NDIR method principal for CO2 ( Carbon dioxide ) measurement available for long term operation. High repeatability and high accuracy. Two probes one is for CO2/temp measurement the other probe is for Humidity/Temperature/Dew point measurement. Separate probe easy operation and convenient for remote measurement. CO2 function with alarm setting. Humidity measurement with fast response time Humidity measurement with fast response time. Data hold function for freezing the desired value on display. Records maximum and minimum readings with recall. Microprocessor circuit assures maximum possible accuracy provides special functions and features.