Coal, a flammable substance, is affected by spontaneous weathering and can be hazardous when exposed to thermally unstable conditions. Over the past few decades, numerous chemical disasters involving coal have occurred, resulting in many deaths. Therefore, strategies for the prevention of such disasters must be implemented to ensure human safety, avoid financial losses, and minimise adverse environmental effects. This study determined the thermal safety parameters and thermal hazards of lignitous and long flame coal by using thermogravimetry and differential scanning calorimetry. The characteristics of the functional groups in coal and treated coal were observed through Fourier transform infrared spectrometry. The structures of coal and coal treated with an ionic liquid, namely 1-butyl-3-methylimidazolium, were observed through scanning electron microscopy. Finally, theoretical kinetic models were applied to calculate thermokinetic parameters and identify the degree of thermal hazard present during periods of thermal instability. The results revealed that 1-butyl-3-methylimidazolium nitrate considerably reduced the probability of coal spontaneous combustion and the degree of hazard for long flame coal. Therefore, this ionic liquid could serve as an effective inhibitor of spontaneous combustion in long flame coal. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.