Smell of Gas From Your Boiler? Emergency Steps & Who to Call

I can smell gas — what do I do right now?

A gas leak is a fire and explosion risk, so treat any gas smell as urgent. Work through the steps below in order. These are the recognised public-safety steps from the National Gas Emergency Service and the HSE — for anything beyond turning off the supply at the meter, wait for the emergency engineer.

If anyone feels dizzy, sick or breathless, treat it as serious and get medical help. If there's a fire or you think there's an immediate danger to life, call 999.

Call the National Gas Emergency Service: 0800 111 999

The number to call across England, Scotland and Wales is 0800 111 999. The call is free, the line is staffed 24 hours a day, 7 days a week, and it's run on behalf of your local gas distribution network — in Great Britain that's Cadent, SGN, Northern Gas Networks or Wales & West Utilities, depending on where you live.

When you call, the operator will typically ask:

• The address and postcode where you can smell gas.
• Whether the smell is inside or outside, and how strong it is.
• Whether anyone feels unwell.
• Whether you've been able to turn the gas off at the meter.

An emergency engineer is then dispatched. The networks aim to attend an uncontrolled gas escape within around 1 hour, and a controlled escape (for example where you've turned the gas off at the meter) within around 2 hours. Their job is to make the situation safe before they leave. If you're deaf, have hearing loss or are speech-impaired, you can use Relay UK by dialling 18001 then 0800 111 999.

How to turn off your gas at the meter

The shut-off is called the emergency control valve (ECV). It sits next to your gas meter and has a small lever handle, usually red (sometimes black or yellow).

To turn the gas off, give the handle a quarter turn — 90 degrees:

• Gas ON: the handle lies in line with (parallel to) the gas pipe.
• Gas OFF: the handle sits across the pipe, at a right angle to it.

So if the lever is pointing the same way as the pipe, turn it a quarter-turn so it points across the pipe. Only do this if the meter is safe and easy to reach — if it's in a cellar or you'd have to use a light or torch switch to get to it, leave it and get out instead.

Once it's off, leave it off until the emergency engineer or a Gas Safe registered engineer tells you it's safe to restore the supply. Turning the ECV is the only gas action you should take yourself — everything beyond it is a job for a Gas Safe registered engineer.

What gas actually smells like

Natural gas is naturally colourless and odourless. To make leaks noticeable, suppliers add a tiny amount of an odorant (a sulphur compound such as mercaptan), which gives gas its distinctive "rotten eggs" or sulphur smell.

That eggy smell is the warning sign. Don't confuse it with two harmless lookalikes:

• Drains: a sewage or eggy smell that's worse near a plughole or after running water is usually a drainage or trap issue, not gas.
• Hot water that smells of eggs: this is often bacteria in the hot-water system or a reaction in a stored cylinder — a plumbing matter, not a gas leak.

If in any doubt, treat it as gas and call 0800 111 999. It's free, and the operators would far rather attend a false alarm than miss a real leak.

Gas leak vs carbon monoxide — the critical difference

People often muddle these two, but they're completely different hazards and you detect them in different ways.

	Gas leak (natural gas)	Carbon monoxide (CO)
Smell	Rotten eggs / sulphur (added odorant)	None — odourless, colourless, tasteless
Cause	Unburnt gas escaping from a pipe, joint or valve	Incomplete combustion from a faulty or poorly ventilated appliance
Main danger	Fire and explosion	Poisoning (the ONS records on average around 60 accidental CO deaths a year in England & Wales)
How to detect	Your nose, plus a hissing sound	An audible CO alarm — you cannot smell it
What to do	Ventilate, evacuate, call 0800 111 999	Get fresh air, seek medical help, call 0800 111 999

Because CO has no smell, an alarm is your only reliable warning. Read more about carbon monoxide from your boiler — the silent, odourless danger.

Warning signs of a gas leak

The smell is the headline sign, but watch for these too:

• A hissing or whistling sound near a pipe, the meter or an appliance.
• A lazy yellow or orange flame on the boiler or hob instead of a crisp blue one.
• Sooty marks, scorching or staining around the boiler.
• Dead or yellowing patches of grass or plants above an underground gas pipe outside.
• Excessive condensation on windows in the room with the appliance.
• Physical symptoms — dizziness, headaches, nausea or tiredness that ease when you leave the house.

Note that a yellow flame, soot and condensation can also point to incomplete combustion and a carbon-monoxide risk, so don't ignore them.

