Quasi-continuous measurements of molecular hydrogen (H2) and carbon monoxide (CO) in atmospheric air. Measurements are made using a modified commercial Reduction Gas Analyser (RGA3, Trace Analytical, Inc., California, USA), which includes gas chromatography followed by the reduction of mercuric oxide. Mercury vapour from this reaction was detected by UV absorption. Samples are analysed every six minutes and with reference to the MPI2009 scale and the NOAA2004 scale for H2 and CO, respectively.

Data files containing the H2 and CO data are submitted on a monthly basis to BADC using the NASA AMES variable naming convention.