NAPCO 12/24V CARBON MONOXIDE DETECTORNapco FW-CO1224 – 12/24 VDC Carbon Monoxide Detector – The first commercially available gas sensor that uses patented biometric technology to simulate CO gas level response in the human blood stream for immunity to false alarms from common household gases.Independent lab tests prove superior false alarm immunity over electrochemical. These CO alarms are suited for residences, motels, hotels, and commercial or industrial system applications. The FW-CO12 is designed for 4-6 wire connection to 12VDC alarm system control panels. The FW-CO1224 is designed for 4-6 wire connection to 12 or 24VDC alarm system control panels. Reference: UL Listed Household Fire and/or Burglary Panel with auxiliary signaling zones. Connect to signaling zones which can be designated for CO alarm use only.