Immediate danger to life: call 999 or 112.

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Gas leak & carbon monoxide

Sources checked 1 June 2026

Action summary

  1. If 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.
  2. Open doors and windows to let gas escape.
  3. Turn off the gas at the meter control valve if you can reach it safely.
  4. Do NOT touch electrical switches (on or off), use anything with a flame, or use phones inside the property — go outside first.
  5. Put out naked flames and do not smoke.
  6. Get everyone out and stay out until told it is safe; if anyone feels unwell, call 999.

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

Keep gas appliances serviced yearly by a Gas Safe registered engineer and keep CO alarms tested — prevention is the reliable protection.

Sources

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