A LI-COR LI-7500 open path gas analyser has been deployed at the Chilbolton Facility for Atmospheric and Radio Research site in Chilbolton, Hampshire. The instrument operates at infra-red wavelengths measuring the absorption due to carbon dioxide and water vapour at specific wavelengths along its 0.125m measurement path. Internally-stored calibration data are used to convert these absorption values to a mole concentration for each gas. Carbon dioxde and water vapour mole concentrations from this instrument are also provided with sonic anemomenter data at a 20Hz data acquisition rate for eddy covariance calculations in another CFARR dataset. Measurements are taken at 10s intervals.