How many active volcanoes are in the United States?

There are 161 potentially active volcanoes in the United States, according to Ready.gov. Alaska, Hawaii, California, Washington, and Oregon have the largest concentrations, though other states and territories also have active volcanoes.

How far can volcanic ash travel?

Volcanic ash can travel hundreds of miles from the eruption site, carried by wind. Communities far from a volcano can still experience ashfall, contaminated water, reduced visibility, and respiratory irritation.

Is it safe to shelter indoors during heavy ashfall?

Only for a few hours. If ash keeps falling continuously, the weight of accumulating ash can collapse a roof and block air intakes. Local authorities may advise evacuating if ashfall is expected to continue.

What mask actually protects against volcanic ash?

A NIOSH approved N95 respirator, fitted snugly to the face, filters the fine ash particles that reach deep into the lungs. A nuisance dust mask offers some comfort but far less protection, and should only be used as a last resort for short periods outdoors.

How do I safely clear ash from my roof?

Wear an N95 respirator and protective clothing, and move carefully since wet ash is slippery. Ash is heavy enough to overload and collapse a roof, so clear it in manageable sections rather than waiting for it to build up, and avoid the work entirely if you are not confident on a roof.

Volcanic Eruption Checklist — Before, During & After Ashfall

Phase 1

Before an eruption. Know your risk and your routes.

Volcanic activity often builds over days or weeks, but ashfall and evacuation orders can still move faster than expected. Households near an active volcano benefit most from preparing early.

Home Protection

Stage ash protection supplies: goggles, long sleeves, and material to seal vents, doors, and windows

Medical

Keep a supply of N95 respirators and learn to fit them. Cloth masks do not filter fine ash particles

Evacuation

Pack a 72-hour bag for each person in your household: medication, a change of clothes, document copies, water, and a phone charger
Identify your household meeting point and one out-of-area contact
Map two evacuation routes out of your area and drive them before you need them

Water

Store 1 gallon per person per day for at least 3 days, including pets

Food

Build a 3-day supply of shelf-stable food per person that needs no cooking

Power and Lighting

Get LED lanterns or flashlights for every main room
Get a power bank for each phone in your household

Communications

Turn on Wireless Emergency Alerts and sign up for the USGS Volcano Notification Service
Get a battery-powered or hand-crank NOAA weather radio for when cell service fails

Documents

Get a waterproof, fireproof container for document copies, plus password-protected digital backups

Phase 2

During an eruption. Follow local guidance, seal your space.

What you do during an eruption depends heavily on where you are relative to the volcano. Lava, lahars, and pyroclastic flows call for immediate evacuation. Ashfall alone often calls for shelter in place.

If You Must Evacuate

Leave the area immediately if lava, a lahar, or a pyroclastic flow is headed toward you
Avoid areas downwind of the volcano and river valleys downstream, ash and rubble follow wind and gravity
Expect heavy traffic and delays. Follow designated evacuation routes since others may be blocked

If You Shelter in Place

Close windows, doors, and fireplace dampers, and turn off heating, cooling, and fans to keep ash and gases out
Move to an interior room without windows, and keep listening to your radio until told it is safe or told to evacuate
Avoid driving in heavy ash. If you must drive, keep windows up and the air conditioning off
If ashfall continues for more than a few hours, listen for evacuation guidance. Continuous ash accumulation can overload a roof

Phase 3

After an eruption. Ash cleanup has its own hazards.

Volcanic ash is heavier and more abrasive than it looks. Most post-eruption injuries come from roof collapses, falls during cleanup, and breathing unprotected ash, not from the eruption itself.

Immediate Safety

Stay indoors until local authorities confirm it is safe to go outside
Listen to local updates on air quality, drinking water, and road conditions before resuming normal activity
Wear an N95 respirator outdoors and while cleaning ash that has gotten inside
Keep anyone with asthma or a lung condition away from ash exposure until air quality clears

Cleanup and Documentation

Photograph ash and property damage before cleanup for your insurance claim
Clear roof ash carefully and in sections. Ash is heavy enough to collapse a roof and slippery enough to cause falls
Keep children away from cleanup work, and replace or clean furnace filters frequently afterward
Check on elderly neighbors and anyone with respiratory conditions

Gear

Still need to get equipped? Start here.

A few items do most of the work in a volcanic eruption. These are the ones worth having before ash is ever in the forecast.

Browse all gear reviews →

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Volcanic Eruption Checklist. Before, during, and after.