KACO2 sensor reliably detects the concentration of CO2 in the air ducts in the range 0-2000ppm or 0-5000ppm to choose. Measurement results can be displayed via the Modbus. CO2 level measurement is performed by means of NDIR-sensor that works on infrared basis and using a double-beam measuring principle compensates different pollution. Optionally, the sensor can be purchased with an optional module for measuring temperature and humidity.