What noise?
That chirping noise.
I didn’t hear it. Maybe it was the blackberry.
Does it chirp?
Well, sometimes, yeah. I’m not sure what it’s telling me. At least it rings when there’s a phone call.
Wait, there it is again.
OK, I heard it this time. It’s the smoke detector, isn’t it?
I think so.
I check upstairs and downstairs and all around and discover that the house is not burning down. The noise stopped….temporarily.
It started up again at about 2:00 this morning and then chirped periodically all night. Tuffy P went on-line to discover some web entries suggesting that our our brand of hard-wired smoke detectors sucks and can chirp without a fire for all kinds of reasons from dust to old back-up batteries. Of course it isn’t obvious how to get at the back-up batteries or even what they look like.
I should say that I didn’t get much sleep last night. Sleeping through a chirping smoke alarm is most difficult. I’m going to try to not be grumpy today.
27th Street 
expiry date is years away…S the electrician says to check the backup battery first.
If you read the label on the back of the smoke detector closely it may tell you, as mine did, that it expires in 7 years. And, true to the label, 7 years after we installed all of ours, they have been going, one by one. I bought new ones and installed them, but read the label–there’s an expiration date in another 7 years… I think I should buy stockes in Kidde Fire Protection.