Mother-of-three Sue Jaffer thought she was suffering from a particularly bad run of colds and winter aches and pains when carbon monoxide leaking from her boiler began to poison her last year.

Suffering classic symptoms of carbon monoxide poisoning - flu-like aches, tiredness, swollen glands and nausea - she became so ill that she could no longer work.

She said: "I got the flu in October and I just didn't get better. I got a sinus infection, an ear infection, and went 50% deaf.

"I stopped working altogether and started work in my study, which was precisely where I was being poisoned."

The source of Sue's ills was eventually traced to the family's boiler. Once it was fixed, she began to feel better almost immediately.

Her case illustrates that it isn't just people living in low-rent accommodation who are susceptible to what the tabloids call the "Silent Killer".

Chartered physiotherapist Paul Leary fears that many people could be suffering the effects of CO poisoning without even realising it.

Heating units in his Huddersfield surgery were condemned six years ago after the gas board appeared to change the way they inspected appliances.

He told BBC News Online that for about five years, the practice's two physios and three part-time receptionists had resigned themselves to winters of sore eyes, sore throats, aches, pains and extreme fatigue.

He said: "We work very hard, so we were not surprised that we felt tired. But the fatigue was so profound that all you wanted to do was shut your eyes and sleep.

"It does worry me sometimes that I might have actually just nodded off - I could have died.

"We are all educated and informed people with a medical background, yet we didn't know what was happening to us."

He said it was only when inspectors noticed that the flues from two open-fronted gas fires in the surgery's consultation rooms were blocked that the problem was arrested. The practice took the decision to replace the fires altogether.

He said: "They removed half a ton of soot from the flues and we all immediately started to feel more full of life, less tired, and generally more well.

"There was no smell, no indication that it was anything other than general winter illnesses that were making us all sluggish and unwell.

"It takes some time for your body to get over the effects. One of the interesting things I have noticed is that over the past five years, I hadn't been able to drink above half a pint without getting terrible headaches the next day.

"I stopped drinking altogether. Obviously my liver just couldn't handle both the fumes and alcohol. But since we have had the flues cleared, I have been able to drink again."

He said that he fears pensioners in particular are vulnerable to the effects of carbon monoxide poisoning, and says that although he welcomes the Department of Trade and Industry's initiative to reduce its effects, the government is still not doing enough.

"It makes me very worried," he said. "Old people in particular tend to block up all the places where drafts come in, but they're also blocking out any ventilation.

"I personally don't think the government is doing enough to prevent illness and deaths from gas fires. I think ultimately open fronted gas fires should be banned, and that CO detectors should be mandatory.

"I feel we got off very lightly here. We could have died, it's as simple as that, and the tragedy is that many people do lose their lives in this way every year."