Smoke detector: as soon as smoke reaches the sensor, the detector sounds the alarm. The device can also be used as an independent detector without having to be connected to an alarm system. The sensor is powered by a 6F22 9V battery. The sensor indicates a low battery level. Assembly: The smoke detector is installed in the middle of the room on the ceiling or at lease 1 meter from the wall. The quick-coupling base is screwed onto the ceiling material.