The Kidde Battery Operated Photoelectric Smoke & Carbon Monoxide Detector with Hush Feature and Voice Alerts, model 900-CUDR-V, is a smoke alarm and carbon monoxide detector combo that operates on 2-AA batteries (included) and is equipped with self-testing components that are always checking the unit to ensure the device is operating as expected*. The Whole-Home Activation features expand via the hardwired 120V AC connections to other Kidde smoke alarm, so when one alarm sounds, they all do**. Upon a smoke or carbon monoxide event, an 85-decibel alarm & voice alert will state, "Fire! Fire!" or "Warning: Carbon Monoxide." The combination smoke & carbon monoxide detector also provides a voice alert of "Low Battery" when the battery on the unit needs to be replaced. LED warning light indicators will also alert to statuses: green light indicates normal operation, amber light indicates an operating error, and the red light indicates a smoke, fire, or carbon monoxide event. The Kidde Smoke & Carbon Monoxide alarm uses photoelectric sensors that detect visible fire particles associated with slow smoldering fires, as well as electrochemical sensors, which offer accurate readings of CO presence. The alarm will also begin to chirp when the battery is reaching the end of its life. When a nuisance, or ?false,? alarm sounds from things like routine cooking or shower steam, the Hush feature temporarily silences this Kidde smoke & carbon monoxide detector. Install a smoke detector and carbon monoxide detector on each level of your home, in hallways, and inside each bedroom. UL Certified with a 10-year limited warranty on the alarm. Meets requirements of UL 2034, UL217, NFPA72, NFPA 101, FHA, & HUD. *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. **Alarms only connect with select Kidde alarms that have hardwired AC interconnect capability (see User Guide).