The Smartwares RM218/3 10 years will sound the alarm when they detect smoke in your home. This package consists of 3 smoke detectors that work independently. The loud, high-pitched, 85-decibel audio signal will get your attention immediately when the smoke detectors go off. The smoke detector runs on a 3V battery, which lasts about 10 years. Mount the smoke detectors to the ceiling using the included screws. Regularly check the smoke detectors using the test button. This way, you're sure that they're functioning properly.