The Flame Ionisation Detector (FID) on the Greenhouse Gas GC (Perkin Elmer, Clarus 500 Greenhouse GC) at Weybourne Atmospheric Observatory (WAO) is used to make quasi-continuous measurements of methane (CH4) in atmospheric air. Samples are analysed every ten minutes and with reference to the NOAA2004 scale for CH4.The measurements from this instrument are part of the National Centre for Atmospheric Science (NCAS) Atmospheric Measurement Facility (AMF) long-term measurement strategy.