• Gas Safe Register

Carbon monoxide poisoning – What are the symptoms?

Updated: Nov 29, 2019


You can't see, taste or smell it but it can be deadly

What is CO poisoning?

Unsafe gas appliances can produce a highly poisonous gas called carbon monoxide (CO). It can cause death as well as serious long term health problems such as brain damage.

CO is produced by the incomplete burning of natural gas or liquefied petroleum gas (LPG). This happens when a gas appliance has been incorrectly fitted, badly repaired or poorly maintained. It can also occur if flues, chimneys or vents are blocked.

Oil and solid fuels such as coal, wood, petrol and oil can also produce carbon monoxide.

CO poisoning occurs when you breathe in the gas and it replaces oxygen in your bloodstream. Without oxygen, your body tissue and cells die. Even small amounts of the gas can cause CO poisoning, and long term effects can include paralysis and brain damage.

Remember the six main symptoms to look out for:

  1. headaches

  2. dizziness

  3. nausea

  4. breathlessness

  5. collapse

  6. loss of consciousness


Being aware of the symptoms could save your life

CO symptoms are similar to those of flu, food poisoning, viral infections and fatigue. That’s why it’s quite common for people to mistake this very dangerous poisoning for something else. Other signs that could point to CO poisoning:

  • Your symptoms only occur when you are at home and seem to disappear when you leave home.

  • Others in your household (including pets) are experiencing similar symptoms and they appear at a similar time.

What to do if you suspect CO poisoning

  • Get fresh air immediately. Open doors and windows, turn off gas appliances and leave the house.

  • See your doctor immediately or go to hospital - let them know that you suspect CO poisoning. They can do a blood or breath test to check.

  • If you think there is an immediate danger, call the Gas Emergency Helpline on 0800 111 999.

  • Ask a Gas Safe registered engineer to inspect your gas appliances and flues to see if there is a dangerous problem.

To find engineers who are qualified to investigate the presence of fumes, you can visit our Check a Business page. Enter your postcode and select either Domestic or Commercial Appliances and press ‘Find’. Under the ‘Select appliance type’ tab chose ‘Fumes Investigation’. Remember to click ‘Find’ again to see the updated results.

The warning signs of a CO leak

Any of the following could be a sign of CO in your home:

  • Flames of a lazy yellow or orange colour on your gas hob, rather than being a crisp blue;

  • Dar