The First Alert Dual-Sensor Smoke and Fire Alarm with 10-Year Sealed Battery makes use of both ionization and photoelectric sensors to alert you to danger in your home as early as possible, even if it’s a smoldering fire. A single test/silence button mutes unnecessary alarms and tests function, while an end-of-life timer sounds when it’s time to replace your alarm. The 10-year lithium-ion battery provides continuous power for up to a decade, and the alarm requires no hardwiring for installation. The First Alert SA3210 meets UL217 standards and complies with legislative requirements for 10-year battery-operated smoke alarms. It is recommended that you install a Smoke Alarm in all rooms, halls, storage areas, finished attics, and basements, where temperatures normally remain between 40 F (4.4 C) and 100F (37.8 C).