First Alert SA320 Battery Powered Smoke Detector with Photoelectric and Ionization Sensors

First Alert SADUAL Dual Sensor Smoke and Fire Alarm (Model SA320) utilizes both ionization and photoelectric smoke sensors for optimal performance - detects both fast flaming and slow smoldering fires. Smart sensing technology helps recognize the difference between non-threatening conditions and real emergencies. Mute bottom serves purpose of quickly silencing alarm and testing it's function. Powered by 2-AA batteries (included) with EZ access battery door - allows you to change batteries without removing the alarm from the ceiling. Meets UL217 standards and backed by 10 year warranty.