaning the water has been treated, tested, or verified to be free of harmful biological and chemical contaminants at levels exceeding health standards. Tap water from a public water system is potable; untreated surface water from a stream or rain barrel is not.

Related: Boil Water Advisory, Gravity Filter, Reverse Osmosis

Potable Water

Water that is safe to drink, cook with, and use for personal hygiene without risk of illness. Municipal tap water in the U.S. is treated to potable standards, but that treatment depends on functioning infrastructure: power to run treatment plants, intact distribution pipes, and chemical supply chains. When any of those fail, tap water may no longer be potable, and a boil water advisory or do-not-use order is issued.

Related: Boil Water Advisory, Water Storage

Potassium Iodide (KI)

A medication that protects the thyroid gland from radioactive iodine during a nuclear emergency. It protects nothing else, works best within three to four hours of exposure, and should be taken only when public health officials direct it.

Related: Emergency Planning Zone (EPZ)

Power Curve

A manufacturer's chart of how much power a specific turbine produces at each wind speed. Run against a measured speed distribution for the site, it is the honest way to estimate annual output. Published curves are produced in smooth, low-turbulence air, so real sites generally fall short of them.

Related: Capacity Factor, Cut-In Wind Speed, Turbulence

Power Bank

A small rechargeable battery designed to charge phones, tablets, and other USB-powered devices away from an outlet. Capacity is measured in milliamp-hours (mAh); a 10,000 mAh power bank can fully charge most smartphones two to three times. An essential item in any apartment 72-hour bag.

Related: Portable Power Station

Power Grid

The interconnected network of generation plants, transmission lines, and distribution systems that delivers electricity from producers to consumers. The U.S. grid operates as three major interconnections (Eastern, Western, and ERCOT in Texas) that function largely independently. The grid is the single most complex machine in the country, with roughly 160,000 miles of high-voltage transmission lines.

Related: Cascading Failure, Electric Reliability Council of Texas (ERCOT), Rolling Blackout, Generator Interlock

Power Outage

An unplanned loss of electrical service to a home or area, caused by weather, equipment failure, or a disturbance on the grid. Outages interrupt heating and cooling, refrigeration, water pumping on well systems, and any medical equipment that runs on household current. Duration is what changes the household response: a few hours is an inconvenience, while a multi-day outage becomes a food safety, temperature, and medical continuity problem.

Related: Rolling Blackout, Power Grid, Cascading Failure, Generator Interlock

Power over Ethernet (PoE)

A way of sending electrical power and network data down a single Ethernet cable. A security camera or wireless access point on PoE needs no outlet of its own and no Wi-Fi connection. The method is defined in the IEEE 802.3 family of networking standards.

Related: Network Video Recorder (NVR)

Prescribed Burn

A planned, intentionally set fire used to manage vegetation, reduce fuel loads, and restore fire-dependent ecosystems. Prescribed burns are conducted under specific weather conditions by trained crews with containment resources in place. Decades of fire suppression have created a prescribed burn deficit: the backlog of land that needs burning far exceeds current capacity.

Related: Wildfire, Defensible Space, Fuel Load

Pressure Canner

A specialized piece of kitchen equipment that processes food in sealed jars at temperatures above 240°F, the temperature required to destroy Clostridium botulinum spores in low-acid foods like vegetables, meat, and poultry. A pressure canner is not the same as a pressure cooker; canners are larger, have a pressure gauge or weighted regulator, and are tested to specific standards. Pressure canning is the only safe method for home preservation of low-acid foods.

Related: National Center for Home Food Preservation (NCHFP), Water-Bath Canning

Prior Appropriation

The water law tradition followed in most western states, under which rights are allocated by seniority of first beneficial use rather than by land ownership. First in time, first in right: a senior holder downstream is entitled to their full allocation before a junior holder upstream may take any. Rights are tied to beneficial use and can be lost through non-use.

Related: Riparian Rights, Instream Flow

Producer Gas

The fuel gas made by burning a solid fuel with a restricted air supply, so that carbon burns to carbon monoxide rather than carbon dioxide. It will run an internal combustion engine, but it runs roughly 15 to 22 percent carbon monoxide by volume, far above the concentration at which carbon monoxide is immediately dangerous. Once the gas has been cleaned it carries no odour of its own, so a leak gives no warning.

Related: Syngas (Synthesis Gas), Tar Cracking, Immediately Dangerous to Life or Health (IDLH)

Proof of Loss

A signed statement, sometimes sworn, that lists what you lost and the dollar amount you are claiming. Insurers often require one before paying a claim, and policies set a deadline for sending it.

Related: Insurance Adjuster, Deductible

Prudence

Making careful, forward-thinking decisions that account for future consequences. Prudent preparedness means building capability steadily rather than panic-buying, choosing reliable equipment over the cheapest option, and maintaining what you have before acquiring more.

Related: Foresight, Discipline, Sustainability

Paralytic Shellfish Poisoning (PSP)

A serious, sometimes fatal illness caused by eating shellfish that have accumulated toxins produced by certain algae blooms, commonly called red tide. PSP toxins are not destroyed by cooking, which is why shellfish harvesting depends on checking official closure status before every outing rather than on any preparation method. Symptoms can begin within minutes and progress to respiratory paralysis in severe cases.

