A joint report by the Health and Safety Executive and British Gas says children under the age of 10 are the group most at risk.

Carbon monoxide poisoning has killed 11 youngsters during the past five years while another 202 needed treatment.

Warning signs of dangerous appliances include a strange smell, stains, soot or discolouring around a gas fire, water heater or boiler and an appliance burning with a yellow or orange flame when it should be blue.

Gas appliances require an adequate supply of fresh air and an unobstructed chimney or flue to operate safely

Barry Watkinson HSE

Figures from engineering consultancy Advantica show 110 people have died while another 953 needed treatment.

During the same period 31 people aged 60 and above died while another 81 needed treatment.

Incidences of carbon monoxide poisoning peak during winter, and especially in the run-up to Christmas, the report says.

And younger children are less likely to show clear symptoms, recurring headaches, stomach pains, nausea and fatigue, which can be misdiagnosed as a heavy cold or flu.

HSE head of gas and transport safety division Barry Watkinson said: "Gas appliances require an adequate supply of fresh air and an unobstructed chimney or flue to operate safely."

Under normal circumstances gas is a safe and reliable fuel

Chris Bielby British Gas

British Gas is advising that all gas appliances be installed and regularly maintained by a qualified Council for Registered Gas Installers (Corgi) engineer.

Central heating appliances caused 78% of the 403 incidents investigated.

But 21% of them had been regularly serviced by a Corgi engineer.

And British Gas says additional peace of mind can be provided by the installation of a British Standards approved carbon monoxide detector.

Chris Bielby, head of quality and standards, said: "Under normal circumstances gas is a safe and reliable fuel, so to see so many children die unnecessarily as a result of poorly maintained gas appliances is tragic."