Keep your family safe without the hassle of battery-replacement and maintenance. The sealed-in battery keeps this carbon monoxide alarm functioning for ten years without the need for replacement. Easy to install alarm automatically activates when attached to the mounting bracket. Test/reset button tests unit for proper operation and resets carbon monoxide alarm. Green LED flashes every 30 seconds, indicating unit is operating properly. Red LED will pulse and a loud alarm pattern will sound when a dangerous level of carbon monoxide is detected. Red LED will also flash every 60 seconds if a high level of carbon monoxide has been detected within 14 days. Alarm(s): 85 dB at 10 ft; Sensors: Electrochemical; Size: 4.5 x 1.5 x 2.75; Power Source(s): Lithium-Ion Battery.