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Quick answer
A gas hob or natural gas fire burning correctly produces a crisp blue flame. A lazy yellow or orange flame, soot marks or a flame that lifts or flickers unusually can indicate incomplete combustion, which can produce carbon monoxide. Some decorative fires are designed to burn with yellow flames, so check the manufacturer’s information. For hobs and most appliances, a persistent yellow flame means stop using it and have it checked by a Gas Safe engineer.
Key takeaways
- A normal gas flame on a hob is blue with a small, well-defined inner cone.
- Persistent yellow or orange flames suggest incomplete combustion.
- Incomplete combustion can produce carbon monoxide, which you cannot see or smell.
- Soot marks around a hob, fire or boiler are a warning sign.
- Some decorative fuel-effect fires burn yellow by design.
What a healthy flame looks like
A correctly adjusted gas burner mixes the right amount of air with gas. The flame is blue, steady and sits on the burner. Occasional flickers of orange can come from dust or cooking residue in the air, which is normal.
Causes of a yellow flame
- Blocked burner ports from spills and food residue on hobs.
- Burner caps misaligned after cleaning.
- Poor air supply or blocked ventilation.
- Incorrect gas pressure or appliance fault.
- Blocked or faulty flue on fires and boilers.
Cleaning hob burners safely
With the hob off and cool, remove burner caps, clean them according to the manufacturer’s instructions, dry them thoroughly and refit them correctly. If the flame is still yellow afterwards, stop using the hob and get it checked.
Warning signs of carbon monoxide
- Yellow or orange flames where they should be blue.
- Soot or staining on or around appliances.
- Excess condensation in the room.
- A pilot light that keeps going out.
- Symptoms such as headaches, dizziness, nausea and tiredness that improve when away from home.
See carbon monoxide poisoning symptoms and carbon monoxide alarms and your boiler.
What to do
- Turn the appliance off.
- Open windows and ventilate.
- If anyone feels unwell, get fresh air and seek medical advice.
- If you suspect CO or smell gas, call 0800 111 999.
- Have the appliance checked by a Gas Safe engineer before using it again.
Gas fires and cookers need servicing too
People often service the boiler but forget the fire and cooker. See gas fire servicing and safety and gas cooker safety and servicing.
Book with Gasmaster
Worried about a yellow flame? Gasmaster Plumbing & Heating, Gas Safe registered (220932), checks hobs, fires and boilers across Stoke-on-Trent, Newcastle-under-Lyme and Biddulph. See our Gas Safe engineers.
Frequently asked questions
Is a yellow flame on my gas hob dangerous?
A persistent yellow flame suggests incomplete combustion and should be checked. Stop using it until it has been inspected.
Can a dirty hob cause a yellow flame?
Yes. Blocked burner ports and misaligned caps are common causes.
Should my gas fire have a yellow flame?
Some decorative fires are designed to. Check the manufacturer’s information; if unsure, get it checked.
Sources
- Gas Safe Register, carbon monoxide advice (gassaferegister.co.uk)
- Health and Safety Executive, carbon monoxide guidance (hse.gov.uk)
- NHS, carbon monoxide poisoning (nhs.uk)
Related services
Abdul runs Gasmaster Plumbing & Heating and has worked on boilers, heating and gas appliances across Stoke-on-Trent since 2005. He is Gas Safe registered (reg. 220932), and these articles come from his day to day work in homes and businesses across Staffordshire, Cheshire and Derbyshire.
