[djmcmath]

My theory is that (a) I'm gone during most of the waking daylight hours, then when I'm home I'm (b) making too much noise to hear them. The only time that I'm actually quiet enough to hear a smoke detector make a single chirp is when I'm lying in bed.

The alternate theory is that our $15 smoke detectors are actually very sophisticated sleep detectors, such that they can tell when the most responsible person in the house is most asleep, at which point they chirp exactly loud enough to wake that person up without being loud enough to identify which unit is beeping.

[green]Very sophisticated stuff, smoke detectors.[/green]