The photoelectrical ABUS smoke detector reacts to smoke particle If too much smoke enters its measuring chamber, a loud alarm signal is triggered. The smoke detector is mounted at the ceiling in the centre of a room. The minimum distance to the walls should be 15 cm, the distance to the corners at least 50 cm The operation range of the smoke detector is up to 40 m. We recommend installing each one smoke detector in the hall, the stairways, living room and bedroom. In the event of fire, the integrated powerful piezo sounder provides an effective alarming at a minimum sound level of 85 dB. When using a 9 V alkaline battery block, the lifetime is up to 3 years (service interval for battery replacement). The battery lifetime varies depending on how often you run the detectors function test. This is done easily by pressing the function test button One test per week is recommended. A low battery is notified by the detector, issuing regular beep tones. The The home smoke detector is GS approved and VdS certified