Gas Emergency — Act Now
If you can smell gas right now, call the National Gas Emergency Service immediately: 0800 111 999
Free, 24 hours a day, 7 days a week. Do not use any electrical switches before calling.
Quick Answer
If you smell gas: don't touch any switches, open windows and doors, turn off the gas at the meter, leave the building, and call 0800 111 999 (National Gas Emergency Service). Do not re-enter until told it's safe by an engineer in 2026.
Smelling gas in your home is a serious emergency. Natural gas itself is odourless — the distinctive “rotten egg” or sulphur smell is added deliberately by gas suppliers (it's called mercaptan) so leaks can be detected. If you can smell it, there's a gas leak, and every second counts. This guide tells you exactly what to do — and what not to do — when you smell gas in your home in 2026.
In this guide
Immediate Steps: What to Do If You Smell Gas
Follow these steps in order. Do not stop to make other phone calls, collect belongings, or investigate the source of the leak.
Do NOT touch any electrical switches
Do not turn lights on or off, do not press doorbells, do not use your phone or any electrical device inside the property. A single spark from a light switch can ignite gas that has built up to explosive concentrations. Leave lights as they are — on or off.
Open windows and doors immediately
Ventilating the building reduces gas concentration and lowers the risk of ignition. Open windows and external doors as wide as possible to let fresh air in and gas out. Do not open internal doors between gas-filled rooms and stairwells if you suspect a serious build-up.
Turn off the gas at the emergency control valve
Your emergency control valve (ECV) is located next to your gas meter — typically under the stairs, in a hallway cupboard, outside in a meter box, or in the kitchen. Turn the handle a quarter turn until it is at right angles (90°) to the pipe. This shuts off all gas to the property.
Leave the building immediately
Get everyone — including pets — out of the property. Leave the front door open behind you (to allow further ventilation). Do not go back inside. Do not use the lift in a block of flats — use the stairs.
Call 0800 111 999 from outside
Once you are safely outside, call the National Gas Emergency Service on 0800 111 999. This line is free, available 24/7, and connects you directly to trained emergency operators who will advise you and dispatch a gas engineer to your property. Do not call from inside the building.
Do not re-enter until cleared safe
Wait outside until a National Gas Emergency Service engineer has attended, assessed the situation, and confirmed it is safe to re-enter. Do not let anyone else enter the property either.
What NOT to Do When You Smell Gas
These actions could trigger an explosion or fire, or make the situation worse:
- Do NOT use any electrical switches — Lights, fans, cooker hoods, kettles, or any switch in the property. Even pressing a doorbell can ignite gas.
- Do NOT use a naked flame — No matches, lighters, candles, or cigarettes in or near the building.
- Do NOT use your mobile phone inside the building — Call from outside only. The signal from a phone is considered a minimal risk, but safety guidance is to use it outside to be certain.
- Do NOT try to find the source of the leak yourself — You are not equipped to safely identify or fix a gas leak. This is what the emergency service is for.
- Do NOT turn the gas back on yourself — Even if the smell has gone, only a Gas Safe registered engineer can declare the installation safe and turn the supply back on.
- Do NOT attempt to repair anything — Not the boiler, not the pipework, not the appliances. Wait for a professional.
- Do NOT delay — Gas leaks can become critical very quickly. Every minute matters.
After the Emergency
Once the emergency gas engineer has attended and made the property safe, you'll receive advice on next steps. This may include:
- Gas left switched off until a repair is made — the engineer will tell you which appliance or section of pipework caused the leak
- Immediate condemnation of a specific appliance if it's been found to be Immediately Dangerous (ID)
- A requirement to have a Gas Safe registered engineer carry out repairs before the supply can be reconnected
- Advice on carbon monoxide alarms — if you don't have one, install one immediately
After any gas incident, always arrange a full gas safety check of your property. This covers every appliance, flue, and metre of pipework. Read our guide on what a gas safety check covers and how to book one. And to find a trustworthy Gas Safe engineer for the follow-up work, read our guide on what to look for in a Gas Safe engineer.
Getting Appliances Checked After a Gas Incident
Any appliance that was involved in or near a gas incident must be professionally checked and signed off before being used again. Common causes of domestic gas leaks include:
- Corroded or damaged flexible gas hoses on cookers or appliances
- Loose fittings on pipework (particularly after DIY work involving nearby pipes)
- Faulty boiler components or pilot light failures with incomplete combustion
- Old or cracked pipework, particularly in pre-1970s properties
- Interference with gas supply pipes during building or renovation work
If your boiler is old or has been flagged for issues, a gas emergency is a prompt to consider whether it needs replacing. Read our guides on new boiler costs and signs your boiler needs replacing to help you decide.
| Emergency Contact | Number | When to Call |
|---|---|---|
| National Gas Emergency Service | 0800 111 999 | Any gas smell or suspected leak — FREE, 24/7 |
| Emergency services (fire/ambulance) | 999 | If fire has started, injury, or unconscious person |
| Non-emergency police | 101 | Gas-related crime or vandalism to meter |
| Your energy supplier | See back of bill | After emergency, to query meter or billing |
| Gas Safe Register | 0800 408 5500 | To report illegal gas work or verify an engineer |
Frequently Asked Questions
What does a gas leak smell like?+
Natural gas is odourless in its raw form. Gas suppliers add a chemical called mercaptan (or ethanethiol) to make leaks detectable — it smells like rotten eggs, sulphur, or a strong unpleasant chemical smell. Even a faint whiff of this smell indoors warrants immediate action. Don't dismiss it as 'probably nothing'.
Can carbon monoxide cause a gas smell?+
No — carbon monoxide (CO) is completely odourless and colourless. It's a separate danger from gas leaks, produced by incomplete combustion in poorly maintained or faulty boilers and appliances. CO cannot be smelled, which is why carbon monoxide alarms are essential in any home with gas appliances. A gas smell and a CO alarm going off are two different emergencies requiring the same immediate evacuation response.
What if the smell is faint and not certain?+
Treat any suspicion of gas as a confirmed gas emergency. The smell of mercaptan is detectable by the human nose at concentrations far below dangerous levels — so if you can smell it at all, there's a leak. Never wait to see if it gets stronger or try to investigate yourself. Call 0800 111 999 every time.
Is the National Gas Emergency Service free?+
Yes — 0800 111 999 is completely free to call, 24 hours a day, 7 days a week, including bank holidays. The initial emergency response — attending to make the property safe — is also free. You will be charged for any repairs needed to your pipework or appliances after the emergency, which must be carried out by a Gas Safe registered engineer.
Can I turn the gas back on myself after a gas engineer has attended?+
Only if the engineer has told you it's safe to do so. The engineer will either turn the gas back on themselves before leaving (if the issue is resolved), or advise you that it must remain off until a specific repair is made. Never turn the gas back on yourself after an emergency without explicit clearance from a Gas Safe registered engineer.
What causes most domestic gas leaks in the UK?+
The most common causes are: worn or damaged flexible hoses connecting appliances, loose or corroded pipe fittings, poorly maintained or ageing boilers, and accidental damage to pipework during renovation or DIY work. Annual boiler servicing by a Gas Safe engineer is the most effective prevention — it catches deteriorating components before they cause a leak.
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