About Carbon Monoxide (CO)


What are the symptoms of CO poisoning?

It’s worth remembering some symptoms of CO poisoning are similar to viral infections or tiredness, so try not to panic. However, call your doctor if you experience the following:

  • Headaches
  • Nausea or feeling sick
  • Breathlessness
  • Dizziness
  • Collapse
  • Loss of consciousness.

If you suspect carbon monoxide poisoning call immediately on

0800 111 999*

Initial stage includes:

  • Flu like symptoms, mild headaches, dizziness, weakness, nausea, confusion and increased heart rate.

Second stage includes:

  • Conscious but confused, disoriented, and movement difficulties due to extreme weakness.

Third stage includes:

  • Unconscious, convulsions, loss of muscle control, slow breathing.

Effects will vary for different individuals depending on the level and duration of exposure, body size and physical condition.

If your symptoms reduce or disappear completely when you’re out of the house, it might be carbon monoxide poisoning. See your doctor if you have any health concerns, or dial 999 in an emergency.


What are the signs of CO? Look for these things

If you spot any of the signs below, it doesn’t definitely mean that there is a release of CO, but it’s better to be safe than sorry.

  • Gas flame appears ‘floppy’ and burns orange or yellow rather than mostly blue
  • Pilot light frequently blows out
  • There is soot or yellow-brown staining on or around an appliance
  • You see or smell smoke or have excessive condensation in the room where you have a gas appliance.

If you’re concerned about any of the above, call the National Gas Emergency Service on 0800 111 999*

Installing a CO alarm

  • There should be an audible CO detector in every room with a fuel-burning appliance eg a boiler, cooker or fire. CO detectors can be used for any kind of fossil fuel – gas, oil, coal or wood.
  • The detector should be installed in accordance with the manufacturer’s instructions. Generally, this will be at least one metre away from the appliance, and no more than three metres away.
  • The detector should be positioned at least five feet off the ground, and preferably at  ‘top-of-door’ height.
  • CO detectors need to be installed where they can be heard.

​3 steps to staying safe

Step 1

Carbon monoxide safety tip 1

Identify the danger

Tip Know the signs and the symptoms to look out for

Step 2

Engineer showing his ID badge

Test your appliances

Tip Have your appliances serviced by a Gas Safe registered engineer every year

Step 3

Carbon monoxide safety tip 3

Install a CO alarm

Tip Fit an audible alarm in your home

What is carbon monoxide?

Carbon Monoxide (CO) is a colourless, odourless and tasteless gas, so it’s difficult to detect. It’s produced when fuels including gas, oil, coal or wood don’t burn properly due to:

  • an incorrectly fitted gas appliance
  • a poorly maintained gas appliance
  • a blocked flue, chimney or vent
  • a disposable or gas BBQ that’s not properly extinguished.

Gas appliances which can cause CO include:

  • cookers
  • fires
  • free-standing heaters
  • boilers and water heaters.


Suspect CO?

  • Open all doors and windows
  • Move outside into fresh air
  • Call the Gas Emergency Service on:
0800 111 999*

If someone has collapsed or is displaying severe symptoms, seek medical help by calling 999 or 112.

CO Safety If you suspect CO call:

24-hour national gas emergency:
0800 111 999

Gas emergency minicom:
0800 371 787

Solid fuel advice:
0845 6014 406

Health & Safety CO advice line:
0800 300 363

OFTEC oil-fired appliance advice:
0845 6585 080

Gas Safe Register information:
0800 408 5500