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.