The Extech EA80 checks carbon dioxide concentrations with a maintenance-free dual-wavelength NDIR (non-dispersive infrared) CO2 sensor with a range of 0 to 6,000 PPM. This can automatically log up to 20,000 records or up to 99 records can be manually entered for later retrieval. Other functions include automatic switch-off, measured value memory, max/min value with time stamp and alarm.