Dubbed the "silent killer", carbon monoxide poisoning kills up to 50 people a year in the UK.

If you suspect carbon monoxide poisoning, call the gas emergency line on 0800 111 999

The gas is invisible, and has no taste and smell. Symptoms can be confused with those of flu.

The British Gas campaign is designed to raise public awareness of the fact that the symptoms of carbon monoxide poisoning may not be obvious.

The campaign is being fronted by Dr Mark Porter, from BBC's Watchdog Healthcheck.

Dr Mark Porter is leading the campaign

Dr Porter said people should be aware that at the time of year when flu was most common carbon monoxide poisoning could be a potential cause of symptoms.

Leaflets, which will be sent to GP surgeries and health centres in the new year, feature a picture of headache tablets, with the slogan: "Every year hundreds of people make the mistake of trying to fix a boiler with these."

Flu-like

Dr Porter said: "The symptoms of carbon monoxide poisoning can be similar to the flu which can make diagnosis difficult."

A British Gas spokesman said: "This is the key time of year when people complain of flu-like symptoms - and we want to make sure they are aware of another potential cause of the symptoms."

Symptoms to watch out for:

Increased tiredness Drowsiness Headaches Flu-like symptoms ie nausea Chest pains Stomach pains

Gas appliances such as fires, water heaters and boilers can be affected.

If an appliance is leaking carbon monoxide, it is usually because it has been installed or maintained inadequately.

There can also be problems if the flue is blocked, or there is no ventilation.

Check appliances

Warning signs of a potential problem include sooty stains around the appliance showing carbon has escaped, a yellow or orange flame when it should be blue, and an odd smell when the appliance is on.

Appliances should be checked once a year by a CORGI registered engineer.

Mike Wheeler, a spokesman for the Health and Safety Executive said: "It seems a lot like flu, but if it clears up when you go away for a few days and then it comes back when you return home, that might suggest a source of carbon monoxide in the home."

He warned rooms should have ventilation: "People try and make their homes more draft free and that's not necessarily a good idea."

People can be particularly vulnerable if they leave a leaky gas appliance on while they sleep.

Appliances should never be covered, and flues, airways and ventilation should not be blocked.