Carbon Monoxide(CO)

What is Carbon Monoxide (CO)?

Carbon Monoxide fumes are silent, highly poisonous fumes that are produced by the incomplete burning of fossil fuels. 

This can happen when gas appliances such as cookers, heaters, gas fires and solid fuel burners have been incorrectly fitted, or poorly maintained.  It can also occur if flues, chimneys or vents have faults/blockages. 


What are the symptoms of Carbon Monoxide poisoning?

You can't taste, see or smell CO fumes, but it can kill in minutes.  It's vital to know the symptoms of poisoning – if you don't have an alarm, it may be your only warning. 

CO poisoning symptoms:

  • Headaches

  • Dizziness

  • Nausea or vomiting

  • Breathlessness

  • Collapse

  • Loss of consciousness


These symptoms also apply to your pets – so keep an eye on them too.  It's also really important to spend a few pounds on a Carbon Monoxide alarm. Poisoning symptoms can easily be confused with just feeling unwell, which is why CO poisoning is so dangerous, and so often missed.


Signs that you, or a neighbour may have a Carbon Monoxide leak

  • Symptoms only occur when you are in your home and disappear or get better when you leave.

  • Others in your home are experiencing similar symptoms – including your pets.

  • Black, sooty marks on the front covers of gas fires.

  • Sooty, yellow or brown stains on or around boilers or stoves. 

  • Yellow instead of blue flames coming from gas appliances or flames are not fully formed – for instance, if the flame isn’t all the way round on a gas hob burner.

  • If you get any symptoms when appliances are in use. For example, when the boiler is on.

  • You notice increased condensation on the windows.

  • Pilot lights that frequently blow out.


Did you know? 

Carbon Monoxide can leak in through the fabric of your home from somewhere else in your block, house or terrace?  Get – and use – a CO alarm to be safe.b


What to do if you suspect Carbon Monoxide poisoning or if your CO alarm sounds

  • Open doors and windows to ventilate your home if possible.

  • If you are able to do so safely, switch off your appliances.

  • Get outside into the fresh air quickly.

  • If someone is showing signs of poisoning or has collapsed, get them outside, call 999 and ask for an ambulance.

  • If you suspect poisoning, always seek immediate medical advice. See your doctor or go to hospital – let them know that you suspect CO poisoning, they can do can do a blood or breath test to check.

  • Before you return to your home it is very important to call the gas emergency number on 0800 111 999 and tell them what has happened.

  • You may need an engineer to inspect your appliances and flues to check that all is well. 


Exposure to Carbon Monoxide can cause longer term problems – find out more on NHS Direct. You can learn more about CO poisoning on the Health and Safety Executive website. If you believe there is danger from gas contact the Gas Emergency Helpline on 0800 111 999.