Chemical or industrial accident nearby: how to shelter in place and seal a room
What to do when you get an alert about a toxic cloud from a plant, train or tanker: how to shelter at home, how to seal a room, why not to go to the basement, when to evacuate and what to do if you've been exposed.
In short
- With a toxic cloud, staying indoors is usually safer than going out on the road. Get inside, close windows and turn off ventilation.
- Choose an interior room above ground with as few windows as possible. Don't go to the basement: many toxic gases are heavier than air.
- Seal the door and windows with tape and plastic sheeting, put a wet towel along the bottom of the door and listen to the radio.
- If told to evacuate, travel crosswind, not downwind.
Chemical accidents are rare, but they happen: an explosion at a plant, a tanker overturned on a highway, a derailed train carrying chlorine or ammonia, a warehouse fire. A toxic cloud can spread for miles in minutes. Most often, authorities don’t order evacuation but shelter in place: get inside and seal up as well as you can.
This guide is adapted from FEMA’s Ready.gov chemical emergency guidance, which is in the public domain.
When the alert comes
- Get inside the nearest building immediately. If you’re in a car, close the windows and turn off ventilation or set it to recirculate.
- Bring children and pets inside.
- Close all windows and doors.
- Turn off fans, air conditioning, range hoods and any system that draws in outside air.
- Close fireplace and stove dampers.
- Go to your chosen room and seal it.
- Listen to the radio, follow emergency alerts and only call the emergency number for a medical emergency: lines need to stay free.
Which room
- Interior, with as few windows and outside doors as possible.
- Above ground, not the basement. Many toxic gases, such as chlorine, are heavier than air and collect low. This matters: in a tornado, air raid or nuclear emergency the basement is good; in a chemical accident it isn’t.
- With access to water and a toilet if possible (a bathroom is often a good choice).
- Big enough for everyone: roughly 10 sq ft (1 m²) per person for a few hours.
How to seal the room
- Heavy plastic sheeting over windows and vents, taped down on every edge.
- Duct tape over every gap around the door.
- A wet towel along the bottom of the door.
- Cover outlets on exterior walls and gaps around pipes.
Keep a roll of plastic sheeting, wide duct tape and a few old towels at home. Pre-cut sheeting to fit the windows in your chosen room and label where each piece goes.
What to take into the room
- Drinking water and some food
- Phone, charger and a battery radio
- Flashlight
- Daily medication
- First aid kit
If you’re told to evacuate
- Travel crosswind: not downwind, and not upwind through the cloud.
- Follow the routes authorities give.
- Close car windows and set ventilation to recirculate.
- See also the evacuation checklist.
Signs of exposure
Stinging or watering eyes, coughing, trouble breathing, sore throat, headache, dizziness, nausea, burning or irritated skin. Leave the contaminated area, remove outer clothing, wash with soap and water and call the emergency number.
Prepare
- Find out whether you live near a hazardous facility: ask your local emergency management office.
- Learn your local warning signals. See our guide to sirens and emergency alerts.
- Pick your room in advance and prepare sealing materials.
Frequently asked questions
How long do I stay sheltered?
Usually a few hours, until authorities say the cloud has passed. A sealed room doesn't keep the air clean forever, so when you get the all-clear, open windows and ventilate thoroughly. Follow emergency alerts, radio and local TV.
How do I know if I live near a hazardous site?
In the EU, plants handling large amounts of dangerous substances fall under the Seveso Directive and must inform the public in their risk zone. In the US, Local Emergency Planning Committees (LEPCs) hold information on chemical facilities. Ask your local emergency management office.
What if I was in the cloud before I got inside?
Remove your outer clothing (cut it off rather than pulling it over your head) and seal it in a bag. Wash with soap and water without scrubbing hard. Rinse your eyes with clean water for 10–15 minutes if they sting. Call the emergency number if you have trouble breathing, chest pain, dizziness or burns.
Sources and further reading
Preper is for general education and does not replace instructions from your local authorities or advice from a doctor. In an emergency, call your local emergency number.