What should I do if I smell gas in my home?

The smell itself is a warning added deliberately. Gas is naturally odourless, so a substance called mercaptan is added to make it detectable, giving it a potent sulphur-like smell similar to rotten eggs³. If that smell is present, the priority is ventilation and distance, not diagnosis. Do not operate electrical switches, do not use a naked flame, and do not stay in a cellar or basement where gas can be smelled¹.

What follows is the sequence the networks themselves set out, the rules on turning gas off at the meter, who attends and how they prove who they are, and why nobody restores a gas supply except a qualified person.

What to do immediately: the steps before you call

The order matters. Open doors and windows to let fresh air in, turn off the gas at the meter if it is safe to do so, and leave the property, calling the emergency line from outside². Guidance from Electricity North West, which runs the Extra Care register for priority households, puts the same sequence plainly: open your doors and windows, turn off gas at the meter unless the meter is in a cellar, do not use electric switches, and extinguish naked flames⁴. Cadent's own emergency advice adds the same prohibitions: avoid using switches, do not turn any power or light switches on or off, light no flames, and do not use appliances that could cause a spark⁵.

Appliances should be switched off before evacuating. Network guidance states: "We do recommend that you ensure your gas appliances are switched off before evacuating your property."⁶ That is a recommendation, not a condition of leaving, and it should never delay getting out.

If the smell is accompanied by symptoms, the response widens. Where someone has collapsed or is displaying severe symptoms, medical help comes first: call 999 or 112⁸. Carbon monoxide exposure produces the same first moves, open all doors and windows, move outside into fresh air, and call the Gas Emergency Service on 0800 111 999⁹.

The National Gas Emergency line: 0800 111 999, free and staffed 24/7

One number covers the whole of Great Britain. SGN publishes it as the National Gas Emergency Service on 0800 111 999¹, Northern Gas Networks gives the same number for a gas smell¹¹, and the industry guidance from the Energy Networks Association repeats it for anyone who smells gas¹². The National Energy Action home energy checklist calls it the 24-hour Gas Emergency Hotline on 0800 111 999¹³, and Smart Energy GB gives the same instruction to call the national gas emergency number immediately¹⁴.

The service is free to the caller. SGN states that "The National Gas Emergency Service is a free 24-hour helpline."¹ Northern Gas Networks confirms lines are open 24/7¹⁵. Wales & West Utilities describes its emergency number as free and available at any time, day or night, 365 days a year¹⁶.

There is no separate non-emergency number for a gas smell. The same line takes reports of a gas smell, low gas pressure and suspected carbon monoxide¹⁷. If the smell is faint or intermittent, say so when you call; the advisor decides what response is needed. Tell the advisors about any vulnerabilities or special circumstances that need to be known, including mobility, medical or communication needs¹.

Turning off the gas at the emergency control valve, and why you do not have to before evacuating

The emergency control valve sits by the gas meter. Where there is no label present, the emergency control handle is turned through 90 degrees to close the valve¹⁸. That is the valve the networks refer to when they say a householder would be asked to turn off the gas at the emergency control valve by the meter¹⁹.

Turning it off is advised where it is safe, but it is not a precondition of evacuating. The one clear exception is a meter in a cellar or basement: guidance says to turn off gas at the meter unless the meter is in a cellar, and separately warns against staying in a cellar or basement with a smell of gas⁴. In that case the correct action is to leave the space and call from outside.

For homes on LPG rather than mains gas, the shut-off points differ. Liquid Gas UK advises that no matter where you smell gas, you close the manual outlet valve on the cylinder or tank, turn off all appliances and the property's emergency valve, open doors and windows, avoid switching lights or electrical equipment on or off, call your supplier, dial 999 for the fire brigade and leave the premises¹⁹.

Who attends, how they identify themselves, and the free password scheme

An emergency engineer attends following a report to the national line. Cadent publishes a document for the visit that can be shared with a landlord, housing association or Gas Safe registered installer²⁰. That sharing route matters in rented homes, where the tenant may not be the person who arranges any follow-up work.

