FCD3NCN CARBON MONOXIDE DETECTOR | The First Alert CO400 carbon monoxide alarm utilizes a electrochemical carbon monoxide sensor that lasts for up to five years to detect carbon monoxide. This carbon monoxide detector is battery powered, making it portable and easy-to-use anywhere, even in the event of a power outage. When carbon monoxide levels become elevated, a loud 85 dB alarm alerts you to the threat.