The SafeHome GS508 is a battery operated smoke detector which utilizes a photoelectric sensor. Photoelectric technology allows the detector to be more sensitive to detecting slow smoldering fires which generate thick black smoke and little heat. The built in battery that comes with the smoke detector has a minimum lifespan of 10 year. When low on battery, the smoke detector produces a chirping sound as a reminder for replacement. Installation can be done in 2 convenient methods. Either fasten the base of the smoke detector to the ceiling with a screws drilled into the wall, or use the optional magnet with self adhesive on a clean smooth surface