This kidde home protect smoke alarm uses optical sensor technology and is ideal for use in living areas powered by a sealed in 10 year lithium battery that lasts the full life of the alarm and never needs replacing when activated the alarm has a loud 85 decibel alert it is simple and easy to install thanks to its single screw mounting bracket with a hush button feature that lets you silence nuisance alarms and a test button with led for simple verification of continual battery and alarm operatio