Carbon Monoxide (CO) – The Silent Killer

Carbon Monoxide (CO) is a silent killer, with around 50 deaths and hundreds of injuries recorded nationally every year.

What is Carbon Monoxide (CO)?

CO fumes are silent, highly poisonous fumes that are produced by the incomplete burning of fossil fuels (e.g. coal, gas, oil, wood). CO is difficult to detect because you cannot taste, see or smell it.

This can happen when appliances such as boilers, cookers, heaters, gas fires and solid fuel burners are faulty, have been incorrectly fitted, or not regularly serviced. It can also occur if flues, chimneys or vents that are blocked or poorly maintained.

What to do if you suspect CO poisoning?

  • Leave the property immediately.
  • If someone is showing signs of poisoning or has collapsed, get them outside, call 999 and ask for an ambulance.
  • If you suspect CO poisoning, always seek immediate medical advice. See your doctor or go to hospital – let them know that you suspect CO poisoning. They can do a blood or breath test to check.
  • Before you return to your home it is very important to call the 24 hour Gas Emergency Number on 0800 111 999 and tell them what has happened and receive safety advice (even if the suspected source of the CO is not a gas appliance).
  • Do not re-enter the home until the source of the CO has been addressed/fixed by a qualified professional.
  • You may need an engineer to inspect your appliances and flues to check that all is well.

If you believe there is a danger from gas, contact the Gas Emergency Helpline on 0800 111 999.

Where can this happen in the home?

CO can be produced by:

  • Blocked or poorly maintained chimneys or flues
  • Portable heaters using liquid petroleum gas (LPG)
  • Gas boilers and appliances including fires
  • Gas cookers or clay ovens
  • Car engines and generators
  • BBQs - charcoal or gas

If your home is a houseboat, CO can also be produced by:

  • Boat engines and generators
  • Wood and coal burners
  • Gas cookers or fridges
  • Car engines

Get a CO alarm to detect any leaks:

It's really important to fit a CO alarm in all rooms containing fuel burning appliances, ensuring that the alarm is able to be heard throughout your home. When sleeping, it is important that your alarm would wake you if it sounds. You therefore may wish to keep a CO alarm in the bedroom.

  • Get your CO alarm/s from a reputable DIY store or supermarket.
  • Only buy alarms that have been certified to British Standard EN50291 and have the British or European approval mark, such as the Kite mark.
  • If purchasing an alarm for a houseboat or caravan, please note that they need to comply with a different British standard: BS EN50291-2.
  • Follow the manufacturer’s instructions on how and where to fit.
  • Alarms purchased should be audible alarms, or hard of hearing alarms (avoid ‘colour change’ or ‘black spot’ indicator tools).
  • Alarms should be placed in any room that has a fuel burning appliance.
  • They will alert you if there is a presence of CO and allow you to escape.
  • Take a free-standing alarm with you when you go away on holiday - whether you are staying in a hotel, boat, tent or caravan.
  • If you or someone you care for uses telecare services, approach the supplier for linked-in smoke and CO detection.

Advice for landlords:

All landlords of private residential rental properties in England are required by law to install a carbon monoxide alarm in any room that contains a solid fuel burning appliance (e.g. coal or wood burning fires and stoves). The Government also ‘expect and encourage reputable landlords to cover all gas appliances’. Keep up to date with the regulations.

Advice for tenants:

You are responsible for testing the carbon monoxide alarms regularly during your tenancy and making sure they are working effectively (including arranging for the replacement of batteries or the alarms themselves with the landlord).

Prevent CO incidents:

Register and maintain your appliances:

If you are concerned about the safety of your boiler or any other appliance or having difficulty with your fuel bills, contact your energy supplier. They may have schemes or grants to help. Get more advice and information on what support is available.


Never take portable or disposable BBQs, grills or charcoal fuel burners into your home or any confined spaces such as a tent, houseboat or caravan.

Even if you have put out the fire, leave it outside and well away from the building or tent/caravan that you are staying in. An extinguished BBQ can continue to produce CO for many hours after it has been extinguished and remember, CO can travel through walls.

Keep your home or houseboat well ventilated.

Warning signs in your home:

Look out for:

  • Yellow instead of blue flames coming from the gas appliance or flames that are not fully formed (e.g. if the flame doesn’t go all the way around the ring).
  • Black, sooty marks on the front covers of gas fires
  • Sooty or yellow/brown stains on or around boilers, stoves or fires
  • Pilot lights frequently blowing out
  • Increased condensation on windows
  • An unfamiliar or burning smell when gas or oil appliances are on.
  • If you live on a houseboat, smelling or seeing smoke escaping into the cabin when your log burner or coal stove is on

Recognise the symptoms

Poisoning from CO can happen in a matter of minutes or over an extended period of time; it just depends on the amount of CO present.

The symptoms may only occur when you are near the source of the CO (e.g. in your home) and disappear or seem to get better when you are no longer near the source (e.g. leaving your home).

 Keep in mind that pets can also be affected by CO poisoning.

 Examples of high level CO exposure over a short period of time include:

  • Breathlessness and chest pain
  • Seizures
  • Racing heart beat
  • A loss or co-ordination
  • Vertigo
  • Feelings of being intoxicated and confusion
  • loss of consciousness

A slow build up of CO over a long period of time can lead to serious health problems such as:

  • Headache
  • Tiredness
  • Confusion
  • Dizzy spells
  • Stomach pain
  • Nausea and vomiting
  • Shortness of breath and difficulty breathing
  • Paralysis