The Kidde 900-0284 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 alarm includes both night light and escape light features. The brightness of the night light can be adjusted to ten different levels by pushing the peak level button, or turned off if needed. The ambient light sensor will automatically turn the night light on or off depending on ambient light conditions, when connected to AC power. The escape light feature will brightly illuminate during alarm mode, helping those present to exit during dark conditions and when electrical power outages occur. 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.