Silence/test feature to test functions and temporarily quiet unwanted alarms. Unique horn sounds and lights help distinguish between a smoke or CO alarm. Pull out battery drawer for battery replacement. Low battery silence quiets low battery alert withoutaffecting alarm operation. Loud 85-decibel alarm, low battery warning. End of life alarm chirps when it is time to replace detector. 2 AA batteries included. UL listed. 5 year limited warranty.