Smell Gas in Your House? What to Do Right Now

Updated July 2026 · Emergency Plumber Chelsea

Mains gas has no smell of its own. Suppliers add a chemical odorant so that a leak is obvious, and it smells sharp and sulphurous, often described as rotten eggs or cabbage. If you notice that smell indoors, even faintly, treat it as a possible leak until someone qualified tells you otherwise. Most calls turn out to be something small, such as a hob knob knocked on without lighting, but you cannot tell that from the smell alone and the steps are the same either way.

Start with anything that can ignite gas. Put out cigarettes, candles and any open flame, and do not light a match or a lighter to look for the leak. Then let air in. Open doors and windows wide in the room where the smell is and on your way out, so that gas can disperse rather than build up. Gas collects fastest in small enclosed spaces, so kitchens, boiler cupboards and basements are where ventilation helps most.

Turn the gas off at the meter if it is safe and quick to do so. The emergency control valve is a lever on the pipe going into the meter. When the lever is in line with the pipe the gas is on; turn it a quarter turn so it sits across the pipe and the gas is off. In Chelsea the meter might be in a cupboard under the stairs, in a basement vault under the pavement, in a communal meter room in a mansion block, or in an external box by the front door. If you do not know where it is, or reaching it means going deeper into the smell, skip it and get out. Your safety matters more than the valve.

Do not operate anything electrical. That means no light switches on or off, no doorbells, no unplugging appliances and no using the lift in a block of flats. Flicking a switch can make a tiny spark, and in a room with a build-up of gas that spark is enough. Leave things exactly as they are. If the lights are already on, leave them on. Do not use your mobile phone inside the property either; wait until you are outside and away from the building.

Get everyone out, including pets, and do not go back in for belongings. Once you are outside, call the National Gas Emergency Service on 0800 111 999. They will ask for the address, where the smell is strongest and whether anyone feels unwell. An emergency engineer is sent to make the situation safe, which usually means finding whether gas is escaping, isolating the supply and capping off the faulty appliance or pipe. If you live in a flat, tell neighbours on your way out, and in a mansion block let the porter or managing agent know too, because a leak on a shared riser can affect more than one flat.

Watch for symptoms as well as smell. Headaches, dizziness, nausea, tiredness and breathlessness can all come from gas exposure or from carbon monoxide, which is produced when an appliance burns badly and has no smell at all. If you or anyone else feels unwell, get into fresh air and seek medical advice, and tell the doctor you think gas or carbon monoxide may be involved. If you have a carbon monoxide alarm sounding, treat it exactly as you would a gas smell. Every room with a gas boiler, fire or cooker should have an audible CO alarm, and it is worth testing yours now that the heating is going back on. Our guide to carbon monoxide from a boiler explains the warning signs to look for.

Not every eggy smell is gas, and it helps to know the common look-alikes, as long as you still call 0800 111 999 whenever you are unsure. A sulphur smell only from the hot taps is usually a reaction inside the hot water cylinder, covered in our guide to why hot water smells of eggs. A foul smell that comes and goes near a sink, shower or floor gully is more often a dry trap or a drain problem, explained in our drain smells guide. Gas usually smells strongest near the meter, the hob, the boiler or a gas fire, and does not disappear when you run a tap.

A faint smell around the cooker only when a burner is lit, which fades once the flame catches, can happen with a slow-lighting hob. A smell that lingers, gets stronger, or is there with every appliance off is different and needs the emergency line. The same goes for a hissing sound near a gas pipe or meter, or a boiler with a lazy yellow or orange flame instead of a crisp blue one, or dark staining around the boiler casing or a gas fire. These point to leaks or poor combustion and should never be left to the next service.

Once the emergency engineer has been, you may be left with the gas capped off at the meter or a single appliance marked as unsafe to use. They make the property safe but they do not carry out repairs. That is the point at which you need a Gas Safe registered engineer to trace the fault, repair the pipework or appliance and test the installation before the supply is turned back on. Emergency Plumber Chelsea does this through our gas leak detection service: a tightness test at the meter to confirm whether the installation holds pressure, leak-detection fluid and an electronic detector to pin down the joint or fitting, then the repair and a fresh test before anything is relit.

If the problem was the boiler, our engineers can repair it as part of our boiler repair service, and if water as well as gas is involved, see what to do if your boiler leaks. Landlords should keep the paperwork from any gas repair with their annual gas safety record; our gas safety certificate service covers both. Autumn is also the right time for a boiler service, because a Gas Safe engineer checks combustion and the flue, which is where carbon monoxide problems usually start.

Chelsea's housing has a few gas weak points worth knowing about. Period houses often have old iron or concealed pipe runs under floors and behind panelling, mansion blocks share gas risers, and basement flats can let gas collect in low, poorly ventilated rooms. Cooker hoses pulled out during a kitchen clean and loosened fittings after building work are also regular causes, which is why fitting a gas cooker yourself is best avoided. If you have had work done recently and now notice a smell, say so when you call, because it helps the engineer find the source faster.

If you have called 0800 111 999 and your gas has been made safe, call Emergency Plumber Chelsea on 020 3002 6667 to get it repaired and back on. We cover SW3, SW10, Knightsbridge, Sloane Square, South Kensington and Fulham from 189 Brompton Road, and every engineer we send for gas work is Gas Safe registered. There is no call-out fee on jobs over 3 hours.

Quick tips

• Smell gas: flames out, windows open, meter lever off if you can reach it quickly, then leave and call 0800 111 999 from outside.
• Do not touch light switches, plugs, doorbells or the lift, and do not use a phone until you are outside.
• Know where your meter and its emergency control valve are before you ever need them.
• Fit an audible carbon monoxide alarm in every room with a gas appliance and test it when the heating goes back on.
• After the emergency service has made it safe, a Gas Safe engineer must repair and test the installation before the gas is turned back on.

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