What to do when volcanic ash is falling

Volcanic ash is nothing like ash from a fire. It is not light, it is not soft and it does not go away on its own. It is tiny fragments of rock and ground glass, hard and sharp-edged, and that physical difference explains almost everything you need to do about it.

While it falls: staying inside is the measure

The most effective protection against ash is not something you buy: it is not being underneath it.

• Close doors and windows and lay damp cloths along any gap letting dust through.
• Turn off forced ventilation, air conditioning and extractor fans. They pull ash in and clog.
• Bring pets inside. Wash paws and coats afterwards; they walk through ash and then groom themselves.
• Cover what scratches: electronics, glass, exposed motors.

If you must go out, wear an N95 and sealed goggles, long sleeves, and shake off outside before coming in. Anyone using contact lenses should switch to ordinary glasses: ash trapped between lens and eye scratches the cornea.

The roof: it weighs more than it looks

The structural risk from ash arrives with water. Dry ash is already heavy; wet ash can weigh twice as much, and that is when roofs give way.

The practical rule is simple: ash comes off before it rains, not after. If rain is forecast and ash has built up, that is the day’s priority.

When clearing it:

• Work dry or lightly dampened, never flooded. Pressure washing turns ash into a paste that blocks downspouts and drains.
• Do not put it down the drain or the toilet. It sets and blocks the plumbing.
• Bag it and check with local authorities where to take it; there are usually designated points.
• Share the work. Clearing a roof is heavy physical effort while wearing a respirator, and eruption zones have recorded cardiac events from overexertion during clean-up.

The car: filters and windshield

Part	What happens	What to do
Windshield	Scratches permanently	Rinse with plenty of water before wiping anything
Engine air filter	Saturates within a few miles	Carry a spare and check it often
Brakes and transmission	Ash acts as an abrasive	Drive slowly and inspect afterwards
Paint	Marks when rubbed dry	Rinse, never drag a dry cloth

Once it stops

Settled ash lifts again with wind and with every passing vehicle, so respiratory precautions still apply days or weeks after the plume is gone. Anyone with asthma, COPD or a heart condition should keep wearing a respirator outdoors while dust remains in the air.

If you live near a USGS-monitored volcano, the ZonaProtec monitor shows its current alert level alongside the rest of the hazards near you.