1. The chirp means low battery
Most smoke alarms chirp about once every 30 to 60 seconds when the battery is low. It is designed to be heard, so it often starts at night.
2. Replace the battery at once
Fit a new one of the type the alarm takes. Check the label or manual first, because alarms take 9-volt, AA, CR123A or sealed lithium batteries.
3. Sealed alarms can’t be changed
Some alarms have a sealed battery that is built to last for the life of the alarm. When one of these chirps, the whole alarm usually needs replacing.
4. Check the date on the back
Smoke alarms don’t last forever. The date of manufacture is printed on the back, and many manufacturers say to replace the whole alarm after about ten years. Check your manual for its figure.
5. Test it every month
Press the test button monthly to check the alarm and its battery. Clean dust from the vents with a vacuum or a soft brush.
6. If the chirping won’t stop
Take the battery out, wait a minute, put it back in the right way round and press the test button. If it still chirps with a fresh battery, the alarm may be faulty, so replace it.