FYI, fire alarms are designed to become more sensitive as they age/die so if yours is picking up false positives, it’s a good indicator you need to replace it. That, or it really is poor ventilation.

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.

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.

Mine only chirps when the battery dies. Of course, it's always at 3am and I don't have any 9v batteries. Worse now is none of the stores are open 24 hours so you have to suffer 'til 6am or pay $5 at a gas station for a battery.

This would be a good opportunity to get rechargeable batteries and/or an alarm that takes AAs.