Abstract: A furnace of autoclave for heat treatment of carbon articles impregnated with a fluid medium, which is provided with a smoke-elimination system including means for supplying clean air under pressure to the closed furnace and exhausting said air through a smoke incinerator or other cleaning means, and means for supplying clean air by suction to the top of the open furnace and exhausting said air through the same cleaning means. Valves are provided to control the admission and draining off of the fluid medium and to determine the course of flow of the air in order to carry out the method of operation.