What causes a gas smell from a boiler

A genuine gas smell around the boiler usually traces back to escaping unburnt gas. Common causes include:

• A loose, corroded or damaged gas pipe or a failed compression joint.
• A faulty gas valve that isn't sealing properly.
• A worn seal or gasket on the burner or combustion chamber.
• A poor or non-compliant installation, where fittings weren't tightened or tested correctly.
• A cracked heat exchanger (this is also a carbon-monoxide concern).

All of these are sealed-circuit, burner, flue or gas-valve faults — strictly work for a Gas Safe registered engineer, never DIY. One smell that's usually harmless: a faint burning or dusty odour when the heating fires up for the first time in autumn. That's dust burning off the heat exchanger and clears within a few minutes — it's quite different from a sharp, eggy gas smell. If you're not sure, see our guide to emergency boiler repairs: what to do right now.

What happens when the engineer arrives

The emergency engineer's role is to make the situation safe, not to repair your boiler. When they arrive they will typically:

• Test the air for gas and check the meter and your pipework for escapes.
• Trace the source of the leak.
• Make the installation safe.

Crucially, if the fault is on your side of the meter — your pipework or your appliance — they may cap or disconnect the supply to that part and attach a warning label. That keeps you safe, but it can leave you without heating and hot water until you arrange a repair.

In other words, the emergency visit stops the danger; it does not put your boiler back into service.

Who pays for the repair?

This is the part most guides skip, and it matters. The split is straightforward:

Who does what	Who pays
National Gas Emergency Service attends & makes safe	Free of charge
Leak on the gas network or at the meter / ECV	The gas network (free to you)
Leak in your own pipework or boiler	You — via a Gas Safe registered engineer

So the emergency response is free, but once the fault is inside your property and on your appliance, the repair is yours to arrange and pay for. As a rough, indicative guide for 2026 (prices vary by region, engineer and the specific fault — always get a written quote), a minor pipe or joint repair often runs from around £80 to £150, larger boiler faults can be £150 to £350+, and replacing a major part such as a heat exchanger commonly runs £400 to £750+. See our breakdown of typical boiler repair costs in 2026.

Whatever happens, only ever let a Gas Safe registered engineer (and how to check) work on the gas side. This is exactly where having cover in place can take the sting out of the bill.

Does boiler cover pay for a gas leak repair?

Often, yes — but always check the wording. Most boiler cover and home-emergency products are built around your boiler and central-heating system, and many also include internal gas pipes and the flue. That can mean the repair after a leak is covered, subject to the policy or plan terms.

Watch the usual exclusions, though: pre-existing faults, boilers over a certain age, lack of an annual service, and gas pipework beyond a stated point can all be carved out. We can't say whether your own situation would be covered — always confirm on the provider's own page and read the terms before you rely on it.

It's also worth knowing the difference between the two product types — see boiler cover vs home emergency insurance and our wider explainer on gas boiler insurance and what it covers. When you're ready, you can compare boiler cover for 2026 from our selected panel of providers.

Landlords and tenants

Rented homes carry extra duties under the Gas Safety (Installation and Use) Regulations 1998:

• Landlords must arrange an annual gas safety check on every gas appliance and flue by a Gas Safe registered engineer, and keep the resulting record (often called the CP12 / Landlord Gas Safety Record) for at least 2 years. A copy must be given to tenants — within 28 days of the check for existing tenants, and before move-in for new ones.
• Tenants must report any gas smell or suspected fault straight away — call 0800 111 999 first if you can smell gas, then tell the landlord or letting agent.

For the paperwork and costs, see the gas safety certificate (CP12) landlords need.

How to reduce the risk of gas leaks

You can't eliminate the risk, but you can cut it sharply:

• Service your boiler every year with a Gas Safe engineer, who checks pipes, seals and combustion — see an annual boiler service helps prevent leaks.
• Only ever use a Gas Safe registered engineer for any gas work — never DIY it and never use an unregistered tradesperson.
• Fit a carbon monoxide alarm to BS EN 50291 near each gas appliance, and test it regularly.
• Don't ignore the early signs — yellow flames, soot, hissing or recurring headaches all warrant a professional check.

This article is general information, not financial or gas-safety advice. We compare a selected panel of providers, not the whole market, and may earn a commission if you buy through our links. Always have gas appliances checked and repaired by a Gas Safe registered engineer; in a gas emergency call 0800 111 999. Prices are indicative UK guides for 2026 — confirm current prices on the provider's own site.