The Kidde 900-0280 AC Powered, Plug-in carbon monoxide alarm with sealed lithium battery backup and digital display is an easy to install unit that provides reliable protection against the dangers of carbon monoxide. The 10-year* sealed battery offers protection during power outages, prevents unwarranted removal of the battery, and eliminates the need for annual battery replacement. The digital display feature adds an advanced level of protection showing CO levels in PPM allowing you to see if levels change. This display uses LED technology which allows the CO levels to be visible in dark conditions and further distances than other alarms that use less visible LCD components. The display will automatically adjust brightness level to adapt to ambient light conditions, which offers both a brighter display during lighted environments and dims to provide a visible, but softer contrast at night. The display deactivates when AC power is removed to conserve battery life.