I just replaced two battery operated detectors that started randomly blasting. I bet they were dusty. Too bad this thread didn't pop up a month ago.
Well, they were pretty old anyway. Probably better technology in the new ones.
All the hard wired smoke detectors in my house have battery backup and will beep when the batteries get low, always at 3 am on the coldest night of the year. Since I have vaulted ceilings in my house some of these detectors require a tall step ladder to get to. I ended up removing the batteries from the hard to get to detectors but still have enough coverage from the detectors with batteries to make me feel safe if there ever is a power outage.
We've had them go off due to a spider; and vacuum them biannually. More recent models monitor for smoke as well as other combustion byproducts but seem to be more sensitive to steam from things like hot showers.
Perhaps the antics of yours was caused by a power interruption?
Smoke detectors use a radioactive isotope that sends a constant stream of decay products across a gap to a sensor. When something gets into the gap and interferes with the stream (smoke, steam, dust, bugs, dew) then the sensor calls it a fire.
In our house, false alarms are caused by all of the above. The dew was particularly annoying because the detector was right next to the ducting of a solar exhaust fan which was open to the outside air. Dew points occur very very early in the morning around here.
We discovered the "steam" issue by having a detector too close to the bathroom while we were using the shower. Again, a very inconvenient time to have the smoke detector go off, no matter what you're doing in there.
A sixth source of false alarms is the isotope itself. After 10 years it's decayed away to the point where there's not enough happening for the sensor to reliably sense it. If you have a 10-year-old detector then it's time to just throw it away and get a new one. I'm not aware of any way to buy a new source, although entrepreneurs have tried.
David Hahn - Wikipedia, the free encyclopedia
The hard-wiring is part of the residential building code and may even be national by now. At first the concern was that batteries weren't good enough, so at least one detector should be hard-wired. (Our rental home actually had a fire caused by faulty hard-wiring to the smoke detector. The detector didn't detect it because the smoke never reached the detector.) Now the concern is that homes are big enough for residents to not hear the detector from one end to the other. The "solution" is to hard-wire all the detectors to the house's power, which can also serve as the communications relay network to alarm them all in the event that one of them goes off.
Golly, it's that time of year again. Guess I'd better go buy eight 9v batteries and get motivated...