physical safety your priority with this perdurable combination smoke and carbon oxide alarm, with a ten-year product life. This unit equipped with a sealed-in lithium power supply that lasts the uncastrated ten-year life of the alarm and eliminates concerns about battery removal and unauthorised alarm deactivation. It 's and wanton to install alarm automatically activates when attached to the mounting bracket. Smoke alarm photoelectrical sensor that may detect open particles associated with smoldering fires sooner than ionization alarms. a test/hush button that tests alarm circuitry and temporarily silences nuisance alarms. Rapidly LED lights warning signal users if alarm has sounded since the measure time the test/reset button was used. End of life warning alarm every 30 seconds when unit is in need of replacement, but can be silenced three days at a time for 30 days to allow time for replacement. Power : Lithium-Ion Battery Mounting : Ceiling Quantity : 1 each.