Volcanic ash and the house

Volcanic ash is fine, sharp grit, small enough to get into all but the most tightly sealed buildings and to be breathed deep into the lungs. An ashfall rarely threatens life directly. The bigger dangers are a roof collapsing under heavy ash, and accidents during cleanup and on the road. Ash also irritates the eyes and airways, most of all for people with asthma or other lung conditions. Ash can also cut power and close roads for days. Building an emergency kit and keeping it current covers the supplies.

Before an eruption

Sign up for the Volcano Notification Service, which sends free alerts about volcanic activity. Ask your local emergency management office about evacuation and shelter plans for your area. Keep food, water and cleaning supplies for several days, with medicine for each person and for your pets. If anyone in the house has a lung or breathing condition, talk to their doctor ahead of time.

When ash is falling

• Follow evacuation ordersIf you're told to leave, leave early. Stay away from areas downwind and from river valleys downstream of the volcano.
• Seal the houseShut the doors and windows and cover vent openings. Turn off heat pumps and air conditioners that draw in outside air.
• Cover the carPark it under cover or put a tarp over it.
• Keep ash out of rain barrelsDisconnect downspouts from any tank that collects roof water.
• Stay insideWait until officials say it's safe. If you must go out, wear a well-fitting N95 mask and goggles, and wear glasses rather than contact lenses.
• Keep medicine closePeople with asthma or a heart condition should keep their inhalers and medicine on hand.
• Text rather than callPhone lines are often busy, so save calls for emergencies.

The roof and the gutters

Stay off the roof. Ash makes it slippery, and a heavy load can bring it close to collapse. Wet ash can weigh up to twice as much as dry ash. Very thick deposits, over about 4 inches and more often over a foot, can collapse a roof, and long, low-pitched roofs are the most at risk. Ash also clogs gutters and downspouts, which adds weight and sends water where it shouldn't go. Have a roofer clear the roof and gutters, and don't add your own weight to an overloaded roof.

Cleaning up inside

• Vacuum carpets, furniture and appliances first. A vacuum with a HEPA filter works best, and empty it carefully so the ash doesn't blow back out.
• Don't dry-sweep or blow ash around with compressed air.
• Wipe small surfaces and floors with a damp cloth.
• Dab glass, porcelain and acrylic with a sponge soaked in detergent rather than wiping, so the grit doesn't scratch.
• Rinse ash-coated fabrics under running water before washing them in small loads with extra detergent. Make sure they're free of ash before they go in the dryer.
• Clean the refrigerator's air intake and the stove fan and vents.

For several months after an ashfall, furnace and air conditioner filters can clog quickly, so check them and change them often. How to change a furnace filter walks through it. Wear a mask and protective clothing while you clean, and keep children out of the cleanup.

Water and the garden

If ash gets into stored water, let it settle and use the clear water on top. Ash usually makes water taste bad before it makes it unsafe. Vegetables from the garden can be eaten once they're washed.

An annotated example

What to do next

Sign up for the Volcano Notification Service if you live near an active volcano, and add N95 masks and goggles to your emergency kit. After an ashfall, have a roofer clear the roof and gutters, and change the furnace and air conditioner filters often for the next several months.