The diploma thesis deals with the development of temperature on the surface and in the body of spruce wood samples, which were protected by flame retardant. Further, in our work we evaluated the thickness of the char and the depth of burning, which we measured according to the NFPA 921 guide. Overall, our work is focused to the protection of the surface of wood materials to improve the fire-technical properties of wood. Measurements were performed by a non-standard exam, which was determined by the supervisor of the diploma thesis. All measurements were performed in the laboratory of the Department of Fire Protection. The results confirmed the efficiency and effectiveness of the fire retardant, which increased fire resistance of wood. The results can be applied to assess the efficiency of retarders and to project fire protection measures for wood buildings