sounds a bit like my house, there is one of those horrible plug in air fresheners in just about every room, i'm continually switching them off....i hate the stuff.
A few summers back my friend and I were visiting a couple that had a herp/snake collection to rival my local zoo. I babysat their giant albino boa (I don't remember what she was exactly) in the bathtub while she was soaking. They had one of those auto plug ins that had to have been set to go off like every seven minutes or so. the first time I heard it I FREAKED OUT. I was terrified that there was some other snake loose in the room and was imagining all sorts of horrible nightmare scenarios. They owned several large/venemous/aggressive reptiles and I didn't know what it was or where it was.
On topic though, I haven't had anything like that happen with an aquarium before, but I did come home from work one day to find my snakes terrarium partway open, with an unwound wire hanger sticking out of it. My snake was nowhere to be seen. I started freaking out.
It turned out he had just decided to hide underneath his water dish (it took me about an hour to coax him out). I confronted my sister (she was my roommate at the time) because well, it HAD to have been her. She ended up telling me that a guy that she had a crush on had brought his two year old over to visit, and they thought it would be cool to show her. She had tried to take it out, but ended up getting scared that it might bite her so she used the hanger to pick him up partway so the little girl could see it.
I nearly killed her.