Related: Danger Zone (Food Safety)

Pulse Oximeter

A small device, usually clipped on a fingertip, that uses light to estimate the oxygen level in the blood without drawing blood. Readings can be less accurate with poor circulation, darker skin pigmentation, thick or cold skin, tobacco use, or nail polish. The FDA advises against relying on one alone; watch symptoms too.

Pulse Width Modulation (PWM)

A simpler charge controller design that connects the solar array almost directly to the battery and regulates charging by switching that connection on and off rapidly. The array is pulled down to battery voltage, so panel voltage above that is lost rather than converted. PWM controllers cost less and suit small systems where panel and bank voltages already match closely.

Related: Maximum Power Point Tracking (MPPT), Solar Panel

Rain Barrel

A container that captures and stores rainwater from a roof's gutter system for later use in irrigation, cleaning, or emergency water supply. Rain barrels are legal in most U.S. states, though some states regulate the volume that can be collected. A single barrel typically holds 50–80 gallons; the water is not potable without treatment.

Related: Water Storage

Rankine Cycle

The thermodynamic cycle used by steam plant, in which a liquid is boiled, expanded through a turbine or engine to produce work, condensed back to liquid, and pumped back to the boiler. It is how almost all thermal power stations turn heat into electricity, at any scale. The organic Rankine cycle is the same arrangement using a fluid that boils below the temperature of water, which lets it run on lower grade heat.

Related: Low Water Condition

Reaction Turbine

A water turbine that runs full of water, with every blade in contact with it, taking power from the pressure drop across the runner rather than from a jet. Propeller, Kaplan and Francis machines belong to this family, along with pumps run backward. They suit lower head with higher flow and generally deliver more power from a smaller machine than an impulse design.

Related: Impulse Turbine, Hydraulic Head

Readiness

The state of being equipped, informed, and mentally prepared to respond to challenges or emergencies. In a preparedness context, readiness means having plans, supplies, skills, and the calm confidence to act when conditions change.

Related: Resilience, Operational Readiness, Capability

Recovery Code

A one-time-use code provided when you enable two-step verification. Recovery codes let you regain access to your account if you lose your phone or authenticator app. Store them in a printed list or your household account inventory, not on the device they protect.

Related: Two-Step Verification, Password Manager

Red Flag Warning

A forecast alert issued by the National Weather Service when weather conditions are especially favorable for wildfire ignition and rapid spread, typically a combination of low humidity, high temperatures, and strong winds. Red Flag Warnings trigger increased staffing at fire stations and pre-positioning of suppression resources. They do not mean a fire has started. They mean conditions are dangerous if one does.

Related: Wildfire, National Weather Service (NWS), NOAA Weather Radio

Regenerator (Stirling engine)

A heat store inside a Stirling engine that absorbs heat from the working gas as it moves toward the cold side and returns that heat as the gas travels back. It raises efficiency substantially, because heat that would otherwise be discarded is reused on every cycle. An engine without one still runs, but it wastes most of the heat it moves.

Related: Free-Piston (Stirling engine)

Registered Apprenticeship

A job-based training program registered with the U.S. Department of Labor or a state apprenticeship agency that combines structured on-the-job training with related classroom instruction. Apprentices are paid while they learn, with wages that rise as their skills grow, and finish with a portable, nationally recognized credential in their industry. Program length varies with the occupation and the employer.

Rekey (a Lock)

Changing the pins inside a lock cylinder so the old keys no longer work, while keeping the same lock hardware. It is usually cheaper than replacing the lock and is the standard step after keys are lost, stolen, or held by someone who should no longer have access.

Related: Strike Plate, Door Jamb

Renter's Insurance

An insurance policy that covers a renter's personal property, temporary living expenses if the unit becomes uninhabitable, and personal liability. The landlord's insurance covers the building structure but not a tenant's belongings or relocation costs. Typical policies cost $15 to $30 per month.

Related: Insurance Adjuster

Replacement Cost

What it costs today to replace an item with a new one of like kind and quality, without subtracting depreciation. Many policies pay actual cash value first and the remaining amount after you replace the item and send proof.

Related: Actual Cash Value (ACV), Deductible

Resilience

The capacity to withstand disruption and recover from hardship without permanent loss of function. Resilience applies at every scale, from a single household maintaining normalcy during a power outage to a community rebuilding after a flood. Physical preparedness, financial reserves, social networks, and mental fitness all contribute to resilience.

Related: Readiness, Fortitude, Sustainability

Resin Identification Code

A number inside a small triangle stamped on plastic items that identifies the type of plastic resin used. The triangle resembles a recycling symbol but does not mean the item is recyclable in your area. Whether a given resin code is accepted depends entirely on what your local recycling program can process and sell.

Related: Household Hazardous Waste (HHW)

Resourcefulness

The ability to solve problems with whatever is available rather than waiting for ideal conditions or supplies. Resourcefulness is a skill that improves with practice. Heritage-era households, working with far fewer commercial products, developed resourcefulness as a core survival trait.

Related: Capability, Fieldcraft, Resilience

Responsibility Matrix

A chart that lists a group's recurring jobs and names who is responsible for each one. Businesses commonly use a version called a RACI matrix (responsible, accountable, consulted, informed), and households can use a simpler form with an owner, helper, and backup for each job.

Related: Mental Load

Reverse Osmosis

A water filtration method that forces water under pressure through a semi-permeable membrane with pores small enough to block dissolved contaminants, including PFAS, arsenic, nitrates, fluoride, and lead. Reverse osmosis systems are certified to NSF/ANSI 58 and remove a broader range of chemical contaminants than carbon or gravity filters. They require electricity and produce waste water alongside purified water.

