Best carbon monoxide detectors

We've reviewed carbon monoxide (CO) detectors from Aico, FireAngel, Firehawk, Google Nest and Kidde, along with a collection of unbranded models, to find the alarms that will detect CO and sound every time you need them to, as well as the worst that simply don't detect the danger. 

We test carbon monoxide detectors to British Standard BS EN 50291-1 and the alarms we select to be Best Buys need to detect carbon monoxide in every one of the 20+ gas detection tests we carry out, whether we're testing them with low but dangerous concentrations of the gas or catastrophically high concentrations.

Read on to find out which carbon monoxide alarms passed all of our tests and are Best Buys.  

The best carbon monoxide detectors from our tests    

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The carbon monoxide detectors we tested  

All the carbon monoxide detectors we tested are listed in alphabetical order below.

Only logged-in Which? members can view the best carbon monoxide detectors from our tests.

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Aico Ei3018

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Most recently tested Dec 2019

Standalone or interlinked Interlinked

Battery type Mains with back-up battery

Need to know Can be used with other AI alarms, 10-year guarantee

FireAngel FA3313

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Most recently tested May 2023

Standalone or interlinked Standalone

Battery type Disposable

Need to know Five-year warranty

FireAngel FA3322

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Most recently tested May 2023

Standalone or interlinked Standalone

Battery type Sealed 10-year battery

Need to know Digital display, five-year warranty

FireAngel FA3820

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Most recently tested May 2023

Standalone or interlinked Standalone

Battery type Sealed 10-year battery

Need to know 10-year alarm and battery life, five-year warranty

Firehawk CO7B-10Y

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Most recently tested May 2023

Standalone or interlinked Standalone

Battery type Sealed 10-year battery

Need to know 10-year warranty, data from the alarm can be downloaded to a phone

Kidde 4MCO

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Most recently tested December 2019

Standalone or interlinked Interlinked

Battery type Mains with back-up battery

Need to know Can be linked to other Kidde and Firex alarms, seven-year warranty

Best smoke and heat alarms: see which alarms were effective and reliable in our tough lab tests

Kidde 2030-DCR

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Most recently tested May 2023

Standalone or interlinked Standalone

Battery type Disposable batteries

Need to know Can be wall-mounted or freestanding, can't be linked to other alarms

Kidde K10LLDCO

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Most recently tested May 2023

Standalone or interlinked Standalone

Battery type 10-year sealed battery

Need to know 10-year alarm life and warranty, can be freestanding or wall-mounted, can't be linked to other alarms

Kidde K5CO

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Most recently tested May 2023

Standalone or interlinked Standalone

Battery type Disposable

Need to know Seven-year warranty, can be freestanding or wall-mounted, uses disposable batteries, can't be linked to other alarms

Kidde K7CO

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Most recently tested May 2023

Standalone or interlinked Standalone

Battery type Disposable

Need to know 10-year alarm lifetime and warranty, freestanding or can be wall-mounted, can't be linked to other alarms

Kidde K7DCO

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Most recently tested May 2023

Standalone or interlinked Standalone

Battery type Disposable batteries

Need to know 10-year battery lifetime and warranty, digital display shows the CO levels in the air, freestanding or wall-mounted, can't be linked to other alarms

Google Nest Protect Smoke + CO Alarm

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Most recently tested May 2023

Standalone or interlinked Interlinked

Battery type Mains powered or disposable battery versions are available

Need to know Smart alarm, 10-year alarm lifetime, comes with CO and smoke detectors, can be linked to other Nest alarms

Which? Don't Buy carbon monoxide detectors

The worst carbon monoxide (CO) detectors don't sense when there's a build-up of CO, they don't sound the alarm and they pose a danger to anyone who has one installed in their home. 

That's why every carbon monoxide detector we assess needs to pass every one of our 20+ gas detection tests. Any carbon monoxide detector that fails to detect a build-up of the deadly gas in our tests is a Don't Buy.

