Extech CO210 Air Quality Carbon Dioxide Data Logger Checks for Carbon Dioxide (CO2) concentrations User-adjustable high/low alarms Maintenance free NDIR (non-dispersive infrared) CO2 sensor Indoor Air Quality displayed in ppm with Good (0 to 800ppm), Normal (800 to 1200ppm), Poor (&gt;1200ppm) indication Datalogs up to 5333 points of each parameter