Related: PFAS (Per- and Polyfluoroalkyl Substances), NSF/ANSI Certification, Gravity Filter, Micron

Riparian Rights

The water law tradition followed in most eastern states, under which landowners along a watercourse hold a right to make reasonable use of the water so long as that use does not unreasonably harm other owners along the same water. The right attaches to the land and is not lost through non-use. Most eastern states now administer it through a permit system rather than leaving it to common law alone.

Related: Prior Appropriation, Instream Flow, Hydraulic Head

Rolling Blackout

An intentional, temporary shutdown of electricity to rotating sections of the grid to prevent a total system collapse when demand exceeds supply. Rolling blackouts typically last 15–60 minutes per area before power is restored and the blackout moves to the next zone. They are a last-resort measure that signals the grid is at or beyond its limits.

Related: Power Grid, Electric Reliability Council of Texas (ERCOT), Cascading Failure

Rotor Diameter

The diameter of the circle swept by a turbine's blades. It sets the swept area and therefore how much air the machine can work with, which makes it the most useful single size figure for comparing turbines. Doubling rotor diameter quadruples swept area.

Related: Betz Limit (Betz's Law), Hub Height, Nameplate Rating

Run-of-River

A hydroelectric arrangement that diverts part of a stream through a pipe to a turbine and returns it to the same stream a short distance downstream, without building a reservoir or flooding land. Most micro-hydro systems work this way and use only a fraction of available flow. The trade is that output follows the stream rather than household demand, since nothing is stored.

Related: Micro-Hydro, Penstock, Tailrace, Impoundment

Runaway Speed

The speed a turbine reaches when its electrical load disappears and nothing absorbs the energy still arriving. For an impulse water turbine it is roughly 1.8 times rated speed, reached within seconds, and it is treated as the worst-case mechanical load a machine will see. Because centrifugal stress rises with the square of speed, the forces on the rotating parts more than triple.

Related: Diversion Load, Water Hammer, Impulse Turbine

Running Watts

The power a device draws during normal operation, as opposed to its maximum or startup draw. This is the figure that matters for sizing backup power, and it is usually far below the number printed on the appliance. A refrigerator labelled 725 watts commonly runs at 100 to 200.

Related: Nameplate Rating, Startup Surge, Duty Cycle

Safe Minimum Internal Temperature

The lowest temperature, measured with a food thermometer, at which a food is safe to eat. It is 165°F for all poultry and leftovers, 160°F for ground meat, and 145°F with a 3-minute rest for whole cuts of beef, pork, and lamb.

Related: Danger Zone

Saffir-Simpson Hurricane Wind Scale

The 1–5 rating system used to classify hurricane intensity based on sustained wind speed, from Category 1 (74–95 mph, minimal damage) to Category 5 (157+ mph, catastrophic damage). The scale measures only wind. It does not account for storm surge, rainfall, or flooding, which often cause more damage and deaths than wind alone. A Category 1 hurricane with heavy rain can cause more flooding damage than a Category 4 with less rain.

Related: Hurricane, Storm Surge

SAM Splint

A lightweight, moldable splint made of a thin aluminum core covered in foam, used to support a suspected limb injury until medical care is available. A staple of outdoor first aid kits because it packs flat and shapes to any limb.

Related: First Aid, Trauma Shears

Substance Abuse and Mental Health Services Administration (SAMHSA)

The federal agency within HHS that leads public behavioral health efforts, including disaster mental health response. SAMHSA operates the Disaster Distress Helpline (1-800-985-5990), a 24/7 crisis counseling service for people experiencing emotional distress related to any natural or human-caused disaster. The helpline is free, multilingual, and confidential.

SBA Disaster Loan

A low-interest loan from the U.S. Small Business Administration available to homeowners, renters, businesses, and nonprofits after a declared disaster. Despite the name, SBA disaster loans are available to individuals, not just businesses. They cover property damage, personal property replacement, and economic injury. Loan amounts can reach $500,000 for real estate and $100,000 for personal property.

Related: Federal Emergency Management Agency (FEMA), Disaster Declaration, FEMA Individual Assistance (IA)

Section 608 Certification

An EPA certification required for anyone who services refrigerators, air conditioners and similar equipment in ways that could release refrigerant, such as attaching gauges or adding or removing refrigerant. Certification comes by equipment type, from Type I for small appliances through Universal, and does not expire.

Related: Heating, Ventilation, and Air Conditioning (HVAC)

Seebeck Effect

The generation of a voltage across a material when its two ends are held at different temperatures. It is the principle behind thermoelectric generators, which turn a temperature difference directly into direct current with no moving parts. The voltage depends on the size of that difference, so cooling the cold side matters as much as heating the hot side.

Seismic Retrofit

The modification of an existing building to make it more resistant to earthquake damage, typically by bolting the structure to its foundation, bracing cripple walls, and reinforcing connections between floors and walls. In earthquake-prone regions, seismic retrofits are among the most cost-effective preparedness investments a homeowner can make. Some jurisdictions offer incentive programs that cover a portion of retrofit costs.

Related: Earthquake, Building Code, Structural Assessment

Self-Sufficiency

The ability to meet your own essential needs without relying on outside support. Self-sufficiency exists on a spectrum, from maintaining a three-day water supply to growing a significant portion of your own food. Most households benefit from building toward greater self-sufficiency incrementally rather than attempting full independence overnight.

