Safety guide · Based on official sources

What to Do in a Chemical Attack: Go Up, Get Inside, Seal the Room

▶ PLAY FREE NOWNo download · Phone or PC · 3–5 minutes per run · 10 languages

What to do in a chemical attack or chemical emergency is, in key ways, the opposite of what to do in a nuclear attack. For an air raid or nuclear alert you go underground. For a chemical alert you go indoors and up high, somewhere sealed from outside air, because most chemical vapors are heavier than air and pool in low places like basements. This guide walks through each step in the order you'd face it, with the reason and the official source.

1. When the alert sounds: check which one

In South Korea, chemical alerts are announced by voice broadcast and emergency text message (Dobong-gu Office, Gyeonggi Safety Experience Center). Because the right action is the opposite of an air-raid alert (which means go underground), check the alert type in the text message or broadcast first. Even without an alert, suspect a chemical incident if several people suddenly have trouble breathing, vomit or break out in rashes, or birds fall for no reason (Seoul Metropolitan Government).

In airports, stations and other transport hubs, follow announcements and staff instructions and move in an orderly way (a general principle from Incheon Metropolitan City's emergency response guidelines). Phone networks jam during disasters, so send family short text messages instead of calling (Korea Ministry of the Interior and Safety, National Disaster Safety Portal).

2. Protect your breathing first

Wear a gas mask if you have one. If not, cover your nose and mouth with a face mask, a wet towel or a handkerchief (Seoul Metropolitan Government). It won't block everything, but it reduces how much you inhale in the minutes it takes to get away.

3. Go up and get inside: avoid underground spaces

Seoul's guidance says that if you're in a building, move to a higher place where outside air is blocked. Guri City's guide likewise points people to high ground or the inside of tall buildings. An uncontaminated area or a building's upper floors is best (Seoul Metropolitan Government).

• Stay out of subway stations, underground parking and other below-ground spaces. Heavy vapors collect there first (US CDC).
• Move away from the reported contamination point. Even inside the same building, the far end is better.
• Take the stairs, not the elevator. Crowded elevators are slow, and if one stops you're trapped.
• An open rooftop is not a shelter. You want high and indoors.
• If you're in a car, get into a building if you can. If you must stay in the car, close the windows and vents and turn off the air conditioner or heater (Ready.gov).

4. Choose a room and seal it

The US CDC recommends sheltering in place in a room on the highest floor possible, with few windows and access to water. Once inside, shut out the outside air:

• Close doors, windows and vents (Guri City, Dobong-gu).
• Turn off air conditioning, fans and ventilation. In a large building, ask staff or building management to shut off the ventilation system.
• Seal the gaps with tape. Block the bottom of the door with wet towels or clothing, and tape plastic sheeting over windows and vents (US CDC).
• Listen for official updates by radio or phone. Save your phone battery.

5. If you were exposed, decontaminate right away

Contaminated clothing and skin keep exposing you. Wash as soon as you're inside.

• Don't pull clothing over your head. Cut it off so nothing touches your face (US CDC).
• Seal the clothes in two plastic bags and put them away from people (US CDC, Guri City, Seoul).
• Wash with soap and running water for at least 15 minutes (Dobong-gu, Guri City). Don't scrub your skin hard (US CDC).
• If it got in your eyes, rinse with clean water for 10–15 minutes. No eye drops, no rubbing. Remove contact lenses and throw them away with the clothes (US CDC).
• People coming in from outside should take off outer clothing at the door and wash before joining the room. One contaminated person can expose everyone inside.

6. If someone has symptoms or collapses

Runny nose, watery or stinging eyes, coughing, chest tightness and difficulty breathing are signs of possible exposure. Move a contaminated person to an uncontaminated place, give first aid and alert emergency services and medical staff (Dobong-gu Office). Tell the dispatcher (119 in Korea, 911 in the US) the location, the symptoms and how many people are affected, and follow their instructions. Don't take or give any medication on your own.

