Fire?!?

Our fire alarm went off three times in the night last night. Needless to say, I didn't sleep too well.

I've learned not to be too startled by the fire alarm because we have one just outside the kitchen that goes off all the time when I'm cooking, but this one was downstairs, and in the middle of the night when no one was up. Each time it just beeped a few times and then stopped. The first time we weren't even sure that was what it was, but we went downstairs and looked around, sniffed for smoke, felt of the walls, etc. Nothing. Then we'd go back to bed and get settled down, only to have it happen again. After the third time I laid awake for an hour or more plotting an action plan if the house WAS on fire. Thankfully, we never had to carry it out.

I'm not sure what was causing this. It is a battery-operated fire alarm, and they always "chirp" when the battery is low, so I don't think that was the problem. If anyone has any suggestions, I'd love to hear them.