PURPOSE: To prevent the diffusion of oxygen contained in the atmosphere into gaseous hydrogen and to diminish the usage of gaseous hydrogen and also to obtain a gaseous hydrogen atomospheric furnace elevated in safety by introducing an inert gas wherein the density is made small by means of heating to the skirt part of the gaseous hydrogen atmospheric furnace.

CONSTITUTION: An inner cylinder 4 of furnace is heated 3 at the brazing or heat-treating temp. and gaseous high-purity hydrogen is introduced 5 into the inside of the inner cylinder 4 and filled therein. The material 6 to be treated is sent to the heating region of the inside of the furnace with a mounting stand 7 and heated in the gaseous high- purity hydrogen and gaseous hydrogen is discharged to the atmosphere through the skirt part of the furnace core and diffused. Gaseous hydrogen and an air layer 10 are separated without increasing the flow rate of gaseous hydrogen by supplying gaseous nitrogen between the heating region and a discharge port of spent gas all the while. Further, since the weight of gaseous nitrogen becomes about 1/2 by heating gaseous nitrogen, for example, till about 3,000°C and becomes the intermediate weight of air and gaseous hydrogen, gaseous nitrogen layer is formed in the intermediate part between gaseous hydrogen and the air layer. Therefore, the shielding effect of the gaseous hydrogen flow 8 and the atmