The First Alert® SMCO100 Battery-Operated 2-in1 Combination Smoke and Carbon Monoxide Alarm provides protection against both threats in a single alarm. Installation of the battery-operated detector is simple - no wiring is required. Add fire and CO protection throughout your home in minutes and help prevent unwanted removal of the battery or alarm using the optional locking features. Easily test the battery-operated combination detector using the single test/silence button to help ensure it is operating properly and silence false alarms. A low-battery warning will tell you when to replace the alarm battery. Detectors themselves should be replaced at least every 10 years. The end-of-life warning will help notify you when it's time to replace. See user's manual for information on how and when to test and replace detectors.