Volcano Safety Guide: How to Prepare for an Eruption

Before an eruption: preparation that saves lives

If you live near or are traveling to an active volcano, preparation begins long before any sign of activity. The single most important step is knowing your hazard zone.

• Learn your local hazard map. National observatories publish maps showing which valleys carry lahars and which zones face pyroclastic flows. Know whether you are in one.
• Identify two evacuation routes that head to high ground, away from river valleys and downslope drainages.
• Agree on a family meeting point and an out-of-area contact, since local phone lines often fail.
• Sign up for official alerts from your national volcano observatory or emergency agency.

Understanding which eruption style your local volcano produces helps you anticipate the threat — review the types of eruptions for your region.

Your volcano emergency kit

Keep a grab-and-go kit ready. Volcanic emergencies add a few items beyond a standard disaster kit, chiefly for protection against ash:

• N95 (or better) respirator masks for every family member — ordinary cloth masks do not filter fine ash.
• Sealed goggles to protect eyes from abrasive ash (not regular glasses).
• Drinking water — at least 3 liters per person per day for several days; ash contaminates open supplies.
• Non-perishable food, a manual can opener, and any essential medications.
• Battery or hand-crank radio to receive alerts if the power and internet fail.
• Flashlight, first-aid kit, sturdy shoes, and work gloves.
• Important documents (ID, insurance) in a waterproof bag.

Understanding volcano alert levels

Most observatories use a tiered alert system. The U.S. Geological Survey uses a four-level scheme that is broadly typical worldwide:

The golden rule is simple: if authorities order an evacuation, leave at once. The 1991 Pinatubo evacuation saved thousands of lives precisely because people left before the eruption. The Armero tragedy of 1985 happened because warnings went unheeded.

Surviving ash fall

Volcanic ash affects the largest area and the most people. If ash is falling and you have not been told to evacuate, the safest action is usually to shelter indoors:

• Go inside and close all windows, doors, and vents. Place damp towels at door gaps.
• Wear your N95 mask and goggles if you must go outside.
• Do not drive unless necessary — ash reduces visibility, makes roads slippery, and clogs engines.
• Clear ash from your roof if it accumulates beyond a few centimeters, but only safely — wet ash is heavy and can collapse roofs. Watch your footing.
• Protect electronics and water — cover machinery and keep stored water sealed.
• People with asthma or lung conditions should stay inside and keep medication close.

Pyroclastic flows and lahars: there is no outrunning them

The deadliest hazards move too fast to escape once they start, so survival depends entirely on not being in their path:

• Pyroclastic flows travel at 100+ km/h and reach 700°C. There is no surviving one at close range — the only defense is to have already evacuated the hazard zone.
• Lahars race down river valleys, sometimes far from the volcano. If you are near a stream or valley draining a volcano and feel strong shaking, hear a roar, or see the river rise suddenly, move to high ground immediately — climb the valley walls, do not try to outrun it downstream.

This is why heeding evacuation orders early is non-negotiable. By the time these hazards are visible, it is usually too late to flee. Review how they behave in our volcanic hazards guide.

Volcanic gas safety

Volcanic gases are an under-appreciated danger. Carbon dioxide is invisible, odorless, and heavier than air, so it collects in valleys, basements, and low ground — where it can suffocate without warning, as it did at Lake Nyos in 1986.

• Avoid low-lying areas near active vents, especially depressions and enclosed hollows.
• Leave immediately if you feel dizzy, short of breath, or notice a rotten-egg smell (hydrogen sulfide) — and move to higher ground.
• Heed "vog" (volcanic smog) advisories; sulfur dioxide aggravates asthma and heart conditions.

After an eruption

Hazards persist after activity ends. Ash remains a roof-collapse and health risk, and lahars can occur for months or years whenever heavy rain mobilizes loose ash deposits.

• Do not return home until authorities declare it safe.
• Wear protection during cleanup; ash is abrasive and irritating to lungs.
• Check roofs for ash load before re-entering buildings.
• Stay alert to rain-triggered lahar warnings in the months that follow.