Gas Fire Safety: Carbon monoxide, Servicing & Safety Checks

Gas fires are visually attractive and provide efficient heating.

But if they’re not maintained, or are poorly fitted, they can become a safety hazard.

This guide explains what these risks are, how to check your gas fire and how to recognise warning signs.

Gas fire risks

Modern gas fires are generally safe when correctly installed, serviced annually, and used as intended.

But they have four main potential safety hazards.

1. Carbon monoxide poisoning

Carbon monoxide (CO) is a toxic, invisible and odourless gas. It’s produced when a gas fire burns fuel incompletely, typically because of:

• Poor ventilation
• A flue blockage
• An appliance fault. 

It can reach dangerous concentrations before anyone notices the early symptoms, which include headaches, nausea, dizziness, lethargy, shortness of breath, and – importantly – confusion. 

Symptoms that improve when you leave the building are a strong warning sign. 

If you suspect CO exposure, get outside immediately, call 999, and don’t re-enter until an engineer has cleared the property.

Besides these symptoms, you might also notice visual warning signs on the appliance. These include:

• Flames burning yellow or orange instead of crisp blue
• Yellow-brown staining around the fire casing.

Does carbon monoxide rise or sink?

Carbon monoxide has almost the same density as air, so it doesn’t sink or rise. Instead, it spreads invisibly across the entire space. 

Someone asleep in a room with a CO leak can inhale a fatal dose without any sensation that prompts them to wake up and act.

This means detector height matters less than many people assume. Eye level, slightly above, and ceiling-mounted are all acceptable positions. Follow the manufacturer’s guidance and keep the detector away from corners and direct air vents.

2. Chimney blockages

When chimneys (or flues) become partially or fully blocked, waste gases accumulate in the room they were created in.

A partial blockage is particularly dangerous because it gives no obvious warning. The fire appears to work correctly while CO quietly builds up.

3. Contact burns

The glass front of a gas fire reaches temperatures exceeding 200°C during normal operation. At this temperature, touching it can cause severe burns.

It also stays dangerously hot for some time after switching off. The hazard is greatest for young children.

4. Fire risk

Gas fires can cause fires in some circumstances, such as if: 

• Combustible items (soft furnishings, curtains, rugs, etc.) are placed too close
• The glass front cracks and allows heat or flame to escape directly into the room
• A gas leak from a faulty connection accumulates and ignites.

Keep a perimeter of one metre around the fire at all times and don’t leave it running in an unoccupied room.

Making your gas fire safe

Have it installed by a Gas Safe registered engineer

Incorrect installation causes most gas fire accidents. Faulty gas pipe connections and poor positioning risk gas leaks, fires, and toxic fume buildup.

Never fit or move a gas fire yourself.

By law, only a qualified Gas Safe registered engineer can install gas appliances. So, before work begins, check the engineer’s registration at gassaferegister.co.uk. And ask to check their official Gas Safe ID card.

Service your gas fire every year

Annual servicing keeps your gas fire operating safely and efficiently. Regular maintenance prevents costly breakdowns and protects manufacturer warranties.

A standalone gas fire service generally costs between £60 and £100. Find vetted local engineers by searching gassaferegister.co.uk.

During an annual service, your engineer carries out key maintenance checks:

• Checking flue flow and clearing any chimney obstructions
• Checking operating pressure and gas heat input
• Cleaning internal burners, coals, and ignition components
• Testing flame supervision devices (safety valves that shut off gas if the pilot light goes out)
• Checking that ventilation openings meet the specific requirements for your fire model

Maintain good ventilation

Gas fires need a continuous supply of air to burn fuel safely and discharge combustion fumes outside.

A conventional flue fire (it draws air from the room and vents through a chimney) and a flueless fire (relies solely on room air) both require unobstructed room vents. And a balanced flue fire draws air directly from an outside wall pipe.

Never block, cover, or close air vents in a room with a gas fire. 

Obstructed ventilation starves the flame of oxygen and causes carbon monoxide to build up. 

If your room feels stuffy, smells unusual, or the flame turns yellow, turn off the fire and call the National Gas Emergency Helpline on 0800 111 999.

Install a carbon monoxide detector

Every room containing a gas fire must have an audible carbon monoxide alarm that meets British standard BS EN 50291. A detector alerts your household before toxic gas reaches fatal levels.

Mount your detector following the manufacturer’s instructions. Position it at eye level or slightly above, away from corners, drafts, and direct air vents. 

Ceiling placement is also safe. Check the alarm monthly by pressing the test button, and replace the unit before its expiry date.

Don’t sleep with it on

Never leave a gas fire burning overnight or whilst you are asleep. Unattended gas fires risk oxygen depletion, carbon monoxide buildup, and accidental fires caused by stray fabrics.

Always turn off your gas fire using the main appliance controls before going to bed.

Install a fireguard

Protect children and vulnerable family members by fitting a fireguard that complies with BS 8423 and attaches securely to the surrounding wall. 

Teach children to keep at least one metre away from the fire at all times, and never leave them in the room with the fire unattended.

How to turn off or extinguish a gas fire

Turn the fire off using the main appliance control knob or remote. Don’t use water on a gas fire, it can cause a dangerous flare-up. And don’t attempt to smother the flames.

If the fire does not respond to the controls, leave the room, close the door behind you, and call the National Gas Emergency Helpline on 0800 111 999. Do not attempt to disconnect the gas supply yourself.

Bio-ethanol fires: A separate but serious risk

Bio-ethanol fires are an alternative to traditional heating systems.

They burn liquid bio-ethanol fuel rather than gas and don’t require a flue or chimney, which makes them easy to install.

But the fuel itself is highly flammable, and refuelling mistakes can cause explosions.

The most important rule: Never refuel a bio-ethanol fire while it is lit or still hot.

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Residual heat in the burner can ignite fuel the moment it is poured in. The South Wales Fire and Rescue Service issued this warning after a couple in Penarth were left with serious burns when their bio-ethanol fireplace exploded on relighting. The fire engulfed their home within minutes.

To use a bio-ethanol fire safely:

• Never leave the fire running overnight or when leaving the room
• Always allow the burner to cool completely before refuelling
• Wipe up any fuel spills before relighting
• Never move the fire while the burner is lit
• Store fuel in a cool, dry place, away from direct sunlight and other heat sources
• Keep a CO detector in the same room. Bio-ethanol fires consume oxygen and can produce carbon monoxide in poorly ventilated spaces

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