A Beeping Dilemma. A widowed elderly neighbour came over half an hour ago to ask me to sort out her smoke alarm which she said was "beeping." She had the step stool ready for me and a spare battery, so I changed them over and tested it. Worked fine. Then we heard another quiet "beep." "Are you sure it's this one? Have you another?" "Yes, there's one upstairs." So I changed that one. We were talking for a bit on the first floor and then we heard another "beep." I said, "Have you anything else that could beep?" She thought for a bit and then realised she'd got a battery operated carbon monoxide detector, that her son had put on top of a window pelmet in a back room four years ago. So I changed the batteries in that which solved the problem. The batteries in the smoke alarms had been in for the same length of time, so it was worth changing them.