No, the place isn't on fire.
By the time I had my pants on and had grabbed my shoes, phone, and laptop (all handy at my bedside - I was not wasting time in a fire alarm to hunt things down, just grabbing the important things in front of me), the alarm had stopped. I went through the house checking anyway, but nothing.
I can only assume the construction dust got to one of them, even though they're all covered in plastic to prevent that. (It's certainly getting to me, in spite of heavy application of antihistamines. My doctor thinks that's the reason my eye was unable to focus the other day. My dust allergy has been working overtime the past week, unsurprisingly.)
The thing that gets me is that it happened at 5:40 in the morning. I expect the dust is rather the opposite of stirred up right now. Which makes me worry that I'm in for more of the same. I heard a single alarm bleep! the other day, but it was just one, so mostly left me going where'd that come from? (Was it us? the neighbors? Not the alarm at all, but one of the construction workers' tools?) Having now heard a dozen or so more bleeps out of it, I'm sure it was the same. So am now going to try to go back to sleep while wondering when it will go off next.