Double the Detection: photoelectric sensor technology provides advanced smoke detection in sensing visible fire particles associated with smoldering fires to reliably detect smoke & fire hazards, while an electrochemical sensor reliably detects poisonous carbon monoxide gas 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: operates on a 120-Volt AC wire (installed in your ceiling) with two AA alkaline batteries that provide battery backup coverage during power outages Early Warning Detection: upon sensing smoke, fire or carbon monoxide, an 85-decibel alarm sounds & a red LED will illuminate 3 LED Indicators: illuminate based on status of smoke & carbon monoxide alarm: green = operating properly, amber = fault in operation or error, red = smoke, fire, or carbon monoxide indicated Easy Installation: simply mount the bracket onto the ceiling, connect the wires installed in your ceiling to the Kidde Smoke & Carbon Monoxide Alarm, 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 & carbon monoxide detector and silence false alarms, should they occur Whole-Home Connection: ability to connect alarms, so when one alarm sounds, they all sound, so you never miss an emergency & can escape quickly. Not all models offer interconnection or Whole-Home Connection options and requirements. Check each models user guide for more details. UL Listed: comprehensively tested to meet requirements of UL 217 9th Edition, UL2034 4th Edition, FCC, CSFM, and California Prop 65 standards