Q: How often do I need to replace my hard-wired smoke detectors? And whom should I hire to do this? A few are chirping, and it doesn’t stop even when we replace the batteries.


A: The National Fire Protection Association recommends that you replace detectors when they’re 10 years old.

Security system experts say that, over time, dust gathers inside smoke detectors, desensitizing the sensors. And even if a detector hasn’t reached the 10-year mark, replace it if it chirps after you’ve replaced the battery or if the alarm doesn’t sound when you perform the recommended monthly testing.

Experts recommend replacing all connected detectors at the same time, even if some are working.

You can replace hard-wired detectors yourself, if you can reach them and if you have sufficient skill to replace a light fixture. (Be sure to first turn off electricity at the breaker box.) Or you can hire an electrician or an alarm service company.

Service providers we contacted charge a wide range of prices, from $35 to $40 per detector, plus a $50 for service charge, to $135 to $155 per detector.

The NFPA says interconnected smoke alarms — whether hard-wired or wireless — are best because when one is activated, they all sound. Ionization smoke alarms are quicker to warn of flaming fires. Photoelectric alarms are quicker to warn of smoldering fires. It’s best to use some of both types.