The BRK CO5120BN hardwire carbon monoxide alarm detects dangerous CO gas and allows you peace of mind with its battery backup. Carbon monoxide (CO) is a colorless, odorless, deadly gas. It can be emitted by sources including gas or oil furnaces, gas clothes dryers, water heaters, fireplaces, wood stoves, charcoal grills, gas ranges, and space heaters. A clogged chimney, improper venting, and attached garages can also cause carbon monoxide accumulation. According to the Consumer Product Safety Commission (CPSC), at least one CO alarm should be installed near a home's sleeping area. This BRK alarm is perfect for bedrooms, as well as hallways, and basements.