First Alert, 10 Year, Sealed Battery Operated, Photoelectric Smoke Alarm, With Escape Light, Premium Smoke Detection Capabilities Into A Sleek, Compact Design, For Those Who Want A Reliable Detection System, Uses A Photoelectric Sensor To Detect Smoke From Smoldering Fires While Keeping False Alarms To A Minimum, A Patented Smoke Entry System Allows For A Direct Path To The Photoelectric Smoke Sensor, Helping Ensure Reliable Detection, Comes Equipped With An Ultra Bright LED Escape Light, Which Helps Illuminate An Evacuation Path During Emergencies, Takes Up A Fraction Of The Space Of Traditional Smoke Alarms, Can Be Mounted Unobtrusively On A Wall Or Ceiling, A Loud Alarm Sounds When Smoke Is Detected, Convenient Test/Silence Button Lets You Easily Check Whether Your Alarm Is Functioning.