Michael O'Gorman has been stalking a silent killer. Two hundred people die each year, and the culprit is everywhere: invisible, odour- less and tasteless.

A mysterious spate of deaths in bathrooms first caught his attention, back in 1968. But Cast aside the Psycho image of Norman Bates and a stabbing knife - the killer here - carbon monoxide - is far deadlier.

The gas is produced when fossil fuels don't burn properly. Those bland appliances, familiar domestic tools, can kill: gas and oil boilers, fireplaces, wood stoves, barbecues, gas and solid fuel cookers, space heaters and cars. Water heaters gave the game away, alerting Michael, a heating engineer from Fritwell near Bicester. "People were blocking up their bathroom vents, since wet bodies and cold air don't mix. But the gas water heater needed a fresh supply of oxygen, otherwise it makes carbon monoxide."

Horrified, he began tracking down tales of poisoning. "Whenever I came across a story in the paper, I would get in touch with the people involved," he says. Soon Michael's nation-wide network went official, forming the Gas Safety Action Group.

"I burnt the midnight oil for years, bashing away at an old typewriter with two fingers, trying to shame politicians," he explains. Three years ago, the Government relented and ran an awareness campaign. It was a victory, but not enough. Fifty per cent of British people still don't realise that gas fires cause CO poisoning, according to a recent survey. This ignorance could leave 25,000 people feeling under the weather. Low doses of carbon monoxide produce flu-like symptoms: headaches, fatigue, nausea, dizzy spells and confusion.

Dubbed 'the Great Imitator', the sickness often leads GPs astray. This proved fatal for 26-year-old Karen Weise. In 1996, she and her fiancee, Michael Wood, 30, died from CO poisoning. The boiler flue suffered a down-draught, forcing toxic fumes into their bedroom. Karen, a nurse, had been to the hospital the day before her death because she was suffering from nausea and palpitations. Had the doctors recognised her symptoms, the couple could have been saved.

Listen to your body, the experts advise. That's how a girl saved her family of five from lethal carbon monoxide fumes, just weeks after the deaths. The six-year-old started screaming with a headache in the early hours of the New Year.

"Kerri was our heroine," says Yvonne Wiltshire, who breathed fumes from the newly-installed gas fire in their Banbury home. "If she had not woken us up, we could have all been dead." The family was treated with oxygen, which often must be "forced" into the bloodstream. The treatment is similar to that given divers suffering the bends, and severe cases often are rushed to special facilities in Portsmouth.

"Blood is suicidal,"Michael explains. "Platelets, given a choice, absorb carbon monoxide instead of oxygen." This can lead to collapse, coma, brain damage - and for 200 people each year - death.

The risk is widespread, as 80 per cent of UK homes use gas. "North Sea gas is so pure that it can not be smelled," he warns. Danger signs include stains, soot or discolouring around a gas fire or water heater. "One of the problems is that anybody can set up a fireplace shop. I've got an advert here, selling £15,000 franchises, 'no experience necessary'. You can't just open a chemist's shop, because that's dealing with poison.

"But CO is one of the biggest poisons next to nerve gas and there's no controls on it."

Contact The Gas Safety Action Group at 24 The Lane, Fritwell, Bicester, Oxfordshire OX6 9QW. An international group also provides CO support; ring local contact Pam Mercier on 01865 863049.

Story date: Thursday 09 December

Converted for the new archive on 30 June 2000. Some images and formatting may have been lost in the conversion.