Related: Autonomy, Independence, Sustainability

Setback (Zoning)

In zoning, the minimum distance a structure must stand from a property line, road, or dwelling. Wind ordinances commonly express turbine setbacks as a multiple of total tower height, which can make a legal tower impossible on a small lot even where the use itself is permitted.

Related: Guyed Tower, Hub Height

Shelf Life

The length of time a food product remains safe and nutritionally adequate when stored under recommended conditions. 'Best by' and 'use by' dates on most shelf-stable foods are quality indicators, not safety cutoffs, and many products remain safe well past those dates. The exception is infant formula, which has a federally regulated use-by date tied to nutrient degradation.

Related: FIFO (First In, First Out), Food Storage, Pantry Discipline

Shelf-Stable Food

Food that can be safely stored at room temperature in a sealed container for an extended period without refrigeration. Examples include canned goods, dried pasta, rice, peanut butter, crackers, granola bars, and dried fruit. Shelf-stable foods are the foundation of apartment emergency food storage because they require no refrigeration and minimal preparation.

Related: Shelf Life, Food Storage

Shelter in Place

An emergency instruction to remain inside your current building and seal it against an external hazard, typically a chemical release, severe weather, or active threat. Sheltering in place is distinct from evacuation; it means staying put, closing windows and doors, and in chemical events, sealing gaps with plastic and tape. The decision to shelter vs. evacuate depends on the specific hazard.

Related: Evacuation Order, 72-Hour Bag, NOAA Weather Radio

Situational Awareness

Understanding your environment, recognizing what is normal, and noticing when conditions change. In preparedness, situational awareness means knowing the hazards in your region, understanding the systems your household depends on, and maintaining enough attention to recognize when something shifts. It is a trainable skill, not an innate trait.

Related: Vigilance, Foresight, Operational Readiness

SKYWARN

A National Weather Service program that trains volunteer weather spotters to identify and report severe weather conditions (tornadoes, large hail, damaging winds, and flash flooding) to their local NWS forecast office. SKYWARN training is free, typically 2–3 hours, and available through local NWS offices. Spotter reports are a critical data source for NWS forecasters issuing warnings.

Related: National Weather Service (NWS), NOAA Weather Radio, Community Emergency Response Team (CERT)

Smart Meter

A digital electric or gas meter that records usage in short intervals and transmits the data to the utility without a meter reader. Smart meters let a household see usage by hour or day, which makes it possible to build an energy-use baseline and spot waste. Most U.S. electric utilities have deployed them to the majority of their customers.

Related: Kilowatt-hour (kWh), Time-of-Use Pricing (TOU)

Smoke Alarm

A device that detects smoke particles in the air and sounds an audible alarm to warn occupants of a potential fire. NFPA 72 requires smoke alarms inside every sleeping room, outside each sleeping area, and on every level of a home. Working smoke alarms reduce the risk of dying in a home fire by roughly 50 percent.

Related: Carbon Monoxide (CO), NFPA 72 (National Fire Alarm and Signaling Code)

Smoke Point

The temperature at which a cooking oil or fat starts to break down and give off a steady stream of visible smoke. Oil heated past it develops harsh flavors, so high-heat jobs like searing and seasoning cast iron call for an oil with a high smoke point. Refined oils generally have higher smoke points than unrefined ones.

Supplemental Nutrition Assistance Program (SNAP)

The federal program that provides nutrition assistance to low-income individuals and families through an electronic benefits transfer (EBT) card usable at authorized retailers. SNAP benefits are calculated based on the USDA Thrifty Food Plan, the minimum-cost nutritionally adequate diet. After a presidential disaster declaration, D-SNAP (Disaster SNAP) can provide temporary food benefits to disaster-affected households that don't normally qualify.

Related: Thrifty Food Plan, Hazel Stiebeling, Federal Emergency Management Agency (FEMA)

Social Capital

The networks of relationships among people in a community that enable cooperation, trust, and collective action. In disaster research, social capital is the single strongest predictor of both survival and recovery, stronger than income, infrastructure quality, or government response speed. Neighborhoods where residents know each other by name evacuate faster, share resources more effectively, and rebuild more completely.

Related: Mutual Aid, Communication Tree, Block Captain

Solar Panel

A device that converts sunlight into electricity using photovoltaic cells. For household preparedness, solar panels paired with battery storage provide backup power that does not depend on fuel or the grid. A basic portable solar setup (200W panel + battery station) can keep phones charged, run LED lights, and power a small refrigerator during a multi-day outage.

Related: Generator Interlock, Power Grid

Solid-Core Door

A door whose interior is filled with wood, composite, or another dense material instead of the cardboard honeycomb inside a hollow-core door. A solid-core or metal exterior door resists kicking and prying far better than a hollow-core one, which makes it the foundation for any lock upgrade. Hollow-core doors are generally made for interior use.

Related: Strike Plate

Spillway

The controlled route by which a dam passes water it cannot hold. Its capacity is sized against an inflow design flood rather than against ordinary experience, and inadequate capacity is among the leading causes of dam failure. A spillway partly blocked by debris is a smaller spillway, and the blockage tends to arrive with the storm that needs full capacity.

