The photoelectric ABUS smoke detector reacts to smoke particles. If too much smoke enters its measuring chamber, a loud alarm signal is triggered. The smoke detector is mounted at the ceiling in the middle of the room. The minimum distance to the side wall is 15 cm, the distance to every corner is at least 50 cm. The capturing range of the smoke detector is up to 40 m high. We recommend installing each one smoke detector in the hall, the stairways, living room and bedroom. The integrated, powerful piezo-alarm sounder provides for an effective alarming in case of a fire - with a volume of at least 85 dB. With the right batteries (9 V lithium) the lifespan is up to 10 years. The battery lifetime varies depending on how often you run the detectors function test. This can be done easily and conveniently via the function test button (recommended: one test every week). A low battery is notified by the detector, issuing regular beep tones. The The home smoke-detector is VdS-certified. This guarantees a high security.