Combining premium smoke detection with a sleek, compact design, the First Alert Micro Photoelectric Smoke Alarm with 10-Year Battery delivers the same advanced protection as a traditional alarm while taking up only a fraction of the space. This smoke detector uses an ultra-reliable photoelectric sensor to detect smoke from smoldering fires while keeping false alarms to a minimum. A built-in 10-year lithium-ion battery provides continuous power, with no need to ever worry about changing batteries during the lifetime of the alarm. Much smaller than an ordinary smoke detector, this unit is manufactured using 52 percent less resin and 76 percent less plastic than a standard alarm. The SmartClip mounting system allows you to effortlessly install the detector on a wall or ceiling. A loud 85-decibel siren sounds if smoke is detected, and a convenient test/silence button lets you easily check alarm function and mute false alarms.