Hardwired smoke and carbon monoxide detector. Interconnectable with AA battery backup. Helps protect you and your family from two hazards - fire and dangerous carbon monoxide (CO) in one unit. This smoke and carbon monoxide detector combo features self-testing components that are always checking to make sure the alarm is on and working. Includes a mounting bracket that makes installation quick and easy. Capable of being hardwired to other select Kidde alarms to provide whole-home alarm activation. This setup allows interconnected Kidde alarms to sound in unison, helping to ensure that everyone in the house is alerted. The photoelectric smoke detector may provide better detection of larger, visible fire particles (the kinds associated with slow smoldering fires).