Carbon monoxide detectors

Carbon monoxide detectors

Carbon monoxide detectors

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Carbon monoxide detectors

Our guide will help you to install a carbon monoxide detector and keep your gas appliances safe to use.

Carbon monoxide detector


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.

You can help keep your family and home safe by installing a carbon monoxide alarm, and ensuring it's in the right place. This will alert you to the presence of carbon monoxide.

Do bear in mind that your carbon monoxide detector doesn't detect smoke, just as a standard smoke alarm doesn't detect carbon monoxide, so 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, while the worst failed to go off in the times required by the British Standard. 

Don't miss our Best Buy smoke alarm recommendations. 

Carbon monoxide checks on your appliances

Carbon monoxide is produced when cooking or heating 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.

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, wood burning stoves, barbecues 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 alarm (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 headache, dizziness, 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 will immediately alert you to any carbon monoxide in your home. So make sure you pick an alarm with an audible alert, rather than a detector with just a coloured indicator. 

Carbon monoxide alarms are widely available from DIY stores, usually found in the home safety aisle. You can also get them from supermarkets, or through your energy supplier or heating engineer. 

Prices for carbon monoxide alarms from brands including Kidde, FireAngel, FireBlitz, Honeywell and Ei Electronics range between £15 and £35.

Your carbon monoxide alarm should:

  • Have an audible alarm that sounds an immediate alert when it detects CO - rather just than a 'colour change' or 'black spot' indicator tool
  • Be labelled to show it meets EN 50291 - also written as BS EN 50291 - and also shown with the CE mark
  • Have a British Standards Kitemark, or Loss Prevention Certification Board (LPCB) mark or equivalent European testing approval mark.

Fitting your carbon monoxide detector

Setting up and installing your carbon monoxide alarm is a straightforward DIY task - simply follow the manufacturer's instructions.

You should:

  • Install a carbon monoxide detector in every room that has 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) or above. 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. 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.

It's also good advice to buy an alarm with a sealed-for-life battery. These are tamper proof - so you can't take the battery out - and should last the life of the alarm.

Our lab tests have revealed that the best batteries will power your devices for hours longer than the worst. Find out more about the .

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, oil or solid-fuel appliance.

Buying a new gas appliance

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

Take a look at our 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.

Pilot light on a gas appliance


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 a local, recommended engineer in your area on Which? Trusted Traders - each trader has been assessed and checked by Which? professionals. 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.

For oil-fired appliances, choose an Oftec approved engineer to install your appliance.


Getting your boiler or gas appliance serviced every year will help to ensure it's functioning as it should be. You can download our free checklist and find out more about getting the best boiler service.

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. An Oftec-registered installer can service and clean your oil-fired appliances.

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. This is a legal requirement, so do ask your landlord for an up-to-date copy of the gas safety certificate.

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