Identification is handled two ways. Networks offer a password scheme: Northern Gas Networks will "Offer, free of charge, to agree a password which can be used to help the customer identify the person attending."²¹ The Extra Care register used by Electricity North West works on the same principle, with the representative making a quick phone call to find out the password, prove their identity and keep the customer feeling safe²². Separately, Gas Safe registered engineers carry a hard copy card or show it on their phone, and that can be checked with Gas Safe if there is any doubt²³. Anyone registered to carry out gas work holds a Gas Safe ID card²⁴.

Households with additional needs can be recorded in advance. Northern Gas Networks runs a priority customer register²¹, and Ofgem has consulted on priority service research covering how such registers work²⁵. Being on a register does not change the emergency response, but it means the network knows about a vulnerability before it arrives.

Getting your supply restored: why a qualified person must do it

Once a gas supply has been turned off, it does not go back on at the householder's hand. Northern Gas Networks states that this "will have to be done by an appropriate qualified person"⁶, and the flood guidance from Cadent is blunter still: "please do not try to turn your gas supply back on again"⁷. The same rule appears in Northern Gas Networks' flood advice, which says restoration must be done by an appropriate qualified person⁶.

Restoring supply is not the end of the matter. After an emergency visit, further repairs to appliances or pipework may need a Gas Safe registered engineer²⁶. SGN's carbon monoxide guidance is that a Gas Safe registered engineer should always be used to fit, fix and check appliances²⁷. Registration to carry out gas work requires proof of the necessary qualifications and experience²⁸.

For a household, this is the point where independence runs out. A gas connection is a shared, regulated system: the pipe to the meter belongs to the network, the meter to the supplier, and the work on either is reserved to registered people. A home can control its appliances, its ventilation and its response to a smell, and nothing beyond that.

Which network covers your home: Northern Gas Networks, Wales & West Utilities and the rest of Great Britain

Great Britain's gas distribution networks are owned by four groups: Cadent Gas Ltd, Northern Gas Networks Limited, SGN, and Wales & West Utilities Limited²⁹. Which one covers a home depends on where it is.

Northern Gas Networks runs the pipes across the North of England³⁰, and is listed as the gas transporter for Northern England³¹. Wales & West Utilities covers the whole of Wales and the South West of England³², and its network plans cover Wales and the South West³³. SGN covers Scotland and southern England³⁴. Cadent covers the East of England and other regions²⁹.

The network matters for connections and alterations rather than for emergencies, because the emergency number is national. Wales & West Utilities, for example, handles requests for a new gas supply, changes to an existing supply such as moving a pipe for an extension, altering the location of an existing meter, and disconnecting a supply that is no longer needed³². Northern Gas Networks takes applications for new connections¹⁶. Before any excavation, the Dial Before You Dig service provides scaled plans of the network³³.

Northern Ireland sits outside this structure, with its own gas network arrangements. For a household there, the emergency response and the network operator differ from Great Britain, and the number to call should be confirmed locally.

What if I smell gas after a flood?

Flooding changes the sequence slightly. If the property has been flooded and it is safe to do so, turn off the gas supply at the gas meter⁷. Then leave and call the emergency line. Do not attempt to restore the supply afterwards: the same rule applies, that restoration must be done by an appropriate qualified person⁶.

Contact the gas emergency line if you can smell gas, experience poor pressure or have no gas after flood water has left the home⁶. That covers the period after the water has gone, when a smell or a loss of pressure can still indicate damage to pipework or the meter installation.

Where a petrol generator is used during or after flooding, ventilation is critical. Guidance warns that it is vital to ensure there is adequate ventilation to prevent potential exposure to carbon monoxide¹⁸. Generators are a common feature of flood recovery, and they carry their own risk separate from the gas supply.