Features: 1) Wall mounting and duct type 2) Carbon dioxide detection and temperature and humidity detection optional 3) NDIR infrared CO2 sesor inside with wide detection ranges selectable 4) CO2 Self-calibration technology 5) 15-year lifetime of CO2 sensor 6) temperature and humidity detetcion optional 7) Providing one/two/three analog output: 0~5VDC/0~10VDC or 4~20mA 8) indicator type with 6 lights for 6 different CO2 level: 2 x green + 2 x yellow + 2 x red lights 9) One relay output is available to control a fan or CO2 generator 10) RS-485 communication interface is optional: 15KV antistatic protection, independent address setting.