Best carbon monoxide detectors 2024: Which? Best Buys and expert buying advice

A good quality carbon monoxide detector will sniff out the danger and let you know when there’s carbon monoxide in the air. But there are plenty of ineffective alarms on sale – in fact, a fifth of all of the models we’ve tested were so unreliable and dangerous that we’ve labelled them Don’t Buys.

As it’s important to buy a carbon monoxide detector that won’t let you down, it’s worth doing a little research before heading to the shops. Our video (below) shows how to buy the best carbon monoxide detector, how much you should spend, what to look for in the shops and the types of carbon monoxide detector to avoid.

Who needs a carbon monoxide alarm?

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 (gas, LPG, oil, wood) burning boiler, fire or stove, you should have one in every room where fuel is burned.

How much do carbon monoxide detectors cost?

It pays to spend a little more when buying a safety product like a carbon monoxide detector. Our carbon monoxide detector tests show that you’re more likely to end up with a safe and reliable carbon monoxide detector if you pay around £20. Simpler models can cost as little as £17, while for an alarm with a screen and a long-life sealed battery, you'll typically pay £25 or more.

But pay £10 or less and you run the risk of buying an alarm that won’t be reliable and wouldn’t pass our rigorous carbon monoxide tests.

We've found that the carbon monoxide detectors that failed our tests all cost around £10 or less - as do many other identical lookalike brands.

Types of carbon monoxide detector

Sealed battery carbon monoxide detectors 

As the name suggests, the battery for this kind of detector is sealed inside the unit; once the battery runs out, the alarm will chirp, prompting you to replace the unit. The battery unit is tamper proof and some have lifetimes of around 10 years before they will need to be replaced. Buying this kind of carbon monoxide detector is a good idea if you want to avoid needing to replace the batteries every couple of years or so.

Replaceable battery carbon monoxide detectors 

You’ll need to replace the batteries every two to three years if you have this type of detector, though the alarm will still have a finite lifetime of between five and 10 years. You can find out the best value and longest lasting batteries using our battery reviews.

Detectors with replaceable batteries are usually a few pounds cheaper than sealed battery detectors, but you will need to buy replacement batteries after a few years, and this brings the prices to about level.

Smart carbon monoxide detectors 

When this kind of carbon monoxide alarm detects dangerous levels of carbon monoxide, it sends a message to your smart phone as well as sounding the alarm. If you live a connected life through your phone, this kind of neat tech may up your street. But there is a premium to pay if you want to smart detector.

The Nest Protect Smoke + CO Alarm, for example, is £89 – that’s around four times as much as a conventional detector, but it is two products in one.

Early versions will last for seven years before needing to be replaced. The second generation will last for 10 years.

Read our review of the Nest Protect Smoke + CO Alarm. 

Patch carbon monoxide detectors 

The cheapest way to detect carbon monoxide in your house would be to buy a patch carbon monoxide detector, but read on before you do. Rather than sound the alarm, this kind of detector changes colour when there’s carbon monoxide in the atmosphere. A pack of two costs around £5.

We think the safest option for everyone would be to choose a detector that sounds the alarm rather than just indicating there’s a problem. If there was a dangerous carbon monoxide build-up in the middle of the night, a patch changing colour won’t wake you up to let you know. So whatever kind of carbon monoxide alarm you buy, go for one that sounds the alarm.

The best carbon monoxide detectors that we've tested and rated are 85db or louder in our tests – that’s about as loud as a food mixer.

What brands are the most effective?

Choose a carbon monoxide detector from a brand that is widely available from shops such as Argos, B&Q, Currys, John Lewis, Homebase, Screwfix and Wickes - established big firms like these only stock alarms from well-known companies.

Cheap alarms that you might find online for under £10 can’t always be relied on to detect carbon monoxide and to sound the alarm. We found this to be true of all of the alarms that failed our tests and are highlights as Don't Buy carbon monoxide alarms.