Almost every Don't Buy carbon monoxide detector we've tested was bought from sellers listing cheap and unbranded detectors on online marketplaces. So avoid buying this kind of alarm and look for detectors from brands you recognise sold through well-known high street and online retailers.

As well as failing to detect carbon monoxide, many of the cheap and unbranded Don't Buy detectors we've tested come with instructions telling owners not to install them in the kitchen, which is where you'll find potential sources of CO in many UK homes (gas boilers, hobs and ovens). It's essential to have a carbon monoxide detector in the same room as any fuel-burning appliances in your home.

How we test carbon monoxide detectors

We expose each carbon monoxide (CO) detector to various concentrations of the gas and we measure response times, loudness and we check the instructions, too.

• CO tests start at 30 parts per million (ppm) where alarms shouldn't trigger. At 50ppm alarms should sound between 60 and 90 minutes. At 100ppm the alarms should sound between 10 and 40 minutes. And at 300ppm the alarms take three minutes to sound.  
• We expose the alarms to a catastrophic amount of CO (5,000ppm) to see whether they detect the gas and continue to work afterwards.
• All alarms need to hit a noise level of 85dB at a distance of one metre. 
• We read the instructions to make sure the advice provided will lead to safe installation and operation. 
• Finally, we test the alarms 90 days after their initial tests to see if they're still detecting CO reliably. 
• All carbon monoxide detection tests are carried out to British Standard BS EN 50291-1.

We regularly revisit the carbon monoxide detectors on sale to see if there are any more popular models that need testing, and when we find them we do.

Find out more about how Which? is not influenced by product manufacturers or retailers and how your support helps us to stay editorially independent

Where to place and install a carbon monoxide detector 

Fit your detector high up in the same room as the potential source of carbon monoxide, around 15cm from the ceiling and at least one metre away from boilers, cookers and fires. 

Make sure it’s not directly above a source of heat or steam. It doesn't need to be fixed to a wall – a shelf will be suitable.

What to do when a carbon monoxide detector goes off

• Open all doors and windows The first task is to open all doors and windows to ventilate and try to clear some of the deadly gas.
• Turn off gas appliances and leave the house Switch off all fuel-burning appliances, such as boilers and fires. Regardless of whether you feel ill or well, remain outside until you've spoken to a doctor or called the emergency advice line.
• Don’t switch on the lights, smoke or strike a match Once the alarm has sounded, avoid using light switches, smoking or striking a match (to light a candle, for example) as this could create a spark that could catch fire.
• Seek medical advice If you feel ill or exhibit any of the symptoms of carbon monoxide poisoning (see below) after your alarm goes off, contact your doctor immediately or call 999 for an ambulance.
• Call the emergency advice line If you believe your carbon monoxide emergency was caused by a gas appliance, call the Gas Emergency Service on 0800 111 999. If you use oil to heat your home, call Oftec on 01473 626 298.
• Arrange to have your appliances serviced If your boiler, heater, stove or fire is producing dangerous levels of carbon monoxide, there's something wrong with it, and it will need to be serviced by a professional. Find a recommended, local Which? Trusted Traders heating engineer in your area.  

Can you use rechargeable batteries in a carbon monoxide detector?

If your carbon monoxide detector uses replaceable batteries, avoid using rechargeable batteries in it. Rechargeables drain more quickly than disposables and this means that you will need to replace them more often. 

If you don't want the hassle of changing batteries at all, go for an alarm with a sealed battery designed to last the lifetime of the detector.

See which are the best AA and AAA batteries in our tough lab tests and compare big brands with supermarket own-brands

Why is my carbon monoxide detector beeping?

Beeping or chirping coming from a carbon monoxide detectors can mean one of three things:

• Low battery If your detector uses replaceable batteries, a chirp or beep every minute is your cue to replace the batteries.
• End of life warning All CO detectors have a set lifetime which can be as long as 10 years. Chirping every 30 seconds is the sign that your alarm is ready to be replaced. 
• Malfunction Chirping can also mean that the alarm isn't working properly.

