The main reasons for temperature increase and tendency of coals to spontaneous combustion in the natural state and after the technogenic impact have been considered. Attention is drawn to the influence of the deformation and destruction energy in the conditions of mountain pressure on the additional increase in temperature, as well as on the influence of fractal properties of fractured coal on the physico-chemical processes, which contribute to the increase in temperature. The influence of fractal properties of fractured coal on the intensity of physico-chemical processes has been verified experimentally. In experiments on drying and weight control after being in the air, coal fractions of 10 to 0,2 mm and less were investi­gated. It has been established in the experiments that the fractal properties of the destroyed experimental material are ensured during crushing in a ball mill and are breached during crushing in a jaw crusher. The main result of the research: – fires of self-ignition are confined to clusters of fractions of micron and submicron scale, which have fractal properties; – processes of deformation and destruction of coal in the massif and the pillars are an additional factor in temperature increase.