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Carbon monoxide poisoning

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Carbon monoxide is a poisonous gas that has no smell. Even small amounts can deprive the body of oxygen and even lead to brain damage in severe cases. Here are the symptoms of carbon monoxide you need to know about and how to protect yourself in the first place.

Most of us have either got a smoke detector in our homes or at least are aware that we should have one. But two thirds of UK households don't have a carbon monoxide detector, putting themselves at risk of carbon monoxide poisoning.

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What is carbon monoxide poisoning?

Carbon monoxide competes with oxygen to be carried around the body in our red blood cells. The trouble is, it's hundreds of times more efficient than oxygen at attaching to the cells. That means that even small amounts can deprive our bodies of vital oxygen. In severe cases, it can cause irreversible brain damage by starving the brain of oxygen.

What causes carbon monoxide poisoning?

Carbon monoxide is produced when fuels (gas, coal, charcoal, wood, oil) don't combust fully. That means that poorly fitted or unserviced cookers, boilers and gas fires are the main sources. In summer, barbecues used in enclosed spaces (even if they seem to have gone out) are a major hazard.

The risk of carbon monoxide poisoning is lower than it was in the 'bad old days' when gas was mostly produced from coal. In those days, thousands died in the annual London smogs produced by wood and coal-burning fires in the inner cities. Gas used to be produced from coal, with large amounts of carbon monoxide given off as a by-product.

These days, most of our gas comes from North Sea gas. And now, blocked gas flues or vents, poorly serviced gas fires or ovens, and any solid fuel stove are among the current culprits in carbon monoxide poisoning.

Car exhausts give off carbon monoxide if the engine is left running in a confined space such as a garage. And almost every year brings headlines about unwary campers poisoned by a paraffin camping stove or disposable barbecue left burning in an unventilated tent overnight.

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How common is carbon monoxide poisoning?

There are around 50 deaths from accidental carbon monoxide poisoning in England and Wales every year. And as many as 4,000 medical visits, according to figures from theDepartment of Health - see Further Reading at the end of this leaflet.

However, even coroners may have difficulty diagnosing carbon monoxide poisoning as a cause of death - which means the figures could be a significant underestimate. For hospital visits, the figures may also be skewed because carbon monoxide isn't always recognised as the cause of symptoms. For instance, a study in the USA put the figures at 50,000 people affected per year. If a similar proportion of the UK population was affected, it would bring the figure up to 10,000 medical visits a year.

Who is at risk of carbon monoxide poisoning?

Anyone can be affected by carbon monoxide poisoning. However, you are at higher risk if you:

  • Do not have your gas kitchen and heating appliances serviced regularly.

  • Have a gas appliance fitted by anyone who is not a Gas Safe registered engineer.

  • Have recently had ventilation changes made to your home (eg, installation of double glazing).

  • Use a fire in your hearth and do not have your chimney swept regularly (at least once a year, or twice a year if you are burning wood or coal).

  • Have recently had a cooking or heating appliance installed.

  • Do not have a carbon monoxide alarm.

  • Have noticed an increase in condensation or sooty marks around any of your appliances.

  • Use your gas stove or oven to heat a room as well as to cook, or have brought a barbecue inside a tent for heat.

It is important to remember that even if you have your appliances serviced regularly, your neighbours may not. Living in any accommodation that is not a detached house means there is a risk of carbon monoxide from neighbouring properties.

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Symptoms of carbon monoxide poisoning

Milder symptoms of carbon monoxide poisoning include:

  • Headache.

  • Feeling sick (nausea) or being sick.

  • Dizziness.

  • Flushing.

  • Feeling weak.

  • Abdominal pain.

  • Difficulty in concentrating.

These are all too often mistaken for flu or tummy bugs, with occasionally fatal consequences. If you have vague symptoms, it is more likely that carbon monoxide poisoning is the cause if:

  • Other people in the house have the same symptoms; or

  • Your symptoms are worse at home and better when you're outside.

If you're exposed to low levels of carbon monoxide over long periods, you can develop any of these symptoms along with:

  • Memory problems.

  • Flu-like symptoms.

  • Tiredness.

  • Loss of vision.

  • Problems with sleep, smell or balance.

  • Anxiety.

More severe cases of carbon monoxide poisoning can lead to:

  • Palpitations.

  • Breathlessness.

  • Personality change.

  • Confusion.

  • Heart attack.

  • Convulsions and loss of consciousness.

Carbon monoxide poisoning can often suddenly cause serious symptoms weeks after you've apparently recovered from an acute poisoning episode. Confusion, personality changes and symptoms similar to those of Parkinson's disease can all occur.

Diagnosing and treating carbon monoxide poisoning

If you think you've been exposed to low levels of carbon monoxide, seek advice from your GP. But if there's a possibility you've been exposed to high levels of the poisonous gas, go straight to your nearest hospital's accident and emergency (A&E) department.

Doctors will perform a blood test which will confirm the amount of carboxyhaemoglobin - a chemical formed when carbon monoxide binds to red blood cells. A reading of over 30% indicates a severe case. If you're a smoker, you will already have a higher level of this chemical in your blood, which can make it more difficult to interpret the results.

If your poisoning is mild, it won't usually require hospital treatment, but it's still important to seek advice from a doctor.

Standard oxygen therapy

Standard oxygen therapy may be given if you've been exposed to a high level of carbon monoxide or have severe symptoms of poisoning. In this type of treatment, 100% oxygen is given through a tight-fitting mask. It will allow your body to replace the carboxyhaemoglobin with normal haemoglobin.

How to protect yourself

What we really need is for everyone to take simple steps to stop carbon monoxide poisoning happening in the first place. While it may be tempting to save money by cutting corners, this increases the risk of potentially deadly poisoning.

The problem with carbon monoxide is that it has no smell, no taste and no colour. What's more, symptoms of mild poisoning - poor concentration, feeling sick, general weakness - are very nonspecific. All sorts of medical issues, including viral infections and dehydration, can give rise to the same clinical picture.

But the messages for prevention are clear:

  • Always fit a carbon monoxide monitor in your home.

  • Make sure your carbon monoxide monitor shows a British Standards Kitemark or Loss Prevention Certification Board logo.

  • Have gas fires fitted by a qualified, registered engineer. The same goes for boilers and cookers.

  • Get flues and chimneys checked and cleared regularly.

  • Service your boiler and cooker regularly.

  • Never use barbecues in garages or tents.

Further reading and references

Article history

The information on this page is written and peer reviewed by qualified clinicians.

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