A suspected gas leak is a life-safety emergency requiring immediate action. In London, call the National Gas Emergency Service on 0800 111 999 immediately. This guide covers the correct emergency response, what to do before the engineer arrives, common signs of a gas leak, and the responsibilities of landlords in rented properties.
If You Suspect a Gas Leak: Immediate Steps
If you can smell gas — a sulphurous, rotten egg-like odour — or hear a hissing sound near a gas pipe or appliance, act immediately:
- Do not use any electrical switches — do not turn lights on or off, do not use any socket outlets, do not use a doorbell. A spark from an electrical switch can ignite gas in the air.
- Extinguish all naked flames — cigarettes, candles, gas cooker pilot lights (if you can do so without operating an electrical ignition).
- Do not use your mobile phone inside the property — step outside first before making any calls.
- Open doors and windows to ventilate the space as you leave.
- Turn off the gas supply at the emergency control valve (ECV) — this is typically located next to the gas meter. Turn the handle 90 degrees so it is perpendicular to the pipe (off position).
- Leave the property immediately and do not re-enter until it has been declared safe by a Gas Safe engineer.
- Call the National Gas Emergency Service: 0800 111 999 (available 24 hours, 365 days). This is operated by Cadent Gas (for most of London) and is a free call. The emergency response team will attend and make the supply safe.
Do not attempt to find or repair the leak yourself. Only a Gas Safe registered engineer may carry out work on gas installations. Re-entering a property with an active gas leak before it has been cleared by an engineer is extremely dangerous.
Common Signs of a Gas Leak
- A smell of sulphur or rotten eggs (the odorant added to natural gas to make it detectable)
- A hissing or whistling sound near a gas pipe, meter or appliance
- Visible damage to a gas pipe
- Dead or dying plants in a normally healthy area near external pipework (underground gas leaks can affect vegetation above the pipe run)
- An unexplained sudden increase in gas consumption on your meter
- Bubbling in puddles near external gas pipework (indicating underground leakage)
Note that carbon monoxide is odourless and colourless — it does not smell like gas. If you are concerned about carbon monoxide, the symptoms in occupants (headache, nausea, dizziness, confusion) are the primary indicator. Carbon monoxide alarms are the only reliable detection method. Both types of alarm — carbon monoxide detectors and natural gas detectors — are advisable in London properties with gas appliances.
After the Emergency Service Attends
The National Gas Emergency Service will attend to make the supply safe — this may involve capping a leaking pipe, condemning an appliance, or simply declaring the property safe if no leak is confirmed. They are not a repair service. Once they have made the supply safe and departed, a Gas Safe registered engineer must carry out any repair work before the gas supply can be reinstated.
If the engineer identifies the source of the leak as a pipe within the property, the repair is the responsibility of the property owner (or leaseholder-landlord in a block of flats). If the leak is traced to the supply pipe between the meter and the street main — the service pipe — the responsibility falls to Cadent Gas (or the relevant gas transporter for your area).
Landlord Responsibilities Following a Gas Leak
If the gas leak occurs in a rented property, the landlord has both immediate and ongoing responsibilities:
- Arrange emergency repair promptly. A property without a gas supply cannot be habitable in cold weather if the only heating source is gas — this implicates the landlord's obligations under the Landlord and Tenant Act 1985 and the Homes (Fitness for Human Habitation) Act 2018.
- Do not allow tenants to re-occupy until the supply has been reinstated and a new or updated Gas Safety Record has been issued.
- Notify your insurer if the leak caused damage to the property or a neighbouring property.
- Review the annual gas safety inspection schedule. A gas leak in a landlord property that is not covered by a current CP12 creates significant legal exposure. If the certificate was current, the leak may still lead to questions about whether the annual inspection process was thorough.
Gas Safety Equipment in London Properties
Under the Smoke and Carbon Monoxide Alarm (England) Regulations 2022 (effective 1 October 2022), landlords are required to fit at least one carbon monoxide alarm in any room used as living accommodation that contains a fixed combustion appliance — including gas boilers and gas fires. This is in addition to smoke alarm requirements. Natural gas detectors, while not yet legally mandated, are strongly advisable given that carbon monoxide alarms will not detect a gas leak from an unlit appliance or pipework.
Both types of detector should be tested regularly — monthly is the recommended interval — and replaced according to the manufacturer's guidelines, typically every five to ten years.
Frequently asked questions
What number do I call for a gas leak emergency in London?
Call the National Gas Emergency Service on 0800 111 999 — available 24 hours a day, 365 days a year. This is a free call and covers all of London. Do not call from inside the property; step outside first.
Can I turn off the gas at the meter if I suspect a leak?
Yes. Turning off the gas at the emergency control valve (ECV) next to the gas meter is one of the recommended immediate steps. Turn the handle 90 degrees so it sits perpendicular to the pipe. However, this does not substitute for calling the National Gas Emergency Service — call 0800 111 999 after leaving the property.
Does a gas leak smell? How can I tell if there is one?
Natural gas itself is odourless, but gas suppliers add a sulphurous odorant — described as smelling like rotten eggs — specifically to make leaks detectable by smell. A hissing sound near pipework, a sudden increase in gas consumption, or damage to nearby vegetation can also indicate a leak. Carbon monoxide, by contrast, has no smell — it requires a dedicated alarm to detect.
Who pays for gas leak repairs in a rented London property?
The cost of repairing a gas leak within the rented property — whether at an appliance or in the internal pipework — is the landlord's responsibility under Section 11 of the Landlord and Tenant Act 1985. If the leak is in the service pipe between the meter and the street main, Cadent Gas (or the relevant gas transporter) is responsible for the repair at no charge.