The First Alert SA720CN Photoelectric Sensor Smoke Alarm is equipped with special technology that helps to increase its accuracy. A mute feature silences nuisance signals. A single button also tests alert functions. This item features an easy-access battery drawer so there is no need to remove it from the ceiling to change the battery. The First Alert smoke alarm features an optional theft-prevention lock. When this feature is activated, the batteries and alarm cannot be removed without proper tools. This product is Eco-friendly and completely recyclable as an electronic device. The battery-operated smoke alarm comes with a 9V battery, making it all the more convenient.