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Gas

How Do You Know If You Have a Gas Leak?

Published 17 February 2025 · Updated 9 October 2026 · 2 minute read

A white carbon monoxide alarm fitted on a wall
In this guide

Gas leaks are uncommon, but they are serious. Knowing the signs, and what to do, takes a minute to learn and could matter a great deal.

The signs

  • A smell. Natural gas has no smell of its own, so a smell is added to make leaks noticeable. It is often described as rotten eggs or sulphur.
  • A hissing or whistling sound near a gas pipe or appliance.
  • A gas appliance behaving oddly. A hob flame that is yellow or orange rather than blue is a sign something is wrong.

What to do if you smell gas

  1. Call 0800 111 999. Do it from outside, or a neighbour's house, if you can.
  2. Open doors and windows to let the gas out.
  3. Turn off the gas at the meter if you know where it is and it is safe to reach.
  4. Do not use naked flames, and do not smoke.
  5. Do not turn electrical switches on or off. A small spark can ignite gas.
  6. Leave the property if the smell is strong, and keep other people away.
  7. Do not go back inside until you have been told it is safe.

After the emergency service has made the situation safe, any repair has to be done by a Gas Safe registered engineer. Do not use the appliance again until it has been checked.

Gas leak versus carbon monoxide

These are two different dangers and people often mix them up.

A gas leak is unburnt gas escaping. You can usually smell it.

Carbon monoxide is a poisonous gas produced when fuel burns without enough air. It has no smell, colour or taste. Warning signs include headaches, dizziness, nausea, tiredness and confusion, often easing when you leave the house. Candle-like yellow flames, soot marks around an appliance and a pilot light that keeps blowing out can also be clues.

Fit a carbon monoxide alarm that meets the British Standard, test it regularly, and if it sounds, open the windows, leave the house and call 0800 111 999.

How to reduce the risk

  • Service your appliances every year with a Gas Safe registered engineer. See how often a boiler should be serviced.
  • Use only registered engineers for gas work. Ask to see their Gas Safe ID card.
  • Keep vents and flues clear.
  • Replace old, damaged or unsafe appliances.
  • Landlords must arrange an annual gas safety check. Our gas services include landlord gas safety certificates.

When to call us

For emergency gas work after you have called the emergency service, or for a safety check on a gas appliance, contact us. We are Gas Safe registered and offer emergency callouts 24/7 across North Norfolk, Hertfordshire and Bedfordshire.

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