A number of studies of the oxidation of coal using The University of Queensland’s two- metre, 62L test rig have been carried out over the past few years. The rig simulates a semi-adiabatic environment radially and allows gas samples to be taken along its length and from the exhaust stream. This enables the generation of a gas and temperature profile across a coal self-heating zone. As the state of spontaneous combustion in underground coal mines is usually inferred from gas samples taken remote to the heatings these laboratory studies offer important insights into the mechanisms of gas formation during coal self-heating events. In particular much emphasis is placed upon the presence of and concentration of any hydrogen. This paper reports the preliminary findings from a test where such gas samples were taken. The bulk of the hydrogen appears to be generated downstream from the hot spot where the coal is at approximately 100°C and there is no free oxygen.