Are you certain it's just a smoke detector, or is it one of those smoke and carbon monoxide dectectors?

Similar four am smoke detector experience--high humidity had something to do with it...

" steam or high humidity can lead to condensation on the circuit board and sensor, causing the alarm to sound."

I'll third the high humidity thing - I worked in a restaurant where the fire alarm kept going off. The engineer, at some obscene time of the morning, said that moisture inside the alarm had shorted something.

Why don't you try lighting a fire under the alarm to dry it out?

gah! the exact same thing happened to me couple of weeks ago. 3am beep beep beep. 3:05am another 3beeps and so on. carmina pretends to be sleeping till 4am wishing deep down it will STFU on its own. Can't go on. Unfortunately I have very high ceilings and no ladder in the apt so my first attempt at fixing things was to start poking at the device with the stick of a broom. At 4am. While cussing. Obviously I am not a handyman. Not at 4am. Despite my sincere efforts to make it stop with my elaborate technique, I failed so I had to stack up a chair on a little table and unscrew the stupidity off the wall. At 4am!!! Even I did not know I knew all these cussing words. Oh dear.

It was the battery in the carbon monoxide detector (ahh, I had to search which damn thing was beeping since there are all sorts of beeping things mounted on the ceiling). I hate it when things break in the house. I_hate_it. If something big breaks, I want to move out.

Phew. There. I vented. Thank you and good luck. I have no advice to offer. You wouldn't want it anyway.
Bye now.

Huh. I did not know about the humidity thing. That explains why the one in the dining room is always freaking out.

Glad it was a false alarm, mgl.

Here's something (somewhat unrelated, but maybe anecdotally helpful) I learned the hard way after moving into an old house in Boston: Carbon monoxide detectors aren't as tetchy as smoke detectors, and they don't go off for no reason. Therefore, if you come home from work one night and hear the CO detector blaring, you probably shouldn't unplug it in a fit of annoyance. Because it probably means that the inside of the chimney has collapsed and is blocking the egress of the furnace gas, and the gas has probably made it from the basement to the first floor. And also, you'll wake up wicked sick in the morning, and the furnace repair guy will give you one hell of a lecture about how you could have killed yourself. Oh, and you won't see the cats for 3 days, because they'll be hiding in the attic.

Yo, that's scary, mudpuppie. Colorless, odorless gases freak me out.

Yeah, that is scary, eeesh. I think this one is just a smoke detector though. I was trying to read the fine print on the back at 3:30 this morning and I don't think it said anything about carbon monoxide. If humidity can do it I suppose I have to give up on smoke detectors though - it was miserable last night and it isn't even July yet.

Is there some logical kind of course of action one should follow when the smoke detector goes off, some checklist or something?
Yes, but it's technical, so listen closely:

1. Take a broom or other implement that will reach the ceiling where the detector is mounted and is quite sturdy
2. Beat the detector vigorously with the stick until it falls from the ceiling to the floor
3. Beat it some more
4. Jump on it a few times to sooth your shattered nerves (if you have bare feet, skip this step)
5. Take the offending device to the kitchen
6. Fill the sink with water - right to the top
7. Drop the fucking thing in the sink
8. Go back to bed, turning off your alarm
9. Take the next day off work*

Problem solved.

*If the night this happens on is a Friday or Saturday, take the next available work day off