How often should I change my smoke detector batteries?
Standard battery guidelines
For smoke detectors that use replaceable 9-volt or AA batteries, the National Fire Protection Association (NFPA) recommends testing them monthly and replacing the batteries at least once a year. A common memory aid is to change them when you change your clocks in spring and fall. If the detector chirps, that's a low-battery warning—replace the battery immediately.
Even if the detector seems fine, don't skip the annual change. Batteries can lose power gradually, and a chirping detector may be ignored. Some manufacturers recommend specific brands or types, so check your detector's manual.
- Test monthly by pressing the test button
- Replace batteries at least yearly
- Replace immediately if it chirps
- Follow manufacturer's recommendations
Sealed and hardwired detectors
Many newer smoke detectors come with a sealed 10-year lithium battery. These are designed to last the life of the unit and don't require annual battery changes. However, you should still test them monthly. After 10 years, replace the entire detector, as the sensor itself degrades.
Hardwired detectors with battery backup also need battery replacement—usually annually—even though they run on house power. The battery keeps them working during a power outage.
Replacing the whole detector
Smoke detectors themselves should be replaced every 10 years, according to the NFPA. Even if they still beep when tested, the sensors can become less sensitive over time. Check the manufacture date on the back of the unit. If it's older than 10 years, replace it.
If you have a combination smoke and carbon monoxide detector, follow the same schedule. CO sensors also degrade and may need replacement sooner—check the manual.
- Replace entire detector every 10 years
- Check manufacture date on back
- Combination detectors may have different schedules
Common mistakes
- Only changing the battery when it chirps, which means you're without protection for a period.
- Assuming a hardwired detector never needs a new battery—it does for backup.
- Keeping a detector longer than 10 years because it still sounds when tested.
