First Alert, 9V, Photoelectric Smoke Fire Alarm Detector, Provides Maximum Protection, Slim Design, Less Than An Inch Thick, Maximum Protection Alarm Has A Patented Smoke Entry System That Allows A Direct Smoke Path To The Photoelectric Sensor To Detect Regular Slow, Smoldering Fires, Nuisance Free Technology Will Reduce False Alarms That Result From Cooking Shower Steam, Includes Power LED Alarm Indicator, End Of Life Signal Mute Single TestSilence Button So You Can Test Your Alarm Regularly, Installation Is Simple With The Simple Twist Lock Wall Ceiling Mount, Meets UL217 Standards, , NOTE Please Check Your Local Building Code Requirements Before Installing This Product To Determine Compliance With Applicable Standards