Which? Don’t Buy carbon monoxide detectors

An unreliable carbon monoxide detector (CO alarm) that fails to detect the killer gas and sound the alarm could lead to unthinkable consequences in your home.

The worst carbon monoxide detectors don't sense when there's a build-up of carbon monoxide, posing a danger to anyone who has one installed in their home.

That's why every carbon monoxide detector we test needs to pass every one of our carbon monoxide 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.

Join Which? now to see the carbon monoxide detectors (CO alarms) that are Don't Buys.

The best vs the worst carbon monoxide detectors (CO alarms)

Our tough independent lab tests help us find the best carbon monoxide detectors on the market – the ones you can rely on to sound the alarm when there’s a build-up of carbon monoxide. But the same tests also uncover the carbon monoxide detectors that do a pitiful job and could even endanger your life. 

Many of the carbon monoxide detectors we've tested failed to go off in at least one of our carbon monoxide detection tests. If you have one in your home, the consequences of your alarm not detecting carbon monoxide don't bear thinking about.  

• We test each brand of carbon monoxide detector (CO alarms) more than 30 times in the presence of varying levels of carbon monoxide. We record how quickly they detect the killer gas, how loud they are when they sound and whether they continue to work three months after they were installed. 
• We also expose the carbon monoxide detectors to a catastrophic concentration of carbon monoxide, then check they continue to detect lower levels of the gas afterwards. A good carbon monoxide detector should still be reliable after such an event; a bad one might not be able to recover.
• Inspection of the installation instructions is also important. The worst carbon monoxide detectors have potentially unsafe instructions that advise against installing the detector in the kitchen, which could have deadly consequences if that’s where your gas boiler, or another potential source of carbon monoxide, is.

The best carbon monoxide detectors detect the presence of the gas and sound the alarm every time – and they continue to detect carbon monoxide reliably afterwards.

Avoid the worst carbon monoxide detectors (CO alarms)

Protect yourself and everybody in your home by avoiding dangerously unreliable carbon monoxide detectors.

All of these carbon monoxide detectors have failed to detect carbon monoxide in at least one of our tests and that's why they are Don't Buys that should be avoided. The unbranded alarms were all bought from online marketplaces.

Unbranded Carbon Monoxide Alarm 1 

Unbranded Carbon Monoxide Alarm 2 

Unbranded Carbon Monoxide Alarm 3

Unbranded Carbon Monoxide Alarm 4

Unbranded Carbon Monoxide Alarm 5

Unbranded Carbon Monoxide Alarm 6 

Unbranded Carbon Monoxide Alarm 7

Unbranded Carbon Monoxide Alarm 8

Unbranded Carbon Monoxide Alarm 9

Unbranded Carbon Monoxide Alarm 10

Unbranded Carbon Monoxide Alarm 11

Unbranded Carbon Monoxide Alarm 12

Aico Ei208 Carbon Monoxide Alarm

Find out more about which carbon monoxide detectors (CO alarms) are Best Buys by joining Which? today.