I have no idea. That sounds cheaper than trace radioactives to me, but the photoelectric ones are reliably more expensive than ionization, at least around here

I have no idea. That sounds cheaper than trace radioactives to me, but the photoelectric ones are reliably more expensive than ionization, at least around here. And a lot harder to find, too. I'm pretty well annoyed that ionization types are still allowed and the default, if it doesn't show. "YOU LIT THE KITCHEN ON FIRE!" alarms are nice, but radically less useful than "Hey, something's smoking and has been doing so for a while and you're all asleep," based on empirical evidence from the studies on fire deaths. Fires while someone's awake and (often enough) involved in the process are important to warn about, but if one has to pick between that and the stuff that kills people at night, I'd bias towards the ones that (a) meet the requirements they're supposed to meet and (b) provably save lives. I suppose I ask too much... :/