I got one of them smoke detectors, and I didn't think it worked. Most of the time it just irritated me. I guess it didn't like my cooking because it seemed to always get noisy when I was cooking. Once it got noisy when i was sawing a hole in the bathroom wall to install a medicine cabinet too. Never once did it smoke. It seemd like almost every year it started chirping and would not stop till I changed the battery. That was really annoying when I was trying to sleep.
Last week it started chirping again, and kept me awake all night. I did not have another battery to make it happy either, and at 3am all the stores were closed. Since it would not let me sleep, I finally got out of bed, and decided to modify it so it no longer needed batteries. I cut the cord off an old toaster and soldered the wires to the battery clips. Then I plugged it into the closest outlet. In less than a second it started smoking, then it caught on fire. I had to toss a bucket of water on it to make out the fire.
Well, now I know it works. It smoked and started on fire, so I know that it does what it's supposed to do, since the instructions said it's for both smoke and fire. Better yet, it no longer chirps, so I wont have to buy batteries for it anymore. Best of all, it's stays quiet when I cook now. That makes me happy. I'm quite pleased with it, now that I know it works properly and no longer annoys me.