Carbon monoxide: very bad. Bad in a death way.

Warning! says the big red sticker on my gas fire. "This appliance has been disconnected." There's a little box below and inside somebody has scrawled the words "spilling fumes". I don't like that. It sounds bad.

So my boiler had been on the blink for a while. It's controlled by a little clock with four nodules in it - two red, two blue - which are rotated around a dial to set times at which the heating will turn on and off. Red for on, blue for off. This process was working perfectly until one of the red nodules, doubtless sick of being adjusted one time too many, made a dramatic bid for freedom by detaching itself from the unit and leaping onto the floor of the airing cupboard.

Once retrieved, this tiny lump of plastic could not be re-attached. The resulting imbalance caused my poor boiler to become hopelessly confused. The red "heating on" nodule would flick into action at 6am, followed at 9am by the blue "heating off" nodule. And then, just when it expected another red, it got blue instead.

"But I'm already off," it must have exclaimed to itself in whatever language boilers speak. I wish I could say how it decided what course of action to take, but all I know is that from that point onwards, my boiler stopped listening to me and started doing its own thing. It became a teenager, essentially.

I didn't grow up with gas. The tiny Yorkshire village in which I lived for the first part of my life, had no gas supply. My earliest memory of gas is of someone coming home in a TV drama, switching the light on and blowing up the house. So I've always been wary.

Thus I put up with the idiosyncracies of my boiler for a long time. It still made hot water, still generally warmed the house, still kicked into life at 2am whirring and screeching like a train full of mechanical ostriches. All was well, for the most part, and when it wasn't I'd go downstairs, stick the gas fire on full and open the inside doors. I know this was very, very bad for my carbon footprint. I didn't find out until later just how bad it was for my carbon monoxide footprint.

But there are few things quite as disheartening as a cold home. So when winter really started to get its teeth in, I finally bit the bullet and called up somebody to come and check my boiler. British Gas were helpful, informing me that, had I only joined their monthly protection plan before the fault developed, I would now be reaping the rewards. However, since I was joining with a broken boiler, I would have to pay £27 a month instead of the £12 offered to those with squeaky clean heating.

"Faulty timer eh?" said the man in the call centre, after I'd explained to him for the ninth time that I had a faulty timer. "Well... just bringing up some examples here, you could be looking at £240 for that alone, so it really makes sense to join the plan." He sounded as trustworthy as a door-to-door kidney salesman. I called someone local, and my inexperience with gas put me instantly out of my depth.

"What's the problem?" he asked.

"I think it's the timer," I replied.

"Why?" he said.

"It's hard to explain. A bit fell off and it's been weird ever since, " I said.

"I'd best have a look," he said.

"Can you check my fire as well?" I asked.

"Ok. What's wrong with that?" he said.

"I don't know. Might be something wrong with it. I can't tell," I said.

"Alright," he said.

"Do you check the cooker too?" I asked.

"Erm... not normally," he replied.

"No, no, of course," I said. "That would be silly."

"I suppose I could have a look if you want," he said.

"I'm sure it's fine," I said.

The boiler, it turned out, was also fine. He fixed that with a new timer, costing £30 (although I'm sure the £240 ones are awfully nice). But then he inspected the gas fire. And then he inspected it more closely. Then he peeked up the chimney and then, I like to think, he flailed, grabbed a shelf to steady himself from the shock, before disconnecting the thing entirely. And out came the red sticker.

"Spilling fumes," it emerges, is pretty bad. Fire, explosions, poisoning - it's lucky, claimed the boiler man, that there wasn't an accident. He says the chimney's blocked so badly it probably can't be used any more. Who am I to dispute it? My only other source of wisdom is the British Gas call centre, and that didn't go well the first time. Although I'll keep the number. After all that carbon monoxide, I might well be needing new kidneys.