[dogsgobork]

I hadn't really thought about it, but that makes a ton of sense. Smoke detectors typically use an alpha-emitter, smoke absorbs alpha particles, so a failure to detect is what triggers the alarm. The cost for a false-negative is much higher than a false-positive, so that's what the detector should default to.

[dghughes]

I have a Nest smoke alarm and it was bad for going off due to the vapours from showers, boiling water when cooking.

But to the credit of Nest/Google/Alphabet they replaced it free of charge. It was just an off-the-cuff comment I made on Twitter and Nest said send it back. They sent a new one, a new model, and when it arrived I sent back the older model. The new model is much better essentially zero false positives due to water vapour.