The Extech CO230 Meter Measures Carbon Dioxide (CO2), Air Temperature and Humidity, plus calculates Dew Point and Wet Bulb. The CO230 Features Automatic Baseline Calibration (ABC) with disable for use in areas with continuously elevated CO2 levels. The Extech CO230's alarm function with user settable high/low CO2 level is perfect for monitoring air quality and ensuring proper air ventilation in conference rooms, schools, greenhouses, factories, hotels, hospitals and anywhere that high levels of carbon dioxide are generated.