First Alert 10-Year Battery Dual Sensing Smoke Alarm Dual-sensor smoke and fire alarm with 10-year sealed battery makes use of both ionization and photoelectric sensors to offer the earliest possible warning, regardless of the type of fire. Photoelectric-sensing technology is more sensitive than ionization-sensing technology at detecting smoldering fires, like those caused by cigarettes burning in couches or bedding. Ionization-sensing technology is generally more sensitive in detecting flaming fires. A single test/silence button mutes unnecessary alarms and tests function. The end-of-life timer sounds when it's time to replace your alarm. Meets UL217 standards and complies with legislative requirements for 10-year battery-operated smoke alarms. This product includes mounting hardware and is backed by a 10-year limited warranty. Type Battery Operated, Voltage 3V, Battery Life 10 Yr. Battery, Sensor Type Photoelectric/Ionization, Dimensions 5 In. W. x 2 In. H. x 5 In. L., Battery Back-up Battery Only, Alarm Type Smoke, Decibel Level 85dB, Battery Type 3V Lithium Battery, Batteries Included Yes, Color White, UL Listed Yes, Warranty 10-Year Limited, Pkg Qty 1, Package Type Clamshell