Carbon Monoxide Safety

Advice on safety checks, symptoms and prevention

What is carbon monoxide?

Every year there are around 25 deaths from accidental carbon monoxide poisoning in England and Wales.

Carbon monoxide (CO) is a colourless, odourless, tasteless, poisonous gas produced by incomplete burning of carbon-based fuels, including gas, oil, wood and coal.

Carbon-based fuels are safe, but when the fuel does not burn properly excess CO is produced, which is poisonous. Breathing it in can make you unwell, and can kill at high exposure levels.

When CO enters the body, it prevents the blood from bringing oxygen to cells, tissues, and organs. Levels that do not kill can cause serious harm to health if breathed in over a long period. In extreme cases paralysis and brain damage can be caused as a result of prolonged exposure to CO. Increasing public understanding of the risks of CO poisoning and taking sensible precautions could dramatically reduce this risk.

Signs to look out for at home

There are signs that you can look out for which indicate incomplete combustion is occurring and may result in the production of carbon monoxide:

  • Yellow or orange rather than blue flames (except fuel effect fires or flueless appliances which display this colour flame).
  • Soot or yellow/brown staining around or on appliances.
  • Pilot lights that frequently blow out.
  • Increased condensation inside windows.

Symptoms of carbon monoxide poisoning

Early symptoms of CO poisoning can mimic many common ailments and may easily be confused with food poisoning, viral infections, flu or simple tiredness. Symptoms to look out for include:

Headaches or dizziness



Loss of consciousness


Chest or stomach pain

Erratic behaviour

Visual problems

If you, your family or anyone you come into contact with experiences any of the above symptoms and believe they may have been exposed to carbon monoxide, they should seek urgent medical advice from either their GP or an A&E department.

The symptoms of exposure to low levels of carbon monoxide can be similar to those of food poisoning and flu. But unlike flu, carbon monoxide poisoning doesn't cause a high temperature (fever).

The symptoms can gradually get worse with prolonged exposure to carbon monoxide, leading to a delay in diagnosis.

Your symptoms may be less severe when you're away from the source of the carbon monoxide.

If this is the case you should investigate the possibility of a carbon monoxide leak, and ask a suitably qualified professional to check any appliances you think may be faulty and leaking gas.

Long-term exposure to low levels of carbon monoxide can also lead to neurological symptoms, such as difficulty thinking or concentrating and frequent emotional changes – for example, becoming easily irritated, depressed or making impulsive or irrational decisions.

Severe Symptoms

Breathing in high levels of carbon monoxide gas can cause more severe symptoms, including:

  • Loss of consciousness – in cases where there are very high levels of carbon monoxide, death may occur within minutes.
  • Intoxication - impaired mental state and personality changes.
  • Vertigo – the feeling that you or the environment around you is spinning.
  • Ataxia - loss of co-ordination caused by damage to the brain and nervous system.
  • Breathlessness and tachycardia (a heart rate of more than 100 beats per minute).
  • Seizures – uncontrollable electrical activity in the brain causing muscle spasms.
  • Chest pain caused by angina or a heart attack.

At Risk Groups

Carbon monoxide is a danger to everyone, but certain groups are more vulnerable than others:

  • Babies and young children
  • Pregnant women
  • People with chronic heart disease
  • People with respiratory problems

Pets are often the first to show signs of carbon monoxide poisoning. The smaller an animal or a person is, the faster they'll be affected. Investigate the possibility of a carbon monoxide leak if your pet becomes ill or dies unexpectedly and it is unrelated to age or existing health condition.

What causes carbon monoxide to leak?

Carbon monoxide is produced when fuels such as gas, oil, coal and wood don't burn fully.

Burning charcoal, running cars and the smoke from cigarettes also produce carbon monoxide gas.

Gas, oil, coal and wood are sources of fuel used in many household appliances. Incorrectly installed, poorly maintained or poorly ventilated household appliances such as cookers, heaters and central heating boilers are the most common causes of accidental exposure to carbon monoxide. The risk of exposure to carbon monoxide from portable devices may also be higher in caravans, boats and mobile homes.


Gas fires

Central heating systems

Water heaters


Open fires

Other possible causes of poisoning

  • Blocked flues and chimneys – this can stop carbon monoxide escaping, allowing it to reach dangerous levels.
  • Faulty or blocked car exhausts – a leak or blockage in the exhaust pipe, such as after heavy snowfall, could lead to a build-up of carbon monoxide.
  • Paint fumes – some cleaning fluids and paint removers contain methylene chloride (dichloromethane), which can cause carbon monoxide poisoning if breathed in.
  • Burning fuel in an enclosed or unventilated space – for example, running a car engine, petrol-powered generator or barbecue inside a garage, or a faulty boiler in an enclosed kitchen.
  • Smoking shisha pipes indoors – shisha pipes burn charcoal and tobacco, which can lead to a build-up of carbon monoxide in enclosed or unventilated rooms.

Preventing carbon monoxide poisoning

Maintaining and servicing appliances

Boilers, cookers, heating systems and appliances should be installed and regularly serviced by a reputable, registered engineer. Don't attempt to install or service appliances yourself. Anyone carrying out work on installations and appliances in your home must be registered with a relevant association, such as the:

Carbon monoxide alarms

Install a carbon monoxide alarm in your home to alert you if there's a carbon monoxide leak. However, an alarm isn't a substitute for maintaining and regularly servicing household appliances.

You can buy a carbon monoxide alarm from a DIY or hardware store. Make sure it's approved to the latest British or European Standard (BS Kitemark or EN50291).

Maintaining chimneys and flues

Make sure all chimneys and flues are swept regularly by a qualified sweep who's a member of the:

Engine exhaust fumes

To help protect you from carbon monoxide poisoning caused by vehicle exhaust fumes:

  • Don't leave petrol-fuelled lawnmowers or cars running in the garage
  • Make sure your car's exhaust is checked every year for leaks
  • Make sure your exhaust isn't blocked before turning the engine on

Other safety tips at home and in the workplace:

  • Make sure rooms are well-ventilated and don't block air vents. If your home is double-glazed or draught-proofed, make sure there's still enough air circulating for any heaters that are in the room.
  • Avoid oversized pots on your gas stove, or place foil around the burners.
  • Don't burn charcoal in an enclosed space, such as on an indoor barbecue.
  • Fit an extractor fan in your kitchen (if it doesn't already have one).
  • Don't use gas-powered equipment and tools inside your home if you can avoid it. Only use them in a well-ventilated area, and put the engine unit and exhaust outside.
  • Wear a safety mask when using chemicals that contain methylene chloride.
  • Don't sleep in a room that has a gas fire or paraffin heater without a working flue.
  • Never use ovens or gas ranges to heat your home.

What to do if you suspect a carbon monoxide leak

  • Stop using all appliances, switch them off, and open doors and windows to ventilate the property.
  • Evacuate the property immediately – stay calm and avoid raising your heart rate.
  • Call the gas emergency number on 0800 111 999 to report the incident, or the Health and Safety Executive (HSE) Gas Safety Advice Line on 0800 300 363.
  • Don't go back into the property – wait for advice from the emergency services.
  • Seek immediate medical help – you may not realise you've been affected by the carbon monoxide, and going outside into fresh air won't treat any exposure by itself.

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