Smell of Gas at Home: What to Do (Call 0800 111 999)

The five things to do, in this order

Mains gas has no smell of its own. The rotten-egg or cabbage smell is an odorant added so that a leak can be noticed before it builds up. If you can smell it, act on it, even if it seems faint or comes and goes.

• Open doors and windows to let the gas disperse. Do it as you move through the house, without stopping to search for the source
• Turn the gas off at the emergency control valve by the meter, if you can reach it safely, so the lever sits across the pipe. If the meter is in a cellar or basement, do not go down to it; just leave
• Do not operate anything electrical: light switches (on or off), doorbells, extractor fans, the boiler controls, or anything else that could spark
• No naked flames: do not smoke, strike a match or light the hob to "check"
• Get everyone outside, then call 0800 111 999 once you are away from the smell, and wait there until the engineer says it is safe to go back in

0800 111 999 is the National Gas Emergency Service. It is free, open 24 hours, and the right number even if you are not sure the smell is gas. A plumber, heating company or landlord is not the first call.

What the gas emergency engineer does when they arrive

In London the call is passed to the gas network for your area: Cadent covers north London and SGN covers south London. Their emergency engineer will find the source of the smell with a gas detector and make the property safe. There is no charge for this.

If the leak is on the network’s own supply pipe, they repair it. If it is on your side, on the pipework inside the property or on an appliance, their job is usually to make safe rather than repair. That usually means shutting off and capping the leaking appliance, or leaving the whole supply off, and fixing a warning label to it.

The label itself reads "Danger, Do Not Use", and the warning notice records one of two categories under the gas industry’s unsafe situations procedure. "Immediately Dangerous" means the appliance or pipe has been disconnected and must not be used. "At Risk" means it has a fault that could become dangerous, and it will be turned off with your permission. Either way the label is the start of the job, not the end of it.

Do not remove the label or reconnect anything yourself. Using a gas appliance you have been told is dangerous puts you and your neighbours at risk, and in a rented home the landlord has a legal duty under the Gas Safety (Installation and Use) Regulations 1998 to put right the pipework and any appliance they provided.

After the emergency visit: getting the gas back on

If the network has fixed the fault on their side, they will turn the supply back on and check that every appliance lights properly. If the problem is on your pipework or an appliance, you will be left with the gas off, or with one appliance capped, until it has been repaired.

That repair has to be done by a Gas Safe registered engineer, and it is worth checking the engineer’s card on the register before they start. Our guide on checking an engineer on the Gas Safe Register shows what the card should say for boiler, cooker or fire work.

The engineer starts with a tightness test on the whole installation: a pressure gauge (a manometer) goes on the test point by the meter and they watch for a pressure drop over a couple of minutes with every appliance off. If it drops, they trace the leaking joint with leak detection fluid or an electronic detector. Once it is repaired, the test is repeated, the supply is purged of air and each appliance is relit and checked.

If the fault was in the boiler, the repair is a boiler repair like any other once the leak is found. Our emergency boiler repair visit covers that: the £60 call-out gets an engineer to you, and the repair price is agreed on site before any work starts. Gas work is carried out by Gas Safe registered engineers.

Where gas smells usually come from

The emergency engineer will find it, but knowing the common sources helps you describe what happened on the phone.

• A hob tap turned slightly on without a flame, often knocked by a child or a pan. Very common, and the smell clears quickly once the tap is off
• A worn flexible hose or bayonet connector behind a freestanding cooker, especially after the cooker has been pulled out to clean
• A leaking joint on the gas pipe to the boiler, often after other work nearby
• A loose or corroded fitting on the meter or the pipe just after it
• A gas fire whose flame safety device has failed, so gas keeps flowing after the pilot has gone out
• Outside: a leak on the supply main in the street, which may smell strongest at the front of the house or near a drain

Sulphur-type smells can also come from drains or from hot water with a bacteria problem. If you are not sure, treat it as gas and follow the steps above, call to 0800 111 999 included. They would rather attend a false alarm.

Smell of gas and a headache? It may be carbon monoxide too

Carbon monoxide has no smell at all, so a gas smell is not a sign of it. But a faulty appliance can be leaking gas and burning badly at the same time. If anyone in the home has a headache, dizziness, nausea or breathlessness that eases when they go outside, open windows, turn the appliance off, get outside, tell the 0800 111 999 operator and get medical advice from NHS 111, or 999 if someone is confused, collapses or has chest pain.

The warning signs on the appliance itself, and where a CO alarm should go, are covered in carbon monoxide from a boiler.

Living in a flat: what changes

In a block, the meters may be in a shared meter room or cupboard on the landing, and you may not be able to reach your own control valve. Do not go looking for it if the smell is strong; leave and call from outside.

Warn neighbours on your way out by knocking, not by pressing electric doorbells. If the smell is in the common parts rather than your flat, still call 0800 111 999 and then tell the managing agent. For who is responsible for what in a shared building, see plumbing emergencies in a block of flats.