United Kingdom
Gas leak and carbon monoxide
Use at your own risk. For education and research only, not medical advice. Check the numbers and rules for the country you are in. They change. Before you rely on these cards, have a medical professional or a fire safety specialist review them. Disclaimer
Do this first
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 a rotten-egg smell on purpose, so your nose works as the detector. Carbon monoxide has no smell, no colour and no warning, only a headache that gets better the moment you step outside. A single spark can ignite the first. A cheap detector is the way to catch the second.
Step by step
- Gas smell: stop and touch nothing electrical. No light switches, no doorbell, no lift button, no phone call inside the flat.
- Open windows and doors as you move towards the exit, so the gas thins instead of gathering.
- Close the main gas valve if it sits on your escape route, at the meter or the cylinder.
- Get everyone out and knock on neighbours' doors with your fist, not the bell. Call 999 and the gas emergency line from outside.
- Carbon monoxide: suspect it when several people and pets in the same room feel sick at the same time, with headache, nausea, dizziness or confusion that eases outdoors.
- Get everyone into fresh air at once, count heads and call 999. Say carbon monoxide, so the crew brings a meter.
- Nobody goes back in until the fire service has measured and cleared the space. The boiler, heater or flue that caused it stays off until a technician approves it.
Never do this
- Never flip a switch, light a flame or start a car inside a space that smells of gas. Switching a light off sparks just as switching it on does.
- 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 can mislead you.
Call emergency services if
- Any gas smell you cannot stop at once 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.
Common questions
Where do CO detectors belong, and how many?
Put one in every room with a fuel-burning appliance and one near each sleeping area. Mount them at breathing height, roughly one to two metres up, and do not fix them to the ceiling the way you would a smoke alarm. Replace each unit by the date printed on it, because the sensor wears out in five to ten years.
The smell is faint and I think it is just the cooker left on. Do I still follow 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 within minutes, or you cannot find an innocent source, treat it as a leak and call. Gas companies would rather take a hundred false calls than one explosion.
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Sources and standards
Use at your own risk. For education and research only, not medical advice. Check the numbers and rules for the country you are in. They change. Before you rely on these cards, have a medical professional or a fire safety specialist review them.