Haha, that sounds whack. As far as I know, most fire alarms in Finland (yes, I live here, but I don't mind ordering from other continents because I work in largest fin logistics company!), they seem to send some sort of radioactive particles from point a to point b, and if anything comes to block a particle (say, hazard smoke with all kinds of dangerous things to inhale), it will set off the alarm.
As long as it's not radioactive, I don't mind really using them either. I mean, it's not like my whole idea makes that much sense either. I just hope that when I turn a my first program on it, it won't explode. And if it does, at least it could explode reasonably well to make me forget how much time and money I wasted down the drain!