In recent years, the using of thermally treated wood (thermowood) has expanded. This requires assessing the more thorough impact of the thermal modification of wood on its fire risks. The thesis deals with assessing the impact of thermal treatment of selected coniferous wood on its flammability. The theoretical part is devoted to the synthesis of knowledge in the field of structure, composition, burning of wood and the synthesis of knowledge in the field of thermowood. The subject of the research was selected coniferous woods: Scots pine (Pinus Sylvestris L.), Spruce (Picea Abies) and White fir (Abies alba). The work has a compilation character. The flammability of thermally treated wood was evaluated on the basis of already published fire characteristics of domestic and foreign authors. The obtained results show that the heat treatment has a certain effect on the flammability of the wood. At the mass loss values, this was the negative direction. The thermal treatment had a positive effect on the values of combustion heat. It also had a positive effect on smoke generation, thermal conductivity and the rate of heat release.