Burning oil shales contribute to CO2 emissions. The spatial distribution pattern shows that these _res occur in areas with moderate or dry climates. This paper investigates the mechanism behind the burning oil shales. The first part includes an overview of the geological setting, Fieldwork results and petrophysical analyses. Based on these settings, we defined a horizontal fractured structure above and below the shale beds and vertical fractures with spacing varying from 10{30 cm. The matrix in between is oil shale with a kerogen content of 35% up to 70 %. The oil shale contains lenses of pyrite. Several dynamic models, based on this fractured oil shale structure, have been developed to illustrate aspects leading to enhancements or extinction of oil shale fires. Natural convection supplies air (oxygen) to sustain combustion. Air can penetrate into the matrix, mainly to the highly fractured structure, to react with fuel. The presence of oxidising pyrite may trigger the fire. Favourable conditions for oil shale fires are dryness, mostly during the summer, and a heat source.