Related: Impoundment, Hazard Potential Classification

Split-Phase Service

The standard residential electrical supply in North America, delivering both 120 volts and 240 volts from the same service. Large appliances such as ranges, dryers, and well pumps use the 240-volt side, which portable power stations cannot produce at any capacity. This is why a 240-volt device cannot run from a battery station regardless of size.

Related: Generator Interlock, Continuous Output

Startup Surge

The brief spike in power a motor or compressor draws in the moment it starts. Surge is a pass-or-fail limit rather than something a safety margin absorbs, so a station can hold ample energy and still fail to start a refrigerator. Sealed compressors commonly draw three to five times running watts for a second or two.

Related: Locked-Rotor Amps (LRA), Running Watts, Continuous Output

Steel Burr Mill

A grain mill that crushes grain between steel plates or cones turning at slow speed. It covers cracked grain through fine flour, and unlike stone and impact mills, some steel burr models can grind wet, oily, or fibrous material. Many hand-crank grain mills use steel burrs.

Related: Stone Burr Mill, Impact Mill

Stoicism

A philosophical tradition emphasizing emotional self-regulation, focus on what you can control, and endurance through difficulty. In a preparedness context, stoic principles apply directly: control your response rather than the situation, prepare for what is likely rather than fear what is possible, and maintain composure so those around you can function.

Related: Fortitude, Discipline, Agency

Stone Burr Mill

A grain mill that grinds between two flat abrasive stones, one turning against the other, with the gap between them setting the texture. Stone burr mills make everything from fine flour to cereal and cracked grain, but they are not suited to wet or oily material. Both electric and hand-crank models are sold.

Related: Impact Mill, Steel Burr Mill

Stop Point

A predetermined inventory level at which a household considers its stored supplies sufficient and stops adding supplies. Setting a stop point prevents open-ended buying driven by anxiety rather than need. A common starting stop point is two weeks of food, water, and essential medications for every person in the household.

Related: Food Storage, Shelf Life

Storm Sewer

A drainage system that carries rainwater and surface runoff directly to a local waterway without treatment. A storm sewer is not connected to the sanitary sewer that handles household wastewater, so anything poured into a storm drain reaches a stream, lake, or river untreated.

Related: Household Hazardous Waste (HHW)

Storm Surge

An abnormal rise in sea level generated by a storm's winds pushing ocean water onshore. Storm surge is the deadliest hazard associated with hurricanes, responsible for more fatalities than wind in most major events. Surge heights can exceed 20 feet in extreme storms.

Related: Hurricane, Evacuation Order, Flood

Structural Assessment

A professional evaluation of a building's structural integrity after a disaster, determining whether the structure is safe to enter, safe to occupy, or requires demolition. Structural assessments should be performed by a licensed structural engineer, not a general contractor. A typical post-disaster residential assessment costs $300–$600.

Related: Mold Remediation, Building Code

Supercell

A severe thunderstorm characterized by a deep, persistent rotating updraft called a mesocyclone. Supercells are the most dangerous type of thunderstorm and are responsible for nearly all significant tornadoes, as well as very large hail, damaging winds, and flash flooding. They can persist for hours and travel hundreds of miles.

Related: Tornado, Enhanced Fujita (EF) Scale

Supply and Delivery Charges

The two main components of a deregulated electric bill. The supply charge covers the cost of generating the electricity and is often shoppable in deregulated states. The delivery charge covers the wires, poles, meters, and maintenance that bring electricity to the home, and is set by the local utility regardless of who supplies the power.

Related: Kilowatt-hour (kWh), Time-of-Use Pricing (TOU)

Sustainability

Maintaining long-term viability with limited or finite resources. In preparedness, sustainability means building systems that can function over weeks and months, not just the first 72 hours. A garden that produces food year after year is more sustainable than a stored supply that runs out. Sustainable preparedness plans account for resupply, rotation, and maintenance.

Related: Self-Sufficiency, Resilience, Prudence

Syngas (Synthesis Gas)

A fuel gas made up mainly of carbon monoxide and hydrogen, produced by gasifying a solid fuel such as wood or coal. The name is used loosely: in industry it means a gas made for chemical synthesis, while in small-scale wood gasification it is often used interchangeably with producer gas. Both carry carbon monoxide at concentrations that are dangerous to breathe.

Related: Producer Gas

Strike Plate

The metal plate set into a door jamb where a latch or deadbolt slides in. It guides the bolt and protects the wood around the bolt hole. Builder-grade strike plates are often held by short screws that reach only the jamb, which is why replacing them with longer screws into the framing is one of the least expensive security upgrades for a door.

Related: Door Jamb, Mortise

Tailrace

The channel returning water to a stream after it has passed through a turbine. Its outlet needs protection from erosion, because water leaving a machine still carries energy, and in cold climates an iced tailrace can back water up into the powerhouse.

Related: Run-of-River, Penstock, Forebay

Tar Cracking

Breaking the heavy condensable compounds in gasifier gas into lighter permanent gases by passing them through a high temperature zone and a bed of glowing char. Without it those tars condense in pipework, filters and engine valves, which is the most common reason small gasifiers stop working. Cleaning the gas well also removes the tar smell that would otherwise give some warning of a leak.

Related: Producer Gas

TDS (Total Dissolved Solids)

A measure of the combined concentration of all inorganic and organic substances dissolved in water, expressed in milligrams per liter or parts per million. TDS includes minerals like calcium and magnesium (which are harmless or beneficial), as well as contaminants like nitrates and heavy metals. A high TDS reading does not indicate unsafe water; a low reading does not confirm safety.

