Learned something very interesting last night...
Around 12:30 I wake up to the smoke alarm upstairs going off. Quick do a house check. Nothing out of place, downstairs alarms aren't going off.
I reset it and went back to bed.
Around 2:30, same thing. This time I do a full house sweep checking for anything that might be out of the ordinary. Still nothing.
As I'm heading back upstairs, it goes off again, but this time I notice that the upstairs hall smells a lot like bleach, which I had used on the grout in my bathroom right off the hall where the smoke detector is.
So, I hopped onto the internet and found out that the new photovoltaic smoke detectors can be set off by strong smells, including bathroom products.
So, I hosed the shower down to get rid of the bleach, turn on the fan in my office window to do an air change, and waited.
No more alarms.
Not something you want to wake up to in the middle of the night, that's for sure.