Gas leak & carbon monoxide
What to do if you smell gas or suspect carbon monoxide at home — the safe, fast steps and the free emergency numbers.
WHAT TO DO NOW
- 1If you smell gas or suspect a leak, call the free National Gas Emergency Service on 0800 111 999 (Great Britain) or 0800 002 001 (Northern Ireland) — 24 hours.
- 2Open doors and windows to let gas escape.
- 3Turn off the gas at the meter control valve if you can reach it safely.
- 4Do NOT touch electrical switches (on or off), use anything with a flame, or use phones inside the property — go outside first.
- 5Put out naked flames and do not smoke.
- 6Get everyone out and stay out until told it is safe; if anyone feels unwell, call 999.
What not to do
- Do not turn light switches or appliances on or off — a spark can ignite gas.
- Do not search for a leak with a naked flame.
- Do not re-enter the property until a Gas Safe registered engineer or the emergency service says it is safe.
- Do not ignore a carbon monoxide alarm — treat every activation as real.
What is it?
A gas leak is an escape of natural gas, which is highly flammable. Carbon monoxide (CO) is a separate, invisible danger — a poisonous gas with no smell produced by faulty or poorly ventilated gas, oil, wood or coal appliances.
What might happen?
A gas leak risks fire or explosion. Carbon monoxide poisoning can cause headaches, dizziness, nausea, breathlessness, collapse and can be fatal — symptoms can be mistaken for flu or tiredness and often affect several people (and pets) in the home at once.
First 10 minutes
For a gas smell: get everyone out, ventilate, turn off the meter if safe, avoid switches/flames/phones indoors, and call 0800 111 999 (GB) / 0800 002 001 (NI). For a CO alarm or CO symptoms: get fresh air immediately, leave the property, and call 999 if anyone is unwell.
First hour
Stay outside and wait for the emergency engineer. Do not use the appliance or supply. Seek medical advice for anyone who felt unwell — tell them you suspect carbon monoxide.
First 24 hours
Have the fault fixed by a Gas Safe registered engineer before using gas again. Fit or test an audible CO alarm to EN 50291 and service gas appliances annually.
If it continues for several days
Keep gas appliances serviced yearly by a Gas Safe registered engineer and keep CO alarms tested — prevention is the reliable protection.
Children
Get children and babies out first; CO affects small bodies faster.
Older & vulnerable people
Older people and those with heart or breathing conditions are more vulnerable to CO — check on them and ensure they have working alarms.
Pets
Get pets out too; unexplained illness in pets can be an early sign of carbon monoxide.
Communications
Once safely outside, phone the emergency number; never make the call from inside a property where gas may be present.
Official sources
This guidance is an editorial explanation of official UK advice. Always follow instructions from the authorities.
- GOV.UK — Prepare Published 2024-06-01
- NHS Published 2025-01-01
- Food Standards Agency — Food safety in a power cut Published 2025-01-01