Abstract
The article verified the conformity of the gradation of coal seams into three groups according to their endogenous fire hazard, according to regulatory documents, with the actual conditions of accidents that have occurred over the past twenty years during the development of 66 coal seams of the Donetsk basin. The degree of metamorphism of coals of the considered coal seams, where endogenous fires occurred or they were absent, was estimated in terms of the release of volatile matters index during their thermal decomposition without air access (Vdaf).