Skip to content

Carbon monoxide

What is carbon monoxide?

Carbon monoxide is a highly poisonous gas it is often referred to as the ‘silent killer’ because it has no taste, smell or colour, meaning it can be easily inhaled without somebody realising.

When carbon monoxide is breathed in, it starves the body of oxygen. High levels can kill within minutes, but it can also cause a range of non-fatal health problems, ranging from headaches and drowsiness through to lasting brain and nervous system damage.

Why should people be alarmed?

Despite the dangers, studies have shown that fewer than one in ten homes have a carbon monoxide alarm.* An audible carbon monoxide alarm is the only effective way for people to protect themselves and their families.

Young children and elderly people are particularly at risk from carbon monoxide poisoning because their bodies are less able to withstand the effects. Women should also be aware that if they don’t have an alarm and are pregnant they could be putting their unborn child at risk.

How many people are affected?

According to the Department of Health, more than 40 people in England and Wales die each year from carbon monoxide poisoning, and thousands more are treated in hospital. It is likely many more victims go unrecognised because the early symptoms can easily be mistaken for common illnesses such as flu or food poisoning.

What are the causes of carbon monoxide poisoning?

Carbon monoxide is produced when fuels such as gas, oil, charcoal, coal and wood do not burn fully. The most common cause of this is when a household fuel-burning appliance, such as a boiler or cooker, is installed incorrectly or is poorly maintained.

Carbon monoxide can also build up in homes when flues, chimneys or vents are blocked, and can even seep through walls from neighbouring properties. Lit barbeques also emit carbon monoxide, and continue to do so once they’re extinguished. So these should not be used inside or in confined spaces.

There are some simple steps you can take to keep your household safe, these are:

  • Fit an audible carbon monoxide alarm in your home. You can get them from most energy suppliers, DIY stores and supermarkets and many other high street shops. Make sure you buy an audible alarm – it should meet the European standard, EN50291. The alarm will sound if there is too much carbon monoxide is in the air.
  • Have fuel-burning appliances serviced annually by a registered professional.
  • Don’t block ventilation points and get chimneys swept at least once a year.
  • Learn about the danger signs and symptoms of carbon monoxide poisoning.

What are the symptoms?

Carbon monoxide can be fatal and can lead to a range of serious health problems including lasting brain and nervous system damage.

The symptoms of mild poisoning are often similar to common illnesses such as flu or food-poisoning, meaning people often don’t realise they are suffering from carbon monoxide poisoning until the symptoms get worse.

The most common symptoms of mild poisoning are: nausea, dizziness, tiredness, headaches and abdominal pain. Some people may also vomit.

The longer someone breathes in carbon monoxide, the worse the symptoms will get. They may lose their balance, vision and memory. There is also a high chance with high or prolonged exposure that they will fall unconscious or, at worst, die. This can happen within two hours if there is a lot of carbon monoxide in the air.

Other warning signs that suggest carbon monoxide poisoning include other people in your house, flat or workplace experiencing similar symptoms or symptoms disappearing when you leave your home and returning when you come back.

What to do in an emergency

If your alarm goes off or you spot other signs of carbon monoxide:

  • Open doors or windows for ventilation and leave your home immediately
  • Stop using all your cooking and heating appliances that use fuels such as gas, oil wood, charcoal or coal
  • Seek immediate advice from your GP if you think you have carbon monoxide poisoning or, if it is urgent, call 999 for an ambulance
  • Call the relevant emergency advice line: Gas Emergency Service (24 hours) 0800 111 999; Solid fuels (HETAS) 0845 634 5626; Oil (OFTEC) 0845 658 5080
  • Have all appliances serviced and checked. Ensure that you do not use them until you are told it is safe to do so

Where should I position a carbon monoxide alarm?

When placing and using an alarm in the home it is best to follow the instructions that were supplied with the alarm. If you can’t find these then here are a few guidelines that will help you install your alarm in the home:

  • Follow alarm instructions and place alarms in rooms with fuel burning appliances such as boilers in kitchens and fires in the lounge
  • If you want to fix the alarm to a wall then position it at head height ( i.e. your breathing level), however the alarm does not need to be fixed on a wall (e.g. it can be placed on a table, shelf or bookcase)
  • If you have a portable battery alarm you could place this in the room that you spend most of your time such as a lounge or bedroom – you can even move it from room to room with you
  • As with smoke alarms, test your carbon monoxide alarm regularly with the test button (follow manufacturer’s instructions) and replace the batteries annually or when the low battery signal sounds
  • Do not place the alarm in a cupboard, behind furniture, near an outside door or ventilation ( e.g. extractor fans or cooker hoods)
  • Do not place alarms directly next to fires, boilers, cookers or heaters – the alarm should be at least 1 meter away from any of these appliances
  • Do not place an alarm in areas or near sources of high condensation and steam e.g. near kettles, cooker tops, or showers.
  • The alarm should not be placed on a ceiling like a smoke alarm

You should never ignore a carbon monoxide alarm. Check the manufacturer’s instructions to make sure you can recognize the alarm sound emitted when carbon monoxide is present as well as the low battery signal to avoid any confusion. If the alarm sounds, call the relevant fuel advice line for help and seek medical advice urgently if anyone is feeling unwell.

Remember that carbon monoxide alarms must never be used in place of annual safety checks. They are a second line of defence. There is no alternative to proper installation and maintenance of your appliances.

For more technical information and help about alarms and their use contact CoGDEM (the Council for Gas Detection and Environmental Monitoring) on free phone 0800 1694 457.
Don’t take the risk. Make sure you have an audible carbon monoxide alarm in your home and that it works.
For further information and advice on how to stay safe visit

*The study was carried out by Liverpool John Moores University in 2011. Firefighters conducted checks at 22,182 properties across Merseyside. 92 per cent of the properties did not have carbon monoxide alarms.

Website feedback
Was this page useful? Required
Yes, I give permission to store and process my data
We will only contact you regarding this feedback.
Back to top