1)Real time detecting CO2 level,temperature and NDIR infrared CO2 module inside with four CO2 detection range selectable 2)CO2 sensor has self-calibration algorithm and 15years lifetime. 3)Mounted type and duct type selectable 4)Special kind L series with 6 lights indicates CO2level and makes CO2 level clear show 5)Special model with a touch button to operate a fan control 6)Design for HVAC ventilation systems,offices,classrooms or other application places. 7)Providing up to three analog outputs for CO2/temperature/humidity 8)Easy choice of voltage or current via jumpers,0-5VDC/0-10VDC/4-20ma/0-20ma 9)One relay output is available 10)RS-485 communication interface is optional,15KV antistatic protection,independent address setting 11)24VAC/VDC power supply can be connected with the wire teminals,also a power adaptor's plug connected into the socket available 12)CE Approval