Carbon monoxide detectors

  • The dangers of carbon monoxide poisoning
  • How to install a carbon monoxide detector
  • How to keep boilers and gas appliances safe from carbon monoxide leaks

It’s estimated that between 30 and 50 people die each year from carbon monoxide (CO) poisoning, and many more are injured from unknowingly inhaling this colourless and odourless gas.

Installing a carbon monoxide detector, and ensuring boilers, ovens and other appliances are properly fitted and maintained will help to keep your home and family safe.

Checking your appliances for carbon monoxide

Carbon monoxide is produced when gas appliances like boilers, built-in ovens or freestanding cookers aren’t fully burning their fuel. This usually happens if they have been incorrectly or badly fitted, not properly maintained, or if vents, chimneys or flues become blocked.

It’s not just gas-burning products that can pose a carbon monoxide risk. Any product burning oil or solid fuel (coal, wood, petrol) can produce carbon monoxide – so heaters, fires and oil-fired boilers can also be affected.

Carbon monoxide is colourless, tasteless and has no smell, making it difficult to recognise – but there are ways to spot a potential risk. Along with fitting a carbon monoxide detector (see below), the Gas Safe Register has identified some tell-tale carbon monoxide signs:

  • yellow or orange cooker flames – gas flames should be crisp and blue
  • soot or yellow-brown staining around or on appliances
  • inconsistent boiler pilot lights which frequently blow out
  • more condensation inside windows than usual.

If you think your boiler or oven is showing signs of carbon monoxide, you should stop using it immediately and contact a professional engineer to examine it. The NHS also has details of potential carbon monoxide poisoning symptoms to look out for.

Gas appliances should be installed by a professional

Gas appliance maintenance

Buying a new gas appliance

Take a look at Which?’s independent lab test review of boilers, built-in ovens and freestanding cookers – each revealing the products we recommend as Best Buys – to ensure you choose the best appliance for your home.


Protecting your home from carbon monoxide poisoning begins the moment you get your new appliance home. It’s important to find a reliable professional with Gas Safe Register accreditation to install any new gas appliance – find recommended engineers in your area on Which? Local, or go to the Gas Safe Register website.

For solid fuel appliances, you should choose a HETAS approved engineer to install your appliance.


Getting a good boiler service every year will help to ensure your boiler is functioning as it should be. Our boiler servicing video guide takes you through what to expect, and our review of boiler services and boiler repairs has the results of our boiler servicing satisfaction survey.

Which? has also examined boiler servicing contracts to see if an annual service contractwith a company like British Gas or Homeserve is worth paying out for.

How to buy a carbon monoxide detector

An audible carbon monoxide alarm is a good way to ensure you’re immediately alerted to any carbon monoxide in your home.

A carbon monoxide alarm is cheap and easy to fit

Carbon monoxide detectors are widely available from DIY stores, usually found in the smoke detector aisle, or through your energy supplier. But just as a smoke alarm doesn’t detect carbon monoxide, your carbon monoxide alarm isn’t a replacement for a standard smoke alarm – you’ll need one of each.

Prices on carbon monoxide alarms from brands like Kidde, FireAngel, Honeywell and Ei Electronics range between £15 and £35.

Your carbon monoxide detector should:

  • have an audible alarm – rather just than a ‘colour change’ or ‘back spot’ indicator tool – which will sound an alarm when it detects CO
  • have a British Standard EN 50291 mark – also written as BSEN 50291 or shown with the CE mark
  • have a British or European Kitemark, Loss Prevention Certification Board (LPCB) or equivalent testing approval mark.

Fitting your carbon monoxide detector

Setting up and installing your carbon monoxide detector is a straightforward DIY task – simply follow your carbon monoxide detector’s instructions. We asked the Council of Gas Detection and Environmental Monitoring (CoGDEM) for some additional guidance:

  • Place the alarm in a central location, like a hallway or landing – not in a cupboard or close to an outside door.
  • Fix the alarm to a wall at head height, or place it on a table or bookshelf.
  • Place the alarm at least a metre away from boilers, fires, cookers or heaters, but ideally in the same room as the appliance – though not directly above a source of heat or steam.
  • Test your alarm regularly using the test button and replace batteries annually or when the low battery signal sounds.

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