Carbon monoxide poisoning Dr Rob Hicks Carbon monoxide is known as a silent killer because you can't hear, see or smell it - but you can prevent poisoning and learn how to recognise the early warning signs.

In this article

What causes it? What are the symptoms?

How is it prevented? What's the treatment?

Carbon monoxide is a product of incomplete combustion of natural or petroleum gas. Inhaling the gas reduces the blood's ability to carry oxygen, leaving the body's organs and cells starved of oxygen.

Common sources of carbon monoxide in the home include faulty central heating systems, gas appliances and fires. Blocked flues and chimneys mean the gas can't escape and is inhaled by the unsuspecting individual.

In the UK, about 50 people die each year in their homes from accidental carbon monoxide poisoning.

Car exhausts are also a common source of carbon monoxide. A lethal level of carbon monoxide in the blood can develop within ten minutes inside a closed garage.

The symptoms of mild carbon monoxide poisoning may be non-specific and similar to those of viral cold and flu infections or food poisoning: headache, nausea, abdominal pain, dizziness, sore throat and dry cough.

But, unlike flu infection, carbon monoxide poisoning doesn't cause a high temperature.

In children, the symptoms are similar to those of a stomach upset, with nausea and vomiting.

More severe poisoning can result in a fast and irregular heart rate, hyperventilation, confusion, drowsiness and difficulty breathing. Seizures and loss of consciousness may also occur.

Some symptoms can occur a few days or even months after exposure to carbon monoxide. These may include confusion, loss of memory and problems with coordination.

Carbon monoxide poisoning is preventable, so it's important to be aware of possible causes and how to minimise the risk of exposure by putting these safety tips into practice:

• Have chimneys and flues checked regularly
• Make sure gas appliances and heating systems are inspected every year
• Fit carbon monoxide alarms - available from DIY stores
• Never run cars, motorbikes or lawnmowers in a closed garage

You can also prevent serious consequences by learning to spot the warning signs. Carbon monoxide poisoning may be a possibility if:

• Other people in the home or workplace suffer similar symptoms
• Symptoms tend to disappear when you go away (for example, on holiday)
• Symptoms tend to be seasonal (for example, headaches during the winter when indoor heating is used more often)

Carbon monoxide poisoning can be confirmed by finding high levels in the blood.

Treatment includes making sure the patient is away from any source of the gas, providing basic life support as appropriate and giving oxygen before transferring the patient to hospital.

People who suffer mild poisoning invariably make a full recovery. Between ten and 50 per cent of those with severe poisoning may suffer long-term problems.

This article was last medically reviewed by Dr Rob Hicks in November 2007