The most common in the production of fibrous thermal insulation using fine raw materials (up to 10‒15 mm) or fragile easily crumbling rocks are bath furnaces. Their operation at horseshoe-like movement of gases in working space is characterized by considerable unevenness of temperature field of liquid bath due to limited range of gas flares. The combustion of natural gas in the working space of the furnace is carried out with a high coefficient of air consumption with the complete absence of chemical malaise. As flue gases are transported from the regenerator to the pipe, the number of suckers increases by 44,85 %. The exhaust gases from the regenerator are characterized by a relatively high temperature of 570‒600 °C and a significant heat reserve up to 2022,09 kW, which requires their further disposal. The thermal efficiency of the regenerative furnace bath is 39,04 %.