Smell Gas in the House or Near Your Boiler? What to Do Now

If you smell gas in the house or near your boiler, turn the gas off at the meter, open doors and windows, do not use electrical switches or anything that could spark, and call the National Gas Emergency Service on 0800 111 999. If the smell is strong, get everyone out and make the call from outside. The emergency service is free and runs day and night. The boiler only needs a repair engineer once the supply has been made safe.

What Should You Do If You Smell Gas?

Act first and work out the cause later. These are the standard gas safety steps in Great Britain, and the order matters.

1. Do not create a spark. Do not switch lights or appliances on or off, do not use a doorbell, and do not smoke or strike a match. Leave switches as they are.
2. Turn the gas off at the meter if you can reach it safely. The emergency control valve is a lever on the pipe next to the meter. Turn it so it sits across the pipe rather than in line with it.
3. Open doors and windows to let the gas clear.
4. Get people out if the smell is strong, and keep them out.
5. Call 0800 111 999 from outside the property, on a mobile or from a neighbour's phone.
6. Get medical advice if anyone feels dizzy, sick, drowsy or has a headache.

Do not go looking for the leak, and do not turn the gas back on until you are told it is safe.

What Happens When You Call the Gas Emergency Number?

The emergency service sends an engineer from the local gas network to make the supply safe. Their job is to remove the danger, not to repair your boiler or other appliances.

They will work out whether gas is escaping from the network pipes in the street, the meter, or the pipework and appliances inside your home. If the problem is on your side of the meter, they will usually isolate the faulty appliance or turn the supply off and leave it off. The visit does not cost you anything. The repair is then yours to arrange with a Gas Safe registered engineer.

If an appliance is disconnected, it will normally be labelled with a warning notice. Our guide to what a boiler warning notice means explains the Immediately Dangerous and At Risk labels. Do not reconnect it or use it until it has been repaired and checked.

Why Would a Boiler Smell of Gas?

A gas smell at the boiler usually means gas is escaping from a joint, fitting or component on the supply to the boiler or inside it. Finding and fixing it is gas work, which must be done by a Gas Safe registered engineer.

• A loose or failed joint on the gas pipe below the boiler or at the gas isolation valve.
• A fault in the gas valve or one of its seals inside the boiler.
• Delayed ignition, where gas builds up for a moment before it lights. It is often heard as a thud or bang on start-up as well as smelt. Our guide to boiler ignition faults explains what sits behind it.
• Flue problems: a damaged or badly sealed flue can let combustion fumes into the room. They smell different from raw gas but are just as serious.
• Another appliance: a gas hob, cooker or fire with a worn tap can be the real source, even when the boiler gets the blame because it sits nearby.

Whatever the cause, the boiler should stay off until an engineer has checked it. This is not a fault to investigate with the case open or a spanner on the gas pipe.

Is It Gas, or Something That Smells Like It?

Mains gas has no smell of its own; a chemical is added so that leaks smell of rotten eggs or sulphur. A few other things smell similar, but if you are not sure, treat it as gas and make the call.

• Drains: a dried-out trap on a rarely used sink, shower or floor drain can let sewer gas in, which also smells of rotten eggs. It is usually strongest right by the outlet.
• Burning dust: the first time the heating runs in autumn, dust on radiators and inside the boiler can give off a brief scorched smell that fades within a day or so.
• Hot electrics: a fishy or burning plastic smell near the boiler points to an electrical fault rather than gas. Switch the boiler off and have it looked at.

The call costs nothing, and the emergency service would rather check a false alarm than miss a leak.

Can You Smell Carbon Monoxide?

No. Carbon monoxide has no smell, colour or taste, so a gas smell and a carbon monoxide leak are different problems. You can have one without the other.

Carbon monoxide comes from gas burning badly, usually because of a faulty appliance, a blocked flue or poor ventilation. Warning signs include headaches, dizziness, nausea, tiredness and breathlessness that ease when you are away from home, a lazy yellow or orange flame on a gas hob or fire, and dark sooty marks on or around an appliance. An audible carbon monoxide alarm is the only reliable way to detect it. If one goes off, treat it like a gas smell: turn the appliance off if it is safe to, open windows, get out, call 0800 111 999 and get medical advice.

What Happens After the Gas Has Been Made Safe?

Once the emergency engineer has made it safe, a Gas Safe registered engineer needs to find and repair the fault before the boiler or appliance goes back into use.

For a leak at or inside the boiler, the repair engineer will check the joints and gas valve, test the pipework for tightness and check the boiler burns correctly before putting it back into service. If the boiler was classed as unsafe and disconnected, it stays off until that work is done. In the meantime, electric heaters and, if you have a hot water cylinder, the immersion heater can keep the house going. If you rent, tell your landlord straight away, because keeping the gas appliances they supply safe is their responsibility.

Our emergency boiler repair service covers London once the supply has been made safe. When you contact us, tell us what the gas network engineer found and what the warning label on the boiler says.