The results are presented concerning the experimental studies of the behavior of fire-retardant seals produced by the Ogneza group of companies under thermal exposure up to 1000 °C, obtained by the method of synchronous thermal analysis (thermogravimetry together with the differential scanning calorimetry). Incombustible properties of the M-СORE (NG) seal were confirmed, which showed a decrease in the mass of the material when heated to 1000 °C by 11%, which is due to the mineral composition of the sample (a silica-based material). High thermal stability was shown by the fire-fighting seal M-CORE, the decrease in the mass of the sample of which, after reaching a temperature of 555 °C, stops at 37 %, which indicates the formation of an ash residue. Thermal sealing tape LTU, as a result of the temperature heating starting from a mark of 192 °C, uniformly was losing mass up to a total value of 82 %. The experiment established the sealant swelling. According to the experimental data obtained, the samples M-CORE (NG) confirmed the fire-retardant properties declared by the manufacturer. For the selection of heat-resistant materials that can withstand significant temperature loads during the operation of units and mechanisms, for electrical and thermal insulation, for fire protection of air ducts, equipment, structures, the advantages, and reliability of these seals are obvious. The results of the study (the temperature of the beginning of an intensive decrease in mass, the temperature of the onset of thermal effects accompanying a decrease in mass, the behavior of materials under thermal exposure) can be considered when designing heat and electrical insulation, fire protection of production processes, as well as when determining the level of fire risk of the production facilities.