My grandmother's co detector used to go off every time a car drove by her house. She was able to set the sensitivity on it so it stopped doing that.
My dh had co poisoning before (not from our house) so I highly recommend you get a working one in your house asap. You don't want to go through what my dh did.
My smoke detector just started going off when the bathroom door opened right after a shower. It's been up there for years, so I'm thinking it's wearing out. Probably time to buy a new one.
What I'd really like to get are those heat detectors that wind up. No more batteries
