When you move into or buy a new home, no one hands you a guide to how the smoke detectors work. They "chirp," which really means shriek loudly, and you occasionally have to put new batteries in them.

Your smoke alarm’s chirp can be oddly reassuring, a small sound that suggests everything is still working. Yet the device making that noise may already be too old to reliably sense a real fire. The ...

The first time most people hear the quiet chirp of a smoke detector in the dead of winter, it feels like a minor nuisance. It ...