The REED R9905-KIT is a data-logging indoor air quality meter that simultaneously tracks CO2, temperature, and relative humidity on a triple LCD readout, plus computes time-weighted average and short-term exposure values. This kit adds two humidity calibration standards (33% and 75%) so you can verify and maintain the unit's accuracy in the field. It's well suited for checking HVAC performance and general indoor-air monitoring in offices, schools, and factories.