Carbon monoxide is a poisonous gas that has no smell or taste. Breathing it in can make you unwell, and it can kill.
Carbon monoxide (CO) is sometimes referred to as the "silent killer". Every year in the UK, over 200 people go to hospital with suspected carbon monoxide poisoning, which leads to around 40 deaths.
A headache is the most common symptom of mild carbon monoxide poisoning. Other symptoms include:
- nausea (feeling sick) and vomiting
- tiredness and confusion
- stomach pain
- shortness of breath and difficulty breathing
Symptoms of carbon monoxide poisoning can be similar to those of food poisoning and the flu. However, unlike flu, carbon monoxide poisoning does not cause a high temperature (fever).
Read more about the signs and symptoms of carbon monoxide poisoning.
Carbon monoxide is difficult to detect because it has no smell, taste or colour. This means you can inhale it without realising.
Carbon monoxide is produced when fuels such as gas, oil, coal or wood do not burn fully. When a fire burns in an enclosed space, such as a room, the oxygen is gradually used up and replaced with carbon dioxide. The fuel is unable to burn fully and releases carbon monoxide.
After breathing in carbon monoxide, it enters your bloodstream and mixes with haemoglobin (the part of red blood cells that carry oxygen around your body), to form carboxyhaemoglobin.
When this happens, the blood is no longer able to carry oxygen, and this lack of oxygen causes the body’s cells and tissue to die.
What causes carbon monoxide to leak?
Incorrectly installed, poorly maintained or poorly ventilated household appliances – such as cookers, heaters and central heating boilers – are the most common sources of carbon monoxide.
Blocked flues and chimneys can also prevent carbon monoxide escaping, allowing it to reach dangerous levels.
The risk of carbon monoxide poisoning can occur at any time, in any home or enclosed space.
Read more about the causes of carbon monoxide poisoning.
Being aware of the signs
It's very important to be aware of the risk of carbon monoxide poisoning and to look out for warning signs.
You should suspect carbon monoxide poisoning if:
- other people in your house, flat or workplace fall ill with similar symptoms
- your symptoms disappear when you go away (for example, on holiday) and return when you come back
- your symptoms tend to be seasonal – for example, you get headaches more often during the winter when the central heating is used more frequently
- your pets also become ill
Other possible clues of a carbon monoxide leak include:
- black, sooty marks on the front covers of gas fires
- sooty marks on the walls around boilers, stoves or fires
- smoke building up in rooms due to a faulty flue
- yellow instead of blue flames coming from gas appliances
What to do if you suspect a leak
If several people in the same building develop flu-like symptoms without a temperature, and you think it could be linked to a carbon monoxide leak, you should:
- immediately stop using all your cooking and heating appliances that use fuel other than electricity
- open all of the windows in your house or building
- move away from the source of the carbon monoxide
- call the Health and Safety Executive (HSE) Gas Safety Advice Line on 0800 300 363 for advice (freephone service)
- visit your GP as soon as possible
If you have a carbon monoxide leak, ask a suitably qualified engineer to inspect your cooking appliances, central heating and water heating appliances, to check they are safe.
Treating carbon monoxide poisoning
You will need oxygen therapy treatment in hospital if you have been exposed to a high level of carbon monoxide, or have symptoms that suggest exposure.
Oxygen therapy involves breathing in 100% oxygen through a tight-fitting mask (normal air contains about 21% oxygen). Breathing in concentrated oxygen enables your body to quickly replace carboxyhaemoglobin.
Read more about how carbon monoxide poisoning is treated.
The time it takes to recover depends on how much carbon monoxide you have been exposed to and how long you have been exposed to it.
Around 10-15% of people who have severe or life-threatening carbon monoxide poisoning develop long-term complications, such as damage to the brain or heart.
Read more about the complications of carbon monoxide poisoning.
Carbon monoxide is a danger to everyone, but certain groups are more vulnerable. These include:
- babies and young children
- pregnant women
- people with chronic heart disease
- people with respiratory problems, such as asthma
Preventing carbon monoxide poisoning
The best way of protecting you and your family is to be aware of the dangers and identify any appliances in your house that could potentially leak carbon monoxide.
You should install a carbon monoxide alarm, as this will detect a leak in your home and give out a high-pitched noise when gas levels are high. They are available from DIY and hardware stores. However, alarms are not a substitute for maintaining and regularly servicing household appliances.
Read more about preventing carbon monoxide poisoning.