# Gas leak and carbon monoxide

> If you smell gas, do not touch any switch or flame. Open windows and doors on your way out, close the gas valve if it is on your path, and call from outside.

Natural gas is given its rotten-egg smell on purpose, so your nose is the detector. Carbon monoxide is the opposite: no smell, no colour, no warning, just a headache that gets better the moment you step outside. One spark handles the first, one cheap detector handles the second.

## Step by step
1. Gas smell: stop, and touch nothing electrical. No light switches, no doorbell, no lift button, no phone call inside the flat.
2. Open windows and doors as you move towards the exit, so the gas thins instead of gathering.
3. Close the main gas valve if it sits on your escape route, at the meter or the cylinder.
4. Get everyone out, knock on neighbours' doors with your fist, do not ring the bell, and call 112 and the gas emergency line from outside.
5. Carbon monoxide: suspect it when several people and pets feel sick in the same room at the same time, with headache, nausea, dizziness or confusion that eases outdoors.
6. Get everyone into fresh air at once, count heads, and call 112. Say carbon monoxide, so the crew brings the meter.
7. Nobody goes back in until the fire service has measured and cleared the space, and the boiler, heater or flue that caused it stays off until a technician passes it.

## Never do this
- Never flip a switch, light a flame or start a car inside a space that smells of gas. Turning a light off sparks the same as turning it on.
- Never sleep in a room with a running combustion heater, charcoal grill or generator, and never let an engine run in a closed garage.
- Never silence a beeping CO detector because you feel fine. Get out first and doubt it later, low doses lie.

## Call emergency services if
- Any gas smell you cannot stop immediately at the valve, and any smell in a cellar or stairwell.
- Anyone confused, fainting or vomiting in a room with a boiler, heater or fire.
- A CO detector alarm, even if everybody feels healthy.

## Emergency numbers
112 - Single European emergency number

## Common questions
### Where do CO detectors belong, and how many?
One in every room with a fuel-burning appliance and one near each sleeping area, mounted at breathing height, roughly one to two metres up, not glued to the ceiling like a smoke alarm. Replace the unit by the date printed on it, the sensor wears out in five to ten years.

### The smell is faint and I think it is just the cooker left on. Still the whole routine?
Turn the cooker off, open the windows and step out while it clears, still without touching other switches. If the smell does not fade in minutes, or you cannot find an innocent source, treat it as a leak and call. Gas companies genuinely prefer a hundred false calls to one explosion.

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Use at your own risk. Educational and research use only, not medical advice. Verify numbers and rules for the country you are in. They change.
Source: https://emergency-cards.com/en/gas-leak/
Reviewed: 2026-07-26