Measures Carbon Dioxide (CO?), Air Temperature and Humidity, plus calculates Dew Point and Wet Bulb Automatic Baseline Calibration function Audible High/Low alarm Displays Year, Month, Day, and Time Maintenance free NDIR (non-dispersive infrared) CO? sensor Carbon Dioxide reading displayed in ppm with six facial icons indicating indoor quality levels Calculates Dew Point and Wet Bulb values Calculates statistical weighted averages of TWA (8 hour Time Weighted Average) and STEL (15 minute Short Term Exposure Limit) Specifications Carbon Dioxide 0 to 9,999ppm CFM/P 30 to 1 cmf/p* Relative Humidity Range 0.1 to 99.9%RH IPS 1428 to 51 lps%* Dew point temperature -94 to 140"F (-70 to 60"C) Wet Bulb Temperature 14 to 140"F (-10 to 60"C) Weight 5.8oz (165g) Dimensions 6.1 x 3.4 x 3.2in(155 x 87 x 81mm) Temperature range 14 to 140"F (-10 to 60"C)