AA batteries required (best with Polaroid AA batteries) Two sensors detect smoke from both smoldering and flaming fires. Engineered to reduce false alarms from cooking smoke or steam Loud 85-decibel alarm is designed to be heard easily and mute button, mutes unnecessary alarms immediately. Also tests alarm function with same button Single test/silence button for simple operation Battery-powered fire detector installs easily with no wiring required The First Alert SA320CN Dual-Sensor Smoke and Fire Alarm is an advanced smoke detector that uses ionization and photoelectric sensors to provide early warning of both smoldering and flaming fires. It also features intelligent sensing technology to reduce false alarms from household triggers like cooking smoke or shower steam. The battery-powered fire detector installs quickly and easily, with no wiring or electrician required. A loud 85-decibel siren is designed to alert even the soundest of sleepers, and a single button silences and tests the fire detector.