Advanced Sensor Technology: photoelectric sensor technology provides advanced smoke detection in sensing visible fire particles associated with smoldering fires to reliably detect smoke or fire hazards Reduces Nuisance Alarms: sensor technology reduces false alarms often caused by cooking or shower steam Self-Testing Alarms: internal components ensure alarm is always operating as expected. Self-testing is not a substitute for a manual push test of the alarm. Perform a button test once per week to verify proper alarm operation. Peace of Mind: the Kidde battery-operated smoke alarm provides coverage during power outages Early Warning Detection: upon sensing smoke or fire, an 85-decibel alarm sounds & a red LED will illuminate Ideal for Small Spaces: compact 4-inch design fits in tight spaces No Wiring Needed: operates on 2-AA alkaline batteries (included) providing easy installation, simply mount the bracket onto the ceiling and twist & click the smoke alarm into the bracket Battery Replacement: a low battery chirp alerts you when batteries need replacing End-of-Life Alarm: alarm sounds as a reminder when it is time to replace the alarm after 10 years of use after its original power-up date Test-Hush button makes it easy to test the smoke detector and silence false alarms, should they occur Rigorously tested by ETL to meet UL 217 10th Edition and FCC standards for performance and safety