Why is my smoke detector chirping?

A smoke detector usually chirps because its battery is running low. A single short chirp about once a minute is the most common sign that it wants a new battery.

There are a few other common reasons. Most smoke detectors should be replaced 10 years after the date they were made, which is printed on the back, and many models chirp when they reach that age. Some units have a sealed 10-year battery that can't be swapped, so a chirp means the whole detector needs replacing. A battery that is loose, a battery door that isn't fully closed, or the wrong battery type can also set it off. Hardwired detectors have a backup battery that runs down too.

Here is what to do. Put in a fresh battery of the type listed on the unit, then hold the test button until it sounds. If it keeps chirping, check the date on the back. Some models need a reset after a battery change, and the instructions on the unit will explain how. Don't pull the battery and leave it out. That quiet detector is the one that should wake you during a fire.

Fire safety agencies suggest testing every detector once a month. Fortress tests smoke and CO detectors on its spring visits and puts in fresh batteries each fall. If a hardwired unit needs new wiring, a licensed electrician should do that work.