But, you've made me see something I had not spotted before in that you _don't_ see what is unsafe for free on our "don't buy" pages[1]. I have raised this right now with the team!
[1] https://www.which.co.uk/reviews/carbon-monoxide-detectors/ar...
[1] https://www.which.co.uk/reviews/carbon-monoxide-detectors/ar...
"Compared with Best Buy carbon monoxide detectors, the Don't Buy alarms that we've named and shamed on this page just can’t be relied upon to detect the gas and sound the alarm. In our tests, the Don’t Buys failed to detect carbon monoxide in more than one-in-three of our tests. This adds up to 26 failures out of 72 tests. By contrast, the Best Buys passed all 312 of our carbon monoxide gas tests.
The potentially deadly CO alarms all claim to have passed the relevant EU safety standard, EN 50291. But repeated failures in our lab tests – which mirror those of the safety standard – lead us to doubt that they actually did. And we’re as concerned about several lookalike models as we are about the three models that failed our tests.
To find out which models are Don't Buys, as well as our Best Buy carbon monoxide detectors, sign up for a £1 trial to Which?"