The First Alert(R) battery operated ionization smoke alarm is equipped with a9 V battery that ensures its operation during a power failure. This alarm that boasts a bright escape light that illuminates a path to safety when the alarm sounds. This is extremely useful when dealing with smouldering fires that can fill the home with thick smoke. The alarm also has a mute button to silence any unnecessary alarms caused by cooking smoke or shower steam. The alarm provides an easy access door for the battery with no need to remove it from the ceiling when changing batteries. This product is backed by a 10-year limited warranty.