Working smoke alarms cut the risk of dying in a home fire by 50%, and that"s important because a home fire starts every 83 seconds! The faster you know about a fire, the faster you can start moving your family outside. The First Alert smoke alarm with silence button allows you to both silence a non-threatening alarm and to test the unit"s functionality. It features a low battery alert to remind you when to change the battery and has a missing battery guard to ensure that a battery is placed inside the alarm. The side battery drawer slides open for easy battery replacement. A blinking power indicator on the unit confirms that it is receiving power. The alarm contains an optional pin to lock the battery and unit in place for tamper resistance. It can be mounted on either the ceiling or the wall and can be used in mobile homes and RVs. It includes one 9-volt battery and has a 5-year limited warranty. UL listed for safety.--Bree NorlanderWhat"s in the Box One smoke alarm, user"s manual, and one 9-volt battery