Related: Reverse Osmosis, Turbidity

Telehealth

Health care delivered without a trip to the provider's office. It can be a video or phone visit, secure messages through a patient portal, or a device that shares readings such as blood pressure with your provider.

Tenancy in Common

A form of shared ownership in which each owner holds a fractional, undivided interest in the whole property. Every co-owner has an equal right to use all of it and shares responsibility for costs such as taxes, whatever the size of their share. Heirs' property is usually held this way.

Related: Heirs' Property, Partition Action

Tier II Inventory

The annual report a facility files under federal right-to-know law listing the hazardous chemicals it stored above reporting thresholds, in what quantity ranges, and where on site. Residents can request a specific facility's report through their state or their LEPC.

Related: Local Emergency Planning Committee (LEPC)

Total Harmonic Distortion (THD)

A measurement of how much a generator's electrical output deviates from a pure, smooth sine wave. Lower THD means cleaner power that is safer for laptops, phones, and medical devices, since a distorted waveform can damage sensitive electronics over time. Inverter generators typically hold THD under 3%, while conventional generators can run well above 10%.

Related: Inverter, Running Watts

Therm

A unit of heat energy equal to 100,000 BTU, commonly used on natural gas bills to measure how much gas a household consumed. One therm is roughly the energy in 100 cubic feet of natural gas, though the exact conversion depends on the gas quality in your area.

Related: Kilowatt-hour (kWh)

Thermal Baseload

The amount of heat a building or process needs continuously across the year, as distinct from the peak it needs on the coldest day. It is the figure combined heat and power equipment should be sized against, because a machine sized to peak heating demand has nowhere to send its heat for most of the year. Domestic hot water is often the only genuine thermal baseload a house has in summer.

Thermal Shock

Stress inside a material when one part heats or cools much faster than another. In cookware it can crack cast iron or damage enamel, which is why Lodge advises preheating iron slowly.

Related: Cast Iron Seasoning, Induction Cooktop

Thrifty Food Plan

The USDA's estimate of the minimum cost of a nutritionally adequate diet, used as the basis for calculating SNAP (food stamp) benefits. The Thrifty Food Plan is a direct descendant of Hazel Stiebeling's 1936 four-tier dietary framework. It is updated periodically, and the most recent revision in 2021 increased the estimated cost by roughly 20%.

Related: Hazel Stiebeling, Supplemental Nutrition Assistance Program (SNAP), Bureau of Home Economics

Time-of-Use Pricing (TOU)

A utility rate structure that charges different prices per kilowatt-hour depending on the time of day. Electricity typically costs more during afternoon and evening peak hours when demand is highest and less during overnight off-peak hours. Understanding the rate schedule lets a household shift discretionary loads like laundry, dishwashing, or EV charging to cheaper periods.

Related: Kilowatt-hour (kWh), Smart Meter

Tornado

A violently rotating column of air extending from a thunderstorm to the ground. Tornadoes can produce winds exceeding 300 mph and destroy well-built structures in seconds. The U.S. experiences roughly 1,200 tornadoes per year, more than any other country.

Related: Supercell, Enhanced Fujita (EF) Scale, Tornado Watch, Tornado Warning

Tornado Family

A series of tornadoes produced in sequence by the same parent thunderstorm, often leaving a long, broken damage path across a wide area. Before Doppler radar and organized damage surveys, a tornado family was frequently recorded in the historical record as a single continuous tornado, which inflated reported path lengths for older events.

Related: Supercell, Tornado Outbreak, Fujita Scale

Tornado Outbreak

Multiple tornadoes produced by the same weather system over a period of hours to days, often across several states. Outbreaks concentrate damage and casualties across a wide region at once, which can overwhelm local hospitals, shelters, and emergency responders who would otherwise handle a single tornado without strain.

Related: Tornado Family, Supercell, Disaster Declaration

Tornado Warning

An alert issued by the National Weather Service when a tornado has been sighted or indicated by radar, meaning a tornado is happening or imminent and people in its path should take shelter immediately. A tornado warning is more urgent than a tornado watch, which means conditions favor tornado formation but none has been confirmed yet.

Related: Tornado Watch, Wireless Emergency Alert (WEA), NOAA Weather Radio

Tornado Watch

An alert issued by the National Weather Service when conditions in an area are favorable for tornadoes to form, typically covering several hours and a large region such as a group of counties or an entire state. A tornado watch means stay alert and be ready to act, not that a tornado has been spotted. It is less urgent than a tornado warning.

Related: Tornado Warning, Wireless Emergency Alert (WEA), NOAA Weather Radio

Torpedo Level

A short spirit level, usually six to ten inches long, sized to fit a tool pouch and to work in the tight spaces where a full-length level will not sit. Most carry three vials reading level, plumb, and forty-five degrees. Check any level by reading a surface, turning the level end for end, and reading it again. The two readings should agree.

Trash Rack

A coarse screen at a water intake that stops branches, leaves and gravel from entering the system. It handles large debris, leaving finer material to a screen further along. Any screen fine enough to stop pine needles is fine enough to clog with them, which makes cleaning access a design question rather than an afterthought.

Related: Coanda Screen, Forebay, Weir

Trauma Shears

Blunt-tipped scissors with an angled blade designed to cut clothing, seat belts, and bandage material quickly without cutting the person underneath. A standard upgrade over the small scissors included in most prebuilt first aid kits.