Keep the instructions handy so you can use them to interpret your alarm's beeps and chirps.

Who needs to have a carbon monoxide detector in their home

If you live in a house or flat that’s entirely powered by electricity, you won’t need a carbon monoxide detector. But if you have a fuel burning (gas, LPG, oil, wood) boiler, fire or stove, you should have one in every room where fuel is burned.

Even if you don't have any fuel-burning appliances in your home, carbon monoxide can seep through walls. So, if you live in a semi-detached home or a terrace and your neighbour burns gas, LPG, oil or wood, the safety-first approach would be to install a carbon monoxide detector.

How to select a carbon monoxide detector

Choose a carbon monoxide detector from a well-known brand that's widely available on the high street or online. Retailers such as Argos, B&Q, Currys, John Lewis, Homebase, Screwfix and Wickes only stock carbon monoxide alarms from well-known brands.

Cheap and unbranded alarms that you might find online for under £10 can’t always be relied on to detect carbon monoxide and to sound the alarm. Every unbranded carbon monoxide alarm we've tested has failed to detect the killer gas and every one is a Don't Buy. 

How many carbon monoxide detectors do I need?

You will need a carbon monoxide detector for every room that carbon monoxide could be produced in. This means that if you have gas boiler in the kitchen and a gas fire, open fire or log burner in the living room, a minimum of two detectors would be advisable. 

Gas distribution network Cadent also recommends installing detectors on every floor of your home and outside bedrooms.

How to test a carbon monoxide detector

Test your alarm regularly using the test button, and replace the batteries annually or when the low battery signal sounds. 

Sealed battery alarms have a battery that will last as long as the alarm and so the battery will not need to be replaced.

How to avoid a carbon monoxide build-up

1. Check for tell-tale signs of carbon monoxide A lazy yellow or orange flame on the hob, dark staining on fuel-burning appliances, your boiler's pilot light blowing out and increased condensation are all carbon monoxide warning signs to look out for.
2. Install a reliable carbon monoxide detector Go for a carbon monoxide detector from a well-known brand that you can buy from reputable high street and online retailers. Avoid cheap and unbranded detectors from online marketplaces. 
3. Ensure all gas appliances are professionally installed and maintained Make sure all of your fuel-burning appliances are installed and serviced regularly by a gas installer with a Gas Safe Register accreditation.
4. Keep flues, vents and chimneys clear An obstruction such as a bird’s nest could block a chimney and lead to a build-up of carbon monoxide. So if you have a chimney or flue, have it swept once a year.
5. Replace old carbon monoxide detectors Carbon monoxide detectors have a set lifetime after which time the sensors start to fail and the alarm will need to be replaced. Carbon monoxide detectors emit a chirping sound to warn you that it's almost time for a replacement.

Spot carbon monoxide poisoning symptoms

The most obvious symptom of carbon monoxide poisoning is a headache. Other symptoms can feel similar to a dose of the flu, fatigue, food poisoning, a hangover or a virus. 

But unlike with the flu or food poisoning, you won’t have a temperature. The symptoms will become worse the longer you’re exposed to carbon monoxide.

Carbon monoxide poisoning symptoms to look out for include: 

• Headache
• Breathlessness
• Confusion
• Dizziness
• Nausea
• Stomach ache
• Tiredness
• Collapse and unconsciousness

I live on a boat, do I need a carbon monoxide detector?

Living space on a houseboat can be limited and with keeping water out a vital consideration, ventilation can sometimes be poor. 

With fuel being burned to power the vessel, heat water and to provide heating, it's essential that carbon monoxide detectors are installed where fuel is burned and where you will be sleeping.

Should I take a carbon monoxide detector on holiday?

If you go to a holiday cottage in the UK or a hotel, it will need to be fitted with carbon monoxide detectors. But what you'll find when you travel abroad isn't so clear. 

Carbon monoxide alarms are small, light, easy to pack and you will find affordable options among our Best Buys if you're looking to take one with you.