7. While you wait inside

Sheltering in place can last from a few hours to a few days. Stay until authorities say it's safe (US CDC). Walking out after a couple of hours because “it's probably fine now” is one of the most dangerous mistakes.

• Listen to official broadcasts and watch out for social media rumors (Seoul Metropolitan Government). Don't act on unsourced messages like “they say go underground.”
• Keep the door shut. Opening it “just for a bit of air” breaks the seal.
• Contact family by text. Don't go outside to look for them; everyone shelters where they are.

8. Moving after the all-clear

When the all-clear comes, go to the designated decontamination or relief site. Outdoors, move against the wind; if the wind is blowing from the contaminated area toward you, move to the left or right of it (crosswind) (Seoul Metropolitan Government, Dobong-gu). Ready.gov likewise advises moving upwind of the source. Skip the nearest exit if the wind blows toward it, and avoid underground passages where gas may linger.

How this differs from nuclear attack shelter

• Where: nuclear fallout, deep underground / chemical attack, upper floors indoors.
• What you block: nuclear, radiation, with thick earth and concrete / chemical, air, by sealing gaps and vents.
• What you turn off: both, ventilation, to cut outside air.
• Clothing: both, remove outer clothes, seal them in plastic and wash.
• When to leave: both, only when officials say to move.

That's why the first step is always checking the alert type in official texts and broadcasts. For nuclear attacks, see what to do in a nuclear attack from the same series.

Chemical emergency kit

• Face masks (a gas mask if possible)
• Wide tape
• Plastic sheeting and bags (sealing, clothes)
• Towels (to wet)
• Bottled water (incl. for washing and eyes)
• Scissors (to cut off clothing)
• Soap and rubber gloves
• Battery radio and spare batteries
• Flashlight and power bank
• Basic medicines and ID

Store at least three days of supplies

For days after a disaster, power, water and phone service may be out and shops closed. In October 2026, Japan's government (with the launch of its new disaster management agency) and the UK government (Be Ready campaign) renewed their advice that every household keep at least three days, ideally a week, of water and food. Korea's National Disaster Safety Portal emergency kit list points the same way.

• Water: about 3 L per person per day × at least 3 days. Keep extra after a chemical incident, since you'll need water for washing too.
• Food: ready-to-eat items like canned food, instant rice, energy bars and crackers.
• Portable toilet, plastic bags, wet wipes: the first things you miss when sheltering for a long time.
• Flashlight, power bank, battery radio, spare batteries: hearing official broadcasts matters most.
• Basic medicines, masks, tape, some cash, copies of ID.

No need to panic-buy. Add a little each time you shop, then eat and replace it (rotating stock).

Practice it in a simulation

Knowing “chemical means go up” is one thing. Pushing up the stairs while everyone around you is shouting “get underground!” is another. Incheon Airport Chemical Attack: 10 Minutes Until the Gas Arrives is a free browser game where you make these decisions against the clock in a fictional version of Incheon Airport's departures hall. See the game guide.

Sources

• Seoul Metropolitan Government, “What to Do During a Chemical/CBR Alert” (emergency public action guide) and “What to Do in a CBR Situation”
• Dobong-gu Office, action guides by disaster type (emergency preparedness, CBR)
• Guri City, “Wartime CBR Action Guide”
• Gyeonggi Safety Experience Center, “Types of Civil Defense Alerts”
• Korea Ministry of the Interior and Safety, National Disaster Safety Portal (emergency action guides, emergency kit)
• Incheon Metropolitan City emergency response guidelines (general principles for transport facilities)
• US CDC, “Shelter in Place for a Chemical Emergency” and guidance on personal cleaning and clothing disposal after a chemical emergency
• Ready.gov, “Chemical Emergencies”

This page is general educational information, not official government guidance. In a real emergency, follow official alerts and broadcasts, facility announcements and staff instructions.

FAQ

▶ PLAY: INCHEON AIRPORT CHEMICAL ATTACK, 10 MINUTES UNTIL THE GAS ARRIVES