First Alert, Dual Sensor Smoke Fire Alarm, Offers Comprehensive Monitoring For Smoke By Using 2 Different Sensors, A Single Button Silences The Alarm Tests The Unit, While A Loud 85 Decibel Siren Is Designed To Alert Even The Soundest Of Sleepers, Battery Powered Design Allows The Fire Detector To Be Installed Easily, IonizationPhotoelectric Sensor Type, NOTE Please Check Your Local Building Code Requirements Before Installing This Product To Determine Compliance With Applicable Standards