Carbon monoxide or gas leak: what to do? Step-by-step guide

⏱ 2 min read

Headache, smell of gas. Below: what to do right away, what next, when to call 112 and what to avoid. The same instructions are in the free SurvivalZone.app and work without internet.

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First, right now

Several people with a headache, dizziness, nausea or drowsiness, or the CO alarm is beeping? Open the windows and get everyone outside now.
Smell gas? Do not switch lights or appliances on or off and do not light anything. Close the gas valve if it is within reach.
From outside, call 112 or your gas emergency line.

Then

Warn neighbours by knocking on doors, not by ringing doorbells.
Carry an unconscious person into fresh air only if you can do it quickly. Check breathing; if they are not breathing, start CPR.
Even if symptoms go away in fresh air, anyone exposed to carbon monoxide needs to see a doctor.
Go back inside only when the fire service or gas engineers say it is safe.
For the future: fit a CO alarm near the boiler, stove or fireplace and in bedrooms, and have the chimney and boiler checked every year.

When to call 112

Always when you suspect carbon monoxide or smell gas. Immediately if someone is unconscious, confused or having a seizure.

What not to do

Do not use your phone, a doorbell or a torch in a room with gas. A spark can cause an explosion.
Do not look for a leak with a match or lighter.
Do not go back in for belongings or pets.
Never heat your home with a gas cooker, barbecue or generator indoors.

Frequently asked questions

Carbon monoxide or gas leak: what should I do first?

Several people with a headache, dizziness, nausea or drowsiness, or the CO alarm is beeping? Open the windows and get everyone outside now. Smell gas? Do not switch lights or appliances on or off and do not light anything. Close the gas valve if it is within reach. From outside, call 112 or your gas emergency line.

When should I call 112?

Always when you suspect carbon monoxide or smell gas. Immediately if someone is unconscious, confused or having a seizure.

Carbon monoxide or gas leak: what should I avoid?

Do not use your phone, a doorbell or a torch in a room with gas. A spark can cause an explosion. Do not look for a leak with a match or lighter.

Keep it on your phone

SurvivalZone.app is a free app for every emergency, with no account and no app store. It works without internet and shows the nearest shelters and help points, local radio, a 72-hour plan and a mountain trip planner.

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Thank you for reading. If this could help someone, send it to the people you care about. Getting ready takes a moment, and in a crisis every minute counts.

Coming soon: the app’s permanent address will be survivalzone.app.

Other scenarios

Sources

Scientific literature and guidelines

Official sources are checked automatically every day. Last check: 2026-11-08.

General guidance only; it does not replace the emergency services. If a life is in danger, call 112.