The Extech CO230 measures carbon dioxide (CO₂), air temperature, and humidity. It features automatic baseline calibration (ABC) with disable for use in areas with continuously elevated CO2 levels. Its 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. The CO230 also calculates dew point and wet bulb values, min/max CO2 value recall, and statistical weighted averages of TWA (eight hour time weighted average) and STEL (15 minute short term exposure limit). Alarm relay output for ventilation control and wall mount. Complete with Universal AC adaptor and multiple plug types (US, EU, UK, AUS).