I have found that the 2 am nuisance alarms are typically just beeeping saying the battery is dead. The batteries as the building cools down drop below the low battery threshold (though not exactly the same, a lead calcuim battery will drop 3.75 mV per degree C). Then the building warms back up and the beeping stops. As I am cheap and won't replace the batteries until death, my wife or kids are a lot better at finding these than myself. But this may not address the issue you brought up.
Phantom alarms always seem to happen at night, and those typically for me have been the neighborhood spider crawling in and sometimes setting up home in photoelectric types. The offending unit usually blinks red while alarming if memory serves. That is the only way I know of short of opening them all up.
Sad thing is, my wife is the only one who gets up for these problems. I barely come to, and my kids never miss a moment of sleep.
Shane
