Carbon monoxide detectors

  • Carbon monoxide poisoning - hidden dangers and how to spot symptoms
  • How to install a carbon monoxide detector or alarm to keep your home and family safe
  • Carbon monoxide leaks - keeping boilers and gas appliances safe to use
Man installing a carbon monoxide detector

Installing a carbon monoxide detector could save you from a colourless, odourless killer

Carbon monoxide poisoning kills an estimated 30-50 people each year in the UK, and many more are injured or become seriously ill from unknowingly inhaling this colourless and odourless gas.

Installing a carbon monoxide detector, and ensuring it is in the right place, will alert you to the presence of carbon monoxide, helping to keep your home and family safe.

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 (or a combined alarm). 

We've rigorously tested smoke alarms to keep your home and family safe. The best alarms scored top marks in four British Standard fire tests, the worst failed to go off in the times required by the British Standard. 

Which? members can click to find a Best Buy smoke alarm. Not yet a member? You get access to all of our online reviews, including our smoke alarm test results, with a £1 trial to Which?

Carbon monoxide checks on your appliances

Carbon monoxide is produced when gas appliances, such as 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 and serviced, or if vents, chimneys or flues become blocked.

Gas flame inside the gas boiler

Gas appliances should be installed by a professional

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

Carbon monoxide is colourless, tasteless and odourless, 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 that 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 early symptoms of carbon monoxide poisoning are similar to early flu, including tiredness, nausea, an upset stomach and flu-like symptoms. The NHS Choices website has further details of potential carbon monoxide poisoning symptoms to look out for. If you feel unwell and suspect carbon monoxide poisoning, go to your doctor, call NHS 111 (where available) or, if it's urgent, phone 999 for an ambulance. Tell them you feel your symptoms may be related to carbon monoxide poisoning.

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.

Carbon monoxide detectors are widely available from DIY stores, usually found in the smoke alarm aisle, from supermarkets, 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 for carbon monoxide alarms from brands including 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.
Carbon monoxide detector

A carbon monoxide alarm is cheap and easy to fit

Fitting your carbon monoxide detector

Setting up and installing your carbon monoxide detector is a straightforward DIY task - simply follow the detector's instructions. You should also:

  • Install a carbon monoxide detector in every room containing a fuel-burning appliance.
  • Always read and follow the manufacturer’s instructions on siting, testing, servicing and replacing the alarm. Pay particular attention to the unit’s battery life and when it will need replacing.
  • Position the alarm at head height (your breathing level), but it doesn't need to be fixed to a wall (a shelf is often suitable). The alarm should be at least 15cm from the ceiling.
  • 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.

You can save money on batteries - our tests have revealed that the best batteries that will power your devices for hours longer than the worst. Click to find out more about the best batteries.

Protection from carbon monoxide: gas appliance maintenance

Protecting your home and family from carbon monoxide poisoning is a three-stage journey that includes buying, installing and regularly servicing your gas appliance.

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.

We survey thousands of Which? members about problems they've had with their home appliances, to find out which brands are the most reliable. 

Installation

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 (formerly CORGI) to install any new gas appliance, as they can legally and safely undertake gas safety work.

Find recommended engineers in your area on Which? Local - Which? Local brings together thousands of recommendations from Which? members across the UK - or go to the Gas Safe Register website.

If you’ve recently had home improvement work done that involved gas, and you’re not sure if a registered engineer did the work, you can nominate your property for a free safety check. 

Your gas supplier may be able to provide you with a free gas safety check if you meet certain criteria, such as being of pensionable age or chronically sick or disabled. 

For solid fuel and Biomass appliances, choose a HETAS approved engineer to install your appliance.

Servicing

Getting a good boiler or gas appliance service every year will help to ensure they are functioning as they should be. You can find out what to expect by taking a look at our boiler servicing video guide.

A HETAS-registered installer can service and clean solid fuel and Biomass appliances, and a HETAS-approved chimney sweep can help keep your chimney clear.

Gas suppliers have a duty to provide free annual gas safety checks to some older, disabled or chronically sick people – or those who live with them, or with a child under five. Call the company you get your gas bill from.

If you rent your home, you should expect your landlord to have your gas appliances safety-checked each year and serviced regularly.

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