Hush® feature ideal to silence nuisance alarm without removing the battery. Never remove the batteries or disable a smoke alarm. Be safe and replace the batteries annually. Ionization Technology: Better at detecting fast flaming fires. Battery Powered: 9V battery included. Easy installation: no wiring required. Test Button: Tests circuitry and verifies alarm operation. Hush® Button: Quickly silences nuisance alarms. Low Battery Indicator: Warning chirp sounds when battery needs replacement. Special mounting bracket included: Allows for fast installation.