A single gas handling system is used to measure CO2 and O2 concurrently in a single contiguous system including both analysers. Air is sampled from an aspirated inlet on the 10 m tower at Weybourne using a diaphragm pump. A two stage drying system is employed and a pressure control interface is used to match the flows of both sample and reference flows upstream of the analyser. All calibrations and outside air measurements are performed against a reference flow of dry cylinder air to improve sensitivity. The CO2 analyser is a Siemens Ultramat 6E non-dispersive infra red (ND-IR) CO2 analyser. After passing through the Siemens CO2 analyser the airstream is analysed for O2 content using an Oxzilla II analyser from Sable Systems that utilises fuel cell technology. The data for both species is reported on the same timestamps.