The SD355CO is an addressable combination fire and CO detector that can detect and send separate signals for fire and CO. This multi-criteria detector uses four sensing technologies (photoelectric, infrared, heat, and CO) to accurately detect fire and CO alarm conditions with a high immunity to false alarms. When used with the B200S intelligent sounder base, the SD355CO eliminates the need for multiple devices improving the aesthetics of the protected room and saving installation time and money. Compatible with ES-50X & ES-200X addressable fire alarm control panels.