Related: First Aid

Tsunami

A series of ocean waves generated by a large-scale disturbance, usually an undersea earthquake, volcanic eruption, or submarine landslide. Tsunami waves can travel across entire ocean basins at jet speed and arrive at coastlines with devastating force. The Pacific Northwest and Alaska are the U.S. regions with the highest tsunami risk, though the Atlantic and Gulf coasts have historical exposure.

Related: Earthquake, Evacuation Order

Turbidity

A measure of water cloudiness caused by suspended particles such as sediment, algae, or other matter that scatters light passing through the water. High turbidity can interfere with chemical disinfection by shielding pathogens from UV light or chlorine contact. Turbid water should be pre-filtered or allowed to settle before chemical treatment.

Related: Potable, Hollow Fiber Membrane, Backflush

Turbulence

Rapid, irregular variation in wind speed and direction, usually caused by buildings, trees, or terrain upwind of the rotor. Turbulent air both reduces output and increases fatigue loading on the machine. A sheltered yard can show usable wind on a regional map and unusable wind at the rotor.

Related: Wind Shear, Hub Height, Power Curve

Two-Step Verification

A security method that requires two separate forms of proof to log in, typically your password plus a code from your phone or an authenticator app. If an attacker obtains your password, they still cannot access your account without the second factor.

Related: Passkey, Password Manager, Phishing

UL (Underwriters Laboratories)

A global safety science organization that tests and certifies products, materials, and systems for safety. The UL Fire Safety Research Institute conducts fire behavior research, including studies on the life-safety benefits of closed doors and modern furnishing fire dynamics.

Related: Smoke Alarm, Fire Extinguisher (ABC-Rated)

U.S. Fire Administration (USFA)

A component of FEMA that provides fire data, research, public education, and training to reduce fire deaths, injuries, and property losses. USFA publishes guidance on home fire escape planning, high-rise fire safety, and fire prevention for residential buildings.

Related: Federal Emergency Management Agency (FEMA)

U.S. Geological Survey (USGS)

The federal science agency responsible for studying the nation's landscape, natural resources, and natural hazards, including earthquakes, volcanoes, landslides, and wildfire. USGS operates the earthquake monitoring network, produces wildfire risk maps, and maintains stream gauges that feed flood forecasting models. USGS data is the foundation of most natural hazard risk assessments in the United States.

Related: Earthquake, Wildfire, National Oceanic and Atmospheric Administration (NOAA)

U.S. Weather Bureau

The federal weather agency that operated from 1890 to 1970, the predecessor of today's National Weather Service. For decades it discouraged the word tornado in public forecasts out of concern that warnings would cause panic, and it did not begin issuing public tornado warnings until 1952. It became the National Weather Service when NOAA was created in 1970.

Related: National Weather Service (NWS), Tornado Warning

Uniform Partition of Heirs Property Act (UPHPA)

A model law from the Uniform Law Commission that changes how courts handle partition cases involving heirs' property. It adds notice to all heirs, a fair-value appraisal, and a right for the other co-owners to buy out the one who filed, and when a sale is ordered it is usually on the open market. As of the end of 2025 it had been enacted in 24 states, the District of Columbia, and the U.S. Virgin Islands.

Related: Heirs' Property, Partition Action

Vector

An organism that transmits a pathogen from one host to another. In household pest management, common vectors include mosquitoes (which can carry West Nile virus and other diseases) and ticks (which can carry Lyme disease and other tick-borne illnesses). Rodents can also serve as vectors for hantavirus and other pathogens.

Related: Integrated Pest Management

Vigilance

Sustained, calm attention to conditions that could affect household safety or stability. Vigilance is not anxiety. It is the practiced habit of monitoring weather alerts, checking supplies on a schedule, maintaining equipment, and staying informed through reliable sources without letting the monitoring itself become a source of stress.

Related: Situational Awareness, Foresight, Discipline

Voice Cloning

The use of AI to replicate a specific person's voice from a short sample of their speech. Cloned voices are used in scams where the caller impersonates a family member, bank representative, or government official. A family code word and the callback habit are the primary household defenses.

Related: Deepfake

Voltage Drop

The loss of voltage along a conductor caused by its own resistance, which grows with current and with the length of the run. A long run between array and controller can waste a real share of what the panels produce, and the fix is thicker conductor rather than more panels. Design targets are commonly held to a few percent of system voltage.

Related: Open-Circuit Voltage (Voc), Solar Panel

Vulnerability Mapping

The process of identifying which households on a block have members who may need additional help during an emergency: people who live alone, have mobility limitations, depend on medical equipment, have young children, or don't speak English. Vulnerability maps are sensitive documents that should be maintained on paper by 2–3 trusted block coordinators and updated annually. The goal is to ensure no one is forgotten during an evacuation or outage.

Related: Block Captain, Map Your Neighborhood (MYN), Communication Tree

Water Hammer

The pressure surge produced when moving water is stopped or slowed quickly, as when a valve closes fast. The rise equals the speed of the pressure wave in the pipe multiplied by the change in water velocity, divided by gravity, which means a modest system can briefly see several times its normal pressure. It is a common cause of burst pipe in both household plumbing and hydroelectric penstocks.

