Carbon monoxide (CO) gas is produced by burning fuel. Even in low doses, CO gas is poisonous and can cause loss of consciousness and death. Around 30 people in the UK die every year from carbon monoxide poisoning.Carbon monoxide has no smell and is colourless. This makes it easy to breathe in without realising it.

Domestic appliances fuelled by natural gas, oil, kerosene (paraffin), coal, wood and liquefied petroleum gas (LPG) – for example, propane, may produce CO gas. Burning charcoal, running cars, and smoking cigarettes also produce CO gas.

Common household appliances should produce very little CO when they are well maintained and safely used. Damaged appliances, or those that are not serviced regularly, may produce higher levels of the gas than normal and become dangerous.

Burning fuel in an enclosed or unventilated space, for example a car engine running inside a garage or a faulty heating boiler in a kitchen, presents the biggest danger for CO poisoning.

CO poisoning may also be caused by inhaling fumes from cleaning fluids and paint removers that contain methylene chloride. The methylene chloride is converted into carbon monoxide when we breathe it in.

When we breathe in carbon monoxide it gets into our blood stream, and mixes with haemoglobin (carboxyhaemoglobin). Haemoglobin is the part of red blood cells that carry oxygen around the body. When carbon monoxide mixes with haemoglobin it is unable to carry oxygen. This lack of oxygen causes the body tissue and cells to die.

Treatment

People with carbon monoxide poisoning will be given 100% oxygen through a closely fitting mask (normal air is only 21% oxygen).

Some patients will also receive Hyperbaric Oxygen Therapy (HBO) within 6 hours of exposure to CO. HBO is a treatment that saturates the body with pure oxygen, helping it to heal. 

HBO is given to people who have had their oxygen supply cut off or reduced, pregnant women, people in a coma or with a history of loss of consciousness, as well as people who have shown abnormal ECG readings or reduction in brain activity.