OK, once is bad, twice is downright spooky. Tonight about 9pm while watching the movie Chain Reaction, the smoke alarm went off. It lasted about 15 to 20 seconds and then quit. When it's done that before it was due to a candle nearby, but such was not the case tonight. Candles have gotten to the point where they upset my wife's sinuses, so we've stopped using them.
I checked all around, but no smoke. No smell of smoke, no reason for a smoke alarm. We joked that the hydrogen explosions on the movie set it off.
Then around midnight, it went off again. Again for 15 to 20 seconds. Again no smell of smoke, no apparent reason. I checked the attic. I checked outside. No smoke.
I took the battery out and will go get fresh batteries in the morning. But usually when the batteries are dieing, you get a nice occasional chirp and it doesn't stop after 15 to 20 seconds.
* Update - After the 4th time, I made a 1am run to CVS for new batteries. New batteries didn't help, I ended up unplugging the stupid things. I've never had so much trouble. Now I can't sleep.
* Update 2 - this morning I gently took the smoke detectors apart and vacuumed them. Each had a small cobweb in them. Cleaned them good, put them back up and all quiet so far (about 3 hours of experience). I'm afraid to test them though.