James Elston

Published April 9, 2024

If there is a smell of rotten egg coming from your boiler? This may be an indicator of a gas leak and you must act on it immediately.

In this article, Eco Happy will guide you on how to deal with gas leaks. We’ll cover everything from the steps you can follow to deal with the leak to how to prevent future leakage issues. Let’s take a look!

7 Steps To Take When You Suspect A Gas Leak

Once you smell gas you need to act fast, starting with step 1 below.

1. Extinguish open flames and do not operate electrical appliances

Your first course of action is to make sure there are no naked flames that could cause a gas fire.

Do not turn appliances or switches on or off. It could cause a spark that may cause an ignition.

2. Isolate where the leak is coming from

It may be difficult to pinpoint the exact source of a leak but you can follow these steps:


Determine where you smell gas the strongest. There may be a gas smell close to your boiler, but the gas leak itself may be along pipework away from the boiler unit. The smell of gas could also be coming from faulty appliances. 


Listen out for any whistling or gurgling sounds around your boiler system that could indicate leaking gas. A gas leak can have a variety of causes, some of which will result in leakage around the sealed parts of your boiler.

Do the same test around any other gas appliances so you can rule out if they are the cause of the smell. 


Check around your boiler, gas pipework and gas appliances for any discoloured or dead plants which is a potential sign of a gas leak.

3. Ventilate

Your next step is to open windows and all the doors to clear out the gas from your home and let fresh air come in. This will remove the risk of combustion. It will also prevent you from being overcome by gas, which can make you fall unconscious and unable to deal with the leak.

4. Turn off the gas supply

Your next step is to locate the main gas valve and switch it off to prevent further gas leakage from your boiler.

You will find it near or in your gas meter box, which will be near the boiler, under the kitchen sink or outside on the perimeter of your property. If it is a wheel-type valve, turn it clockwise to switch it off. If it is a lever-type valve, turn it until it is perpendicular to the gas pipe. 

5. Evacuate

Next, you must evacuate any occupants from your home. Remember to take your mobile phone with you as you will need it to contact the National Gas Emergency Helpline. Notify your neighbours of the gas leaks as well.

6. Call the National Gas Emergency Helpline

The next and most important step: You must call the National Gas Emergency Helpline on 0800 111 999 to report the leak.

If you don’t have access to a mobile phone, use your neighbour’s phone.

What happens when I call the National Gas Emergency Line?

When you call the National Emergency Line, you will be asked a series of questions, including your address and any details on the gas leaks. This will include where you can smell gas and what gas appliances you own. They will then send a technician to your property who will make sure the gas supply is shut and there is no more gas escaping. 

They will not fix any serious issues but they will make sure your property is safe and perform any possible temporary repairs. You will be able to return to your home once they have completed their work. 

7. Arrange for a Gas Safe engineer

Only registered gas engineers can fix serious gas-related problems with your boiler and its pipework. You will need to call and arrange for a Gas Safe registered engineer yourself. They will come to your property and assess the situation.

How Do I Know When a Gas Leak Is an Emergency?

Natural gas poses extreme health risks. As soon as you can smell that distinct sulphur odour, it already means there is an emergency. 

Additionally, if you hear your carbon monoxide alarm sound, it is also an emergency. Carbon monoxide is a poisonous gas that is colourless and odourless, so it won’t be detected even if you are looking for unusual boiler smells.

Physical symptoms of natural gas exposure

Below are some of the symptoms you may experience due to a gas leak.

  • Headaches, dizziness and light-headedness
  • Extreme fatigue and loss of consciousness
  • Vomiting and nausea
  • Difficulty breathing

If you are experiencing these symptoms, your gas leak is serious. Follow our 7 steps to assess and address the leak.

How Do I Prevent Gas Leaks?

One way to prevent a gas leak is to have a gas boiler alternative installed.

However, there are a couple of other ways you can prevent a gas leak:

Annual service

Ensure that your boiler is serviced annually. This will prevent problems that could lead to a gas leak. A Gas Safe engineer will also be able to detect any minor leaks and repair them before they turn into major problems.

Maintain your CO alarm

One of the best ways to spot a carbon monoxide leak early is with a functioning carbon monoxide alarm. You should change the device’s battery at least once a year and test that it’s functioning properly at least once a month.

Only use Gas Safe engineers

Always use a qualified Gas Safe registered engineer to perform repairs or installations. This way you know you won’t risk any shoddy workmanship that could lead to real problems.


Why does my heating system smell like gas?

Heating systems and radiators that smell like rotten eggs are quite a common problem in rural areas that use well water. The culprit is bacteria in the water that produces hydrogen sulphide, the same compound that is put in natural gas to give it its distinct smell. Bacterial colonies can also cause boiler smells.

Bacteria can be found within your boiler water system, or in slimy layers on the exterior. Get a plumber or boiler technician to treat your water and kill any bacteria that could cause the sulphur smell. Treatment generally involves adding chemicals to the boiler water.

Why do I smell gas when my boiler fires up

It is normal to smell gas when a combi boiler starts up. This is true even of a new boiler. The smell should quickly disappear though. If it does not, this may be a sign of a gas leak. Don’t just write it off as normal boiler smells. Rather be safe and follow our 7 steps listed above.

Unusual smells coming from your boiler during startup should always be investigated. Suspicious boiler smells can include a rotten egg smell but also burning fabric or melted plastic. Burning smells can be caused by shorts on your electrical circuits or collected dust touching the heat exchanger or heating elements.


You must take any signs of a boiler gas leak seriously. It means something is not as it should be. Strange smells are not part of normal boiler wear and tear. Follow our 7 simple steps to address the leak and contact theNational Gas Emergency Helpline as soon as possible.

If you want to replace your boiler or move away from a gas boiler, you can contact Eco Happy or use our quote comparison service. Find the best local heating specialist to get a great quality boiler at a great price.

James Elston

Boiler Expert

James Elston is the top boiler replacement and heating expert at Eco Happy. He has over 20 years of experience in the industry, focusing on Gas Safe boiler installations and offering home-heating and energy-saving solutions to homeowners across the UK. From sourcing the most energy-efficient combi boiler to providing specialist heating advice, James ensures that Eco Happy maintains the highest standards and best customer service.

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