Are your radiators hot? Or merely lethal?

Funny how the first really cold snap always seems to coincide with the complete breakdown of the central heating system. Hester Lacey takes preventive action

The nights are drawing in, the frosts are becoming more frequent, and this is the time of year when even the hardiest among us are thinking of switching the central heating back on. Or, at least, trying to switch the central heating back on. If your system has been idle all summer, it may not cooperate. British Gas deals with an average of 30,000 central heating breakdowns every month; the first cold snap last month more than doubled the number of emergency callouts.

A little regular TLC could save you considerable hassle at this time of year. "After your home and car, your central heating system is your next biggest investment and it needs to be cared for properly. Many of the spate of early winter breakdowns could be prevented," says Anne Morton, spokeswoman for British Gas. Ensuring your boiler and heating system is properly maintained isn't simply a matter of keeping you cosy, either. Faulty gas appliances can let carbon monoxide gas - odourless and potentially lethal - escape into your home.

The Council for Registered Gas Installers (Corgi) has just launched a campaign to raise awareness of the dangers of carbon monoxide. Every year, carbon monoxide poisoning claims around 30 lives in the UK, and causes hundreds more injuries. Corgi advise that appliances should be checked for safety annually by a registered gas installer, ventilation should never be blocked, and DIY projects involving gas should never, ever be on the weekend to-do list (you'd be surprised what people get up to). British Gas also recommends fitting a BS 7860 audible CO detector; they cost £35 and sound a loud alarm if CO is detected.

There are other possible dangers, though, if your system hasn't been properly fitted. "When I moved I was told that the heating system was brand new, so there shouldn't be any problems at all," says one recent home-buyer. "Luckily, I wouldn't dream of switching a central heating system on without having had it checked by British Gas. The thermostat wasn't connected to anything so the boiler was getting hotter and hotter and could have exploded. And half the radiators were connected to the hot water system instead of the central heating, so you couldn't have the hot water on without the heating coming on as well."

It's a legal requirement that anyone who works with gas must be Corgi-registered, whether they work for a large organisation or independently. The Corgi card acts as ID, and the reverse of the card gives details of the different types of gas work the engineer is competent to undertake. All British Gas engineers are, of course, Corgi registered.

Steve Newiss, 44, is their Engineer of the Year; he has worked for British Gas for 28 years, since he was 16 years old. It's a hi-tech business now, he says. "We all have laptops and we log in in the morning to get our day's work. We have all the info on 8,000 appliances available on disc and we can order any parts we need through the terminal for next-day delivery, as well as doing all the billing and banking. It's made a fantastic difference."

This is a busy time of year for Steve, who works in the area around Keighley, Leeds. "At this time of year it's mainly faults, where in summer it's mainly servicing; every job on my terminal today bar one is a fault. The first few weeks of the winter turn-on period there's a real surge in jobs." He reckons that 70 to 80 per cent of breakdowns can be fixed on the first visit; the rest need a part that's not in his van, or need the system to be left on test and re-checked.

Most of Steve's callouts are routine, but he has seen some alarming set-ups. "The most dangerous are where people have fitted their own appliances," he says. "People do dangerous things to save a bit of money. I've seen people fit gas fires without a chimney; they've knocked a hole in the wall and sent the flue into the cavity wall. Or they've connected gas pipes with a bit of hosepipe." One man had fitted a gas wall-heater to a door, so he could swing it open and heat his patio as well. Not a good idea.

In extreme situations, says Steve, he will disconnect the gas supply. "If there is a situation classed as immediately dangerous, where there's a risk to life or property, we disconnect, though that doesn't happen often."

To make sure your heating system is ready to face the winter, his tip is to run it regularly through the summer. "Don't wait till the frosty weather," he says. "Run the system periodically for 10 minutes over the summer; if there's a wet day, put it on for half an hour to dry the washing on the radiators." Keeping the system in limber means it will be ready for the cold weather, and if it's not, at least you'll know well in advance and you'll avoid the first-frost rush.

What else can you do? British Gas offers a full maintenance and emergency response central heating care contract, which gives immediate, 24-hour cover and priority access to their national network of 7,000 engineers, from £15 a month. Optional extras include adding electrics, plumbing and appliances to the cover offered. Anne Morton also recommends checking your own radiators when you do switch on. If they are hot at the bottom and cold at the top they will need to be bled to remove trapped air. If the radiator is hot at the top and cold at the bottom the problem could be either the radiator or the central heating system. If only one radiator has this problem check the radiator valves are fully open.

When radiator valves have been off all summer, occasionally they can stick - try turning the valve up and down a few times to release it. Keeping insulation up to scratch round boiler and pipes and in the loft will keep you warmer, avoid burst pipes and keep your bills down. Or you could invest in large quantities of thermal underwear, and prepare to shiver.

British Gas: 0845 609 0664, www.house.co.uk

Corgi: 0870 401 2300, www.corgi-group.com