The First Alert 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. Sometimes a fire can smolder for hours before erupting into flames. Photoelectric-sensing technology is more sensitive than ionization-sensing technology at detecting these sorts of smoldering fires, like those caused by cigarettes burning in couches or bedding. Other fires erupt into flames quickly, like kitchen grease fires or fires fueled by paper burning in a wastebasket. Ionization-sensing technology is generally more sensitive in detecting these sorts of 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. The First Alert SA3210 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.