Extech CO230 Indoor Air Quality CO2 Temperature RH Meter is designed to measure carbon dioxide (CO2), air temperature, and humidity as well as calculate dew point and wet bulb. The Extech CO230 features audible and visual CO2 warning alarms when CO2 exceeds high or low user set levels, MIN/MAX values for CO2, desk or wall mounting, automatic baseline calibration (ABC) with a disable feature for use in areas with continuously elevating CO2 levels, and more.