Does a Rotten Eggs Smell or Cabbage Smell Mean a Gas Leak?

James Elston
Written by James Elston
Updated on 26th February 2024
Posted on 17th January 2024
Topic: Boiler Advice
rotten eggs gas leak

If you suspect a gas leak call 0800 111 999 immediately

Gas leaks can be hazardous, potentially leading to fires, explosions, and health issues. One ultra-important safety measure is to be able to recognise the signs of a gas leak promptly.

But what exactly does a gas leak smell like? In this article, we will explore the distinctive odour of gas leaks, why it smells the way it does, and what actions you should take if you suspect a gas leak.

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Why does a rotten egg smell mean a gas leak?

Natural gas, which is commonly used in homes for heating and cooking, is odourless and colourless.

However, for safety reasons, a strong odorant called “mercaptan” is added to natural gas before it reaches your home.

Mercaptan gives natural gas a distinct and unpleasant smell.

If your boiler smells like cabbage, it could indicate a potential issue with your heating system that needs attention. The smell of cabbage or any unusual odour coming from a boiler is not normal and should be investigated.

Several factors could be responsible for such a smell including:

A smell resembling cabbage could be associated with a gas leak. Natural gas is odourless, but for the same reasons as above, the chemical called mercaptan is added to it to give it a distinct odour, often described as “rotten cabbage” or “sulfur-like.”

If you detect this smell, it’s essential to turn off the gas supply immediately, open windows for ventilation, and contact a professional to check for a gas leak.

If your boiler is leaking water then this isn’t as dangerous but could lead to more problems. Ensure you call a Gas Safe engineer to fix it as soon as possible.

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Burner Issues

A malfunctioning burner in your boiler can produce unusual smells, it will also likely cause others problems such as no hot water coming from your boiler or to your central heating system.

If it’s not burning fuel properly, it might emit odours that resemble cabbage or other unpleasant scents. This could be due to a dirty or clogged burner or a problem with the combustion process.

If you have an old boiler, it may be time to consider a new boiler replacement too. If you need a boiler emergency installation, then you can get one fitted as soon as the next day with Boiler Central. Make sure that you get the gas leak sorted first though!

Why Does Mercaptan Smell Like It Does?

Added to the gas supply, mercaptan is often described as having a sulfur or rotten egg-like odour. It’s pungent and easily recognisable. The reason for adding such a distinctive odour is to ensure that people can quickly detect gas leaks, even in small quantities.

The odour of mercaptan is intentional and serves as a safety feature. Here’s why:

  • Early Detection: The strong and unpleasant smell of mercaptan allows people to detect even minor gas leaks promptly.
  • Safety: It is high priority for people to be aware of gas leaks because natural gas is highly flammable. Early detection can prevent accidents and disasters.
  • Health Concerns: Inhaling natural gas can lead to health issues, such as nausea, dizziness, and headaches. The odour helps people avoid exposure to these health risks.

Did you know that you can’t smell a carbon monoxide leak? See what to do if your carbon monoxide detector is beeping here.

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Identifying a Gas Leak

Now that you know what a gas leak smells like, it’s essential to be able to identify one:

Signs of a Gas Leak

  • Rotten Egg Smell or Rotten Cabbage Smell: As mentioned earlier, a gas leak often smells like rotten eggs, rotten cabbage or sulfur.
  • Hissing Sound: Sometimes, you may hear a hissing or whistling sound from your boiler or near a gas line.
  • Dead or Dying Plants: If your indoor plants suddenly start wilting or dying without an apparent reason, it could be a sign of a gas leak.
  • Bubbles in Water: If there are unusual bubbles in standing water around your home, it might indicate a gas leak underground.
  • Physical Symptoms: Experiencing symptoms like nausea, dizziness, or breathing difficulties when you’re at home but feel better when you’re away may be a sign of a gas leak.

What to Do if You Smell Gas

If you suspect a gas leak call 0800 111 999 immediately – here are the other steps you should take immediately:

Immediate Actions

  1. Evacuate: Leave your home or the area where you suspect the gas leak immediately. Do not use any electrical devices, as they can spark and ignite the gas.
  2. Do Not Use Flames: Avoid lighting matches, candles, or any open flames.
  3. Do Not Use Electrical Devices: Do not use light switches, phones, or any other electrical appliances in the vicinity of the suspected leak.
  4. Ventilate: If it’s safe to do so, open windows and doors to help dissipate the gas.
  5. Call for Help: Contact your gas company’s emergency line and report the leak. They will send a technician to assess and repair the issue.


Understanding what a gas leak smells like is one of the first things you should learn for your safety and the safety of those around you. The odour of rotten eggs or sulfur, caused by the addition of mercaptan to natural gas, is a distinct warning sign.

If you ever detect this smell or suspect a gas leak, follow the safety guidelines mentioned above and seek immediate assistance from your gas company.

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Is natural gas always odourless?

No, natural gas is odourless by itself, but an odorant called mercaptan is added to it to give it a distinctive and unpleasant smell for safety reasons.

Carbon monoxide on the other hand is odorlous and can kill, hence why it is so important to have a carbon monoxide detector.

Can a gas leak occur outdoors?

Yes, gas leaks can occur both indoors and outdoors. It’s essential to be vigilant and follow safety procedures in both settings.

How long does the odour of a gas leak last?

The odor of a gas leak can linger for a while even after the leak is fixed. It’s essential to continue taking precautions until the smell dissipates entirely.

Are gas leaks common?

Gas leaks can occur, but they are relatively rare. Regular boiler servicing and maintenance and prompt detection can help prevent them.

Can I use my phone to call for help if I suspect a gas leak?

No, it’s not safe to use your phone near a suspected gas leak. Leave the area and use a phone at a safe distance to call for assistance.

Written by
James Elston
James Elston Director Of Boiler Central
Posted on: 17th January 2024
Topic: Boiler Advice

James Elston is our resident boiler replacement and heating expert here at Boiler Central. With over 20 years experience in the boiler installation industry, James ensures that he knows everything there is about our Gas Safe boiler installations, energy saving and home heating solutions. This can be from simply procuring the latest best combi boilers, to reviewing and ensuring that Boiler Central maintains the highest standards across our boiler installation company.

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