The CO220 Air quality CO2 monitor measures carbon dioxide, air temperature and humidity. The CO220 also calculates dew point and wet bulb. Use in conference rooms, schools, greenhouses, factories, hotels, hospitals and anywhere that high levels of carbon dioxide are generated. Calculates statistical weighted averages of TWA (8 hour Time Weighted Average) and STEL (15 minute Short Term Exposure Limit). Maintenance free NDIR (non-dispersive infrared) CO2 sensor. Manually store/recall 99 readings. Complete with AC adaptor.