The problem is that the chirping didn't start until after the power went out this evening. It's kind of hard to climb up on a stepstool n the dark to change batteries. When the power came back on, I took the smoke alarm down, opened the battery compartment (not trivial to figure out how to) and discovered it uses a 9-volt battery.
Which I don't have on hand and I have been home sick for the past day and a half and I really don't feel like going out to the store to buy a bloody battery right now.
Shouldn't the low battery chirp start as soon as the battery is low so one has a reasonable chance?