The government has launched a publicity campaign aimed at cutting the number of people who fall prey to deadly carbon monoxide gas.

It is thought that up to 50 people in the UK die each year as a result of accidental carbon monoxide poisoning - another 150 end up in hospital.

Because the poison - which can be the byproduct of faulty gas appliances - is odourless, tasteless, and invisible, it is difficult to identify the problem until symptoms have begun.

Anything from a blocked chimney or flue or a badly-maintained boiler can cause dangerous levels of the gas to build up in homes.

And leaving car engines running in unventilated spaces can be equally dangerous.

A recent MORI poll revealed the extent of people's ignorance about carbon monoxide.

One in ten could not name any potential source of carbon monoxide in their home, and one in three did not know that if a gas flame is burning orange instead of its normal blue, it could be pumping out the gas.

Andrew Wall, from Carbon Monoxide Support, said: "Everybody is vulnerable, and the main cause is people's ignorance.

"It can be avoided through proper maintenance of appliances and increased awareness."

To increase people's knowledge on the subject, the Department of Trade and Industry is adding warnings to 20m fuel bills, as well as distributing leaflets through GP surgeries and running TV adverts.

Dr Kim Howells, DTI Consumer Affairs Minister, will be visiting three cities with the worst record on carbon monoxide deaths - Cardiff, Birmingham and Belfast - to launch a regional awareness campaign.

No oxygen

Oxygen, which keeps the body's tissues alive, is carried around the bloodstream by red blood cells.

Carbon monoxide molecules stick to red blood cells and stay there, making far fewer cells available to carry oxygen molecules.

This means that the body is progressively starved of oxygen.

The symptoms of poisoning can be subtle to start with.

Victims may develop headaches, dizziness or fatigue and weakness, and may have a flushed face.

People with heart conditions are far more vulnerable to carbon monoxide poisoning, as are people who smoke or drink alcohol.

If not spotted, permanent damage can occur in parts of the body which require a lot of oxygen, such as the heart and brain.

One treatment used to reverse carbon monoxide poisoning is "hyperbaric oxygen therapy", which combines 100% oxygen with increased pressure.

It can help remove the carbon monoxide molecules stuck to the red blood cells, hastening the poison's exit from the body.

Tips to keep homes safe from the gas include:

• Look out for warning signs - gas flames that burn orange instead of their normal blue, sooty stains above appliances or solid fuel appliances that burn very slowly or go out
• When moving into a new home, find out when the boiler was last serviced - and get it serviced once a year
• Buy a carbon monoxide detector - although these are no substitute for servicing a boiler