Thermowood is a material whose importance and production has been growing recently, especially due to its positive properties and ecological production technology. Therefore, it is necessary to focus in more detail on its fire protection and safety characteristics. The aim of the diploma thesis was to find out the influence of thermal treatment on selected fire characteristics of wood samples of the Scots pine and the Sessile oak. Wood, its structure, chemical and elementary composition, physical, mechanical and fire-technical properties are characterized in the theoretical part. Also, in this section are specified the woods of the Scots pine and Sessile oak and attention was paid to the relationship of wood to fire. The experimental part deals with the determination of the gloss calorific value and net calorific value based on the STN ISO 1928 standard by means of the calorimetric device IKA C 5000 control and the measurement of the linear rate of burning by a non-standard method. The measurements were carried out on samples of selected woods which were dried to absolute dry condition and then thermally treated at 160 ° C and 200 ° C for 3 hours and 9 hours, with one set of samples left without thermal treatment. When determining the gloss calorific value and calculating the net calorific value, it was found that for samples of Scots pine, the gloss calorific value and net calorific value decreased with increasing temperature and time of thermal treatment. In Sessile oak samples, the gloss calorific value and net calorific value increased with increasing temperature and thermal treatment time. When measuring the linear rate of burning, we found that for Scots pine samples the linear rate of burning was higher for samples without thermal treatment. No significant change in linear rate of burning between samples with different thermal treatments was observed for the Sessile oak samples.