Best Carbon Monoxide Alarms UK (2026)

Expert Reviews sprayed a specific aerosol test spray for up to three seconds into a sealed transparent bag containing each alarm. Their rule is that an alarm which doesn't respond promptly isn't recommended, so every alarm here passed. The Netatmo set off within seconds, and the Kidde Lifesaver 5CO was only a couple of seconds behind the more sensitive Kidde 7DCOC.

Not fully. Expert Reviews points out that the test button doesn't actually test the sensor, it only checks that the circuit is working. That's why an alarm's end-of-life and battery warnings matter, and why it's worth replacing an alarm on schedule.

All five here claim a 10-year life, but Expert Reviews notes that CO sensors typically last between five and seven years and only a few manufacturers claim ten. Its advice is to play it safe and replace an alarm a year or two before its life is supposed to run out, and it cites US tests showing alarms over eight years old can fail to detect CO at levels above 400ppm.

Check before you buy. Expert Reviews says both Kidde models, the 7DCOC and the Lifesaver 5CO, won't comply with the new Scottish regulations because they run on batteries that need replacing. The X-Sense, FireAngel and Netatmo alarms have built-in or sealed batteries instead. We haven't checked them against the Scottish rules ourselves, so confirm the current requirements for your home.

Expert Reviews' original top pick, Google's Nest Protect smart smoke and CO alarm, has been discontinued. Tom's Guide reported on 28 March 2025 that Google was ending sales, selling remaining stock until supplies run out and supporting existing units until they expire. Google's announced replacement, a First Alert alarm, was announced for the US and Canada. Because these alarms have a fixed life from the day they're made, a unit from old stock has less life left, so we've left it out. For a smart alarm, see the Netatmo above.

A smart alarm like the Netatmo sends notifications to your phone even when you're not home, useful for a holiday home or checking on a relative remotely. The FireAngel interconnects with other FireAngel alarms so they all sound together. A basic alarm like the Kidde Lifesaver 5CO is much cheaper and just as capable of sounding a loud local alarm, which is all that's needed if someone is always home to hear it.

A combined alarm like the X-Sense SC-08 saves fitting two devices and gives you one thing to maintain. Expert Reviews suggests mounting a CO alarm in the kitchen or next to a fireplace or boiler, and most manufacturers suggest siting it near a gas appliance. See our smoke alarms guide if you'd rather buy dedicated smoke detectors separately.