I was a firefighter for seven years, many years ago.

One winter evening, we were dispatched to a chimney fire. After we extinguished it (with the homeowner's hose and a chimney nozzle) I did a walk through of the house and attic to check for extension.

I found his smoke detectors hanging open, with the batteries removed. When I asked the homeowner if he wanted some new batteries for them (we kept free batteries on the engine), he happily took them. When I asked him how long his smoke detectors had been without batteries, he quickly answered: "Since Christmas morning."

I have no doubt as to where the new batteries went...