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How to prevent and detect gas leaks

Gas leaks aren’t simply inconvenient, they can be dangerous too. Gas safety is something every household should take seriously. In this guide we equip you with the tools you need to detect gas leaks, understand why they happen, and take steps to rectify the problem before you put your home – and loved ones – at risk.
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Copper pipe showing gas leak

What are the signs and symptoms of a gas leak?

The first and most obvious sign of a gas leak is a sulphur-like odour that some have compared to rotten eggs. Other signs to look for include a hissing or whistling sound of gas escaping, bubbles, dust or cloud in standing water, and obvious signs of physical damage to pipes and hoses carrying your gas supply to your appliances and boiler.

As gas enters the air enclosed in your home, the amount of oxygen decreases. Look out for house plants suddenly dying, along with potential symptoms of carbon-monoxide poisoning, including feeling light-headed, dizzy and nauseous or suffering from a headache. These symptoms first tend to affect older people, children, pets and anyone suffering from respiratory diseases such as asthma, but everyone experiences them eventually.

If you feel any of these symptoms, open doors and windows to ventilate the house and get outside. If the symptoms suddenly fade, this confirms you’re likely to be suffering from carbon monoxide poisoning. 

If you remain unwell even after going out into the fresh air, contact your GP or hospital and tell them you suspect you’ve been exposed to a gas leak or carbon monoxide poisoning.

Note: gas leaks aren’t the only cause of carbon monoxide poisoning. Read our guide to spotting and dealing with carbon monoxide poisoning to find out more.

What causes a gas leak?

Gas leaks in the home are usually the result of poorly fitted, badly maintained or faulty appliances like boilers and cookers.

If your appliance is badly fitted, gas can escape – usually from the hose that carries the gas to your appliance or from around the seal. It may also be linked to a leak in the gas pipes delivering gas into your property. 

How to detect a gas leak

Aside from the smell of gas and other signs described above, your household appliances may also give off clear signs of a gas leak, even if you’ve yet to personally detect the effects.

You can obviously use your nose to try and sniff out the source of a leak, but it’s more important to ventilate your home first. If you suspect a particular appliance, stop moving and listen carefully for any hissing or whistling noises that may indicate a gas leaking from a confined space – such as a poorly fitted seal.

If your gas stove is currently on, another tell-tale sign of a leak is that it gives off a tired-looking orange or yellow flame instead of the usual blue one, indicating a lack of oxygen in the air. Switch it off immediately if this is the case.

Another similar indicator could come from a pilot light that refuses to stay lit. Also examine your appliance for signs of soot or any black or brown scorched areas.

Also look out for excessive condensation on the windows, or a musty smell in the air.

How to find gas leaks

If there’s a hissing or whistling noise, follow the sound carefully to see if you can safely discern its source (make sure the room is properly ventilated first, and that no electrical items are on). It’s possible you may be to trace it this way to the source – say the hose connecting the supply to your gas cooker, or a pipe leading to your boiler.

If you need to locate the exact source of a leak, you can perform a soapy water test. Add a teaspoon of washing-up liquid to around 250 millilitres (around 8 fluid ounces) of water. Apply it to where you suspect there’s a leak – if bubbles form, it indicates escaping gas. Note, this is primarily useful in confirming the location of a known gas leak; it is not a conclusive test for gas leaks in and of itself. 

Note: it’s more important to cut your gas supply as soon as possible (see below) than discover where a leak has occurred. Leave that to the experts.

What should I do if I smell gas?

Don’t dither – if you smell or detect gas in your home, act immediately. First, avoid smoking, burning any naked flames (such as candles or matches), or using any electrical devices – including switches, doorbells and mobile phones – as they could produce a spark that results in a gas explosion.

Second, you need to locate the mains gas control – which should be close to your meter. Turn this 90 degrees to shut off the supply. Note, if this is found in the cellar or basement of your home, and that’s where the smell of gas emanates from, don’t go down the stairs – you could quickly be overwhelmed; instead, move on to the next step.

Next, ventilate your home by opening windows and doors. This prevents the gas building up and – if you’ve shut off the gas supply – should ensure it dissipates harmlessly. If you’re unable to ventilate your home, get outside and into the fresh air to avoid carbon monoxide poisoning.

Once you have taken these steps and dealt with the immediate danger, it's time to call in the experts. The National Gas emergency number is 0800 111 999 – consider saving the number to your mobile and writing it down in an easily accessible location. Make the phone call from outside your property – particularly if you’re calling from your mobile (although the risk of it igniting the gas is small, it’s nevertheless a risk). 

Once you’ve called the number, make sure you or someone else is around to help the emergency engineer locate the leak and gain access to your home or property once they arrive.

Finally, if a fire breaks out, your first call should be 999 to the fire brigade.

How do I prevent gas leaks?

To prevent gas leaks, ensure all new gas boilers and appliances are installed and serviced by an accredited Gas Safe (previously CORGI) engineer. Also be wary around older or second-hand appliances, particularly if you’re just moving into a new property (renting or otherwise). 

Perform a visual inspection of any appliances for any signs of obvious wear and tear, and make sure your boiler receives an annual service from a Gas Safe engineer. Not only will you remain safe, you’ll keep your hot water and heating systems running efficiently.

If you’re not sure if your engineer is accredited, check the Gas Safe website or by asking them to show their registration card.

Carbon monoxide detectors

To avoid carbon monoxide poisoning, install an audible carbon monoxide alarm in your home - they look similar to smoke alarms and are readily available from DIY stores. Make sure they are installed in an open space like a hallway or in the kitchen, and be sure to test them regularly, checking the batteries and replacing them when the low warning appears.

What can happen if a gas leak isn't dealt with?

If left unchecked, a natural gas leak can lead to serious consequences. Unsafe appliances could result in fires, explosions and carbon monoxide poisoning. Over the past five years, there have been an average of 31 gas explosions a year, resulting in the deaths of at least 12 people, with hundreds more injured.

Read our dedicated guide for more gas safety tips.


How to prevent and detect gas leaks