Carbon monoxide/gas

Carbon monoxide

Carbon monoxide (CO) is a colourless, odourless, tasteless, poisonous gas produced by incomplete burning of carbon-based fuels, including gas, oil, wood and coal.

Carbon-based fuels are safe to use. It is only when the fuel does not burn properly that excess CO is produced, and it is poisonous. When CO enters the body it prevents the blood from bringing oxygen to cells, tissues, and organs.

You can’t see it, taste it or smell it, but CO can kill quickly without warning. According to HSE statistics, every year around seven people die from CO poisoning caused by gas appliances and flues that have not been properly installed, maintained or that are poorly ventilated. Levels that do not kill can cause serious harm to health if breathed in over a long period. In extreme cases, paralysis and brain damage can be caused as a result of prolonged exposure to CO. Increasing public understanding of the risks of CO poisoning and taking sensible precautions could dramatically reduce this risk.

There are signs that you can look out for which indicate incomplete combustion is occurring and may result in the production of CO:

  • Yellow or orange rather than blue flames (except fuel-effect fires or flueless appliances which display this colour flame).

  • Soot or yellow/brown staining around or on appliances.

  • Pilot lights that frequently blow out.

  • Increased condensation inside windows.

People suffering from carbon monoxide poisoning should get fresh air immediately, open doors and windows, turn off gas appliances or extinguish other sources, leave the house and see a doctor.

There are a number of simple steps that gas consumers can take to keep themselves safe.

Carbon monoxide can be produced by any combustion appliance, including those that burn fossil fuels e.g. oil, wood and coal. If you have one of these appliances you should make sure that it is regularly serviced and maintained by a competent person, and the chimney is regularly swept.

Carbon monoxide alarms

Carbon monoxide (CO) alarms protect residents by giving an early warning when the poisonous gas is detected in the home. Installing a CO alarm is a simple DIY task, with most detectors only requiring a couple of screws, while some are free-standing and require no installation.

Ideally the alarms should be installed next to potential sources of CO in the premises and in sleeping areas. Advice from The Gas Safety Charity is, if you are installing the alarm in the same room as the appliance, make sure it is between one and three metres horizontally from the appliance. Avoid putting them too close to windows or air vents.


September is the start of the heating season and many people will be turning on their boilers.  We rely on our gas boilers, cookers and fires to keep warm, have hot baths and showers and cook hot meals.

It’s crucial that you get your appliances checked every year by a Gas Safe registered engineer to be assured they are working safely and efficiently, and to protect against the dangers of unsafe gas appliances such as fires, leaks, explosions and carbon monoxide (CO) poisoning.

Warning signs that gas appliances are not working properly, include:  lazy yellow flames instead of crisp blue ones, black marks or stains on or around the appliance and too much condensation in the room.

Gas safe registered engineers

To get your gas appliances safety checked each year, please contact a Gas Safe registered engineer in your area:

Find a Gas Safe registered engineer (opens in new window)  or call the free helpline on 0800 408 5500

Last updated: Wednesday, 26 July 2023