Research on partially oxidized coal helps in the early detection of spontaneous combustion due to secondary oxidation of the coal remaining in mined-out areas. Three types of coal samples were used in this study. A self-designed temperature-programmable experimental system was developed to investigate the spontaneous combustion characteristics of partially oxidized coal. In addition, the differences between the oxidation characteristics of a fresh and a partially oxidized coal sample were studied. The CO concentration and its production rate, the oxygen consumption rate and the heat release rate were used as macro-characteristic parameters to show the oxidation characteristics. The results show that the characteristic parameters increased faster with temperature for partially oxidized coal compared to a fresh sample up to a temperature of 110-140 degrees C. Above this temperature the opposite is observed. (C) 2016 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.