The BRK CO5120BN is a UL 2034 listed 120 volt wire-in carbon monoxide alarm designed for use in residential and institutional settings like hotels, motels, dormitories, and the sleeping rooms of hospitals. It features an advanced electrochemical carbon monoxide sensor, an 85-decibel horn, an easily accessible 9V battery backup, and two locking features that prevent battery theft or theft of the unit. An LED power indicator ensures the unit is always connected to power and an end of life signal provides an audible notice when the alarm needs to be replaced. The unit functions between 40 and 100 degrees Fahrenheit and in humidity up to 95%. The alarm can operate on its own or be connected in a series with up to 18 devices, including smoke alarms, through a “Quick Connect” wiring harness that is easy and cost effective.