Related: Penstock, Hydraulic Head, Runaway Speed

Water Preserver Concentrate

A commercial sodium hypochlorite additive formulated to maintain a protective chlorine residual in stored water for up to five years when added at the manufacturer's specified dose at fill time. It addresses the natural dissipation of chlorine residual that occurs in tap water stored in sealed containers over months. One package typically treats up to 55 gallons and costs $10 to $15.

Related: Potable, HDPE (High-Density Polyethylene)

Water-Bath Canning

A home preservation method in which sealed jars of high-acid food (fruits, pickles, jams, tomatoes with added acid) are processed in boiling water (212°F) for a specified time. Water-bath canning is safe only for high-acid foods (pH 4.6 or below); low-acid foods require pressure canning. The method has been used in American households since the 19th century and is documented extensively in USDA bulletins.

Related: Pressure Canner, National Center for Home Food Preservation (NCHFP)

Water Main

A large underground pipe that carries treated drinking water from a distribution hub to neighborhoods and buildings. Water mains in the U.S. range in age from new installations to cast-iron pipes over 100 years old. The American Society of Civil Engineers estimates there are approximately 240,000 water main breaks per year in the U.S., resulting in the loss of roughly 6 billion gallons of treated water daily.

Related: Distribution System, Boil Water Advisory

Water Storage

The practice of maintaining a supply of clean drinking water for use during disruptions to the municipal water system. The standard recommendation is one gallon per person per day for at least three days, covering drinking, cooking, and basic hygiene. Stored water should be replaced every six months if using tap water, or stored in commercially sealed containers with longer shelf lives.

Related: Boil Water Advisory

Waterwheel

A wheel turned by falling or flowing water, the oldest hydropower machine and still a practical one at very low head. Measured hydraulic efficiency of well-designed wheels reaches 75 to 85 percent, better than their reputation suggests. Their real limitation is rotational speed, since a large wheel turns at around ten revolutions per minute and driving a generator from that requires heavy gearing.

Related: Overshot Wheel, Micro-Hydro, Hydraulic Head

Watt-hour (Wh)

A unit of energy equal to one watt drawn for one hour. It measures the total energy a battery holds or a device consumes over time, which is the figure that decides whether a power station lasts the night. A full-size refrigerator uses roughly 1,000 to 2,000 watt-hours per day.

Related: Running Watts, Continuous Output, Duty Cycle

Wireless Emergency Alert (WEA)

A public safety system that pushes short emergency alerts directly to cell phones in a targeted geographic area without requiring a subscription or app. WEA messages include AMBER alerts, severe weather warnings, and presidential alerts. WEA depends on cell tower coverage. If towers are down or the area lacks coverage, the alert will not reach phones in that zone.

Related: NOAA Weather Radio, Evacuation Order, Emergency Alert System (EAS)

Weir

A barrier placed across a channel with a notch of known shape cut into it, so that the depth of water flowing over the notch corresponds to a calculable flow rate. Weirs are used to measure stream discharge repeatedly over a season, and low weirs also serve to raise water slightly at an intake without impounding any meaningful volume behind them.

Related: Cubic Feet per Second, Trash Rack, Forebay

Wildfire

An unplanned fire burning in natural vegetation: forests, grasslands, or brush. Wildfires can be ignited by lightning or human activity and may spread across thousands of acres when conditions align. The U.S. averages roughly 70,000 wildfires per year.

Related: Wildland-Urban Interface (WUI), Defensible Space, Prescribed Burn, Fire Behavior Triangle

Wind Shear

The increase in wind speed with height above ground. It is described by a power law whose exponent stands in for how rough the surrounding ground is, and it is why tower height affects annual production so strongly. Distributed wind site work commonly applies a shear exponent of 0.14.

Related: Hub Height, Turbulence, Anemometer

Winter Storm

A weather event bringing heavy snow, ice, freezing rain, or extreme cold over a wide area. Winter storms can collapse power grids, make roads impassable, and isolate households for days. Ice storms are particularly damaging to power infrastructure because ice accumulation on lines and trees causes widespread outages.

Related: Generator Interlock, Rolling Blackout

Works Progress Administration (WPA)

A New Deal agency (1935–1943) that employed millions of Americans on public works projects during the Great Depression, including construction, arts, and writing. The WPA's Federal Writers' Project produced the 'America Eats' manuscripts documenting regional foodways and roughly 2,900 life-history interviews with ordinary Americans, both now invaluable primary sources for understanding Depression-era household economics.

Related: Federal Writers' Project, Bureau of Home Economics, America Eats (WPA)

Wildland-Urban Interface (WUI)

The zone where developed land (houses, businesses, infrastructure) meets or intermingles with undeveloped wildland vegetation. Homes in the WUI face elevated wildfire risk because fire can move directly from wildland fuels to residential structures. As of 2020, the WUI contains roughly 44 million U.S. homes, 32% of all housing.

Related: Defensible Space, Wildfire, Fire-Adapted Community

Yaw

Rotation of a turbine about its vertical axis so the rotor faces into the wind. Small machines usually yaw passively with a tail vane, while larger ones use a powered drive.

Related: Furling, Pitch Control, Overspeed

Zoning

Municipal regulations that divide land into districts and specify what activities, structures, and uses are permitted in each. Zoning determines whether a property can host livestock, outbuildings, home-based businesses, or agricultural activity. Rural, agricultural, and mixed-use zones generally allow the widest range of self-reliance activities.

Related: Homeowners Association (HOA), Setback (Zoning)