Does anyone know anything about fire alarms?

Ours keeps beeping. The maintenance guy was SUPPOSED to fix it today but it looks like all he did was put it back on. Because I just got home from work and it IS STILL BEEPING. I woke up this morning because I was having a really weird dream about playing some game and the beeping sound meant I was winning...and I won alot! Then I realized that the beeping was real. Not to mention, REAL annoying. Tim and I figured it was the battery but when we took it down we didn't see a battery anywhere. So, now we are back at square one since the maintenance guy can't even fix a stupid fire alarm. I seriously feel like we are in a hospital and in the next room there is someone whose heart beat is being monitored (it sounds like one of those obnoxious machines although in hospital scenarios, the beeping is ACCEPTABLE). Arg. If only I was smarter about household stuff.