MAJERSKÁ, Kristína: Study of the resistance of spruce wood treated with a retardation preparation to thermal stress. (Thesis). Technical university of Zvolen. Faculty of Wood Science. Department of Chemistry and Chemical Technologies. Thesis supervisor: doc. Ing. Iveta Cabalova, PhD. Degree of professional qualification: Bc. Zvolen, 2020. Scope of work: 51 s.This diploma thesis deals with changes in the properties of spruce wood, which is treated with flame retardant coating Flamgard and then exposed to thermal stress. The work is divided into two parts. The first part describes the theoretical knowledge related to the problem, the characteristics of spruce wood, its properties and a description of flame retardants. The practical part is based on an experiment where samples of spruce wood with the same dimensions were used. These were individually heat stressed for 5, 30 and 45 minutes. The changes in the chemical composition of the wood (extractive calves, lignin, cellulose and hemicelluloses) and the thickness of the charred layer are evaluated.The results of chemical analyzes show that the main chemical components of wood were degraded due to the thermal effect on spruce wood by radiant heating. We recorded the largest changes in the wood sample, which was not treated with a retarding agent. The work shows that the protective agent used significantly reduced the degradation of the material in terms of changes in its chemical composition. Experiments have also confirmed that the least degradable thermally stable components of wood, namely hemicelluloses, have been degraded to the greatest extent.