State of the art smoke and CO combination alarm designed to provide early warning of a fire or carbon monoxide danger. Has a photoelectric smoke sensing chamber and an electrochemical CO sensor. Features a sweeping horn tone that has a lower and varying frequency that makes it easier for the elderly with normal age related hearing loss to hear the horn. Optipath 360 technology provides 360 degrees of direct access to the smoke sensing chamber. Operates between 40F (4C) and 100 degreesF (38 degreesC) and relative humidity between 10 and 95 percent. Silence/test feature to test functions and temporarily quiet unwanted alarms. Unique horn sounds and lights help distinguish between a smoke or CO alarm. Pull out locking battery drawer for battery replacement. Pins are provided to lock battery drawer and/or alarm to base. Low battery silence quiets low battery alert without affecting alarm operation. Loud 85-decibel alarm, low battery warning. End of life alarm chirps when it is time to replace detector. 2 AA batteries included. Designed for wall or ceiling mounting. Includes mounting anchors and screws. UL listed. 7-year limited warranty.