The First Alert SMCO500V Interconnect Battery-Operated Combination Smoke and Carbon Monoxide (CO) Alarm with Voice and Location Alerts helps provide an early warning and guide your escape to safety. This combo detector is also equipped with First Alert's Precision Detection advanced sensing technology that meets the latest industry standards.The SMCO500V Interconnect Combination Smoke and CO Alarm with Voice and Location Alerts is battery-operated making installation simple. Equipped with premium and convenient safety features like a one-touch test/silence button and optional locking features to prevent unwanted removal of the detector or batteries. The low battery and end-of-like warnings will help notify you when it's time to replace the batteries and alarm itself. See user's manual for information on how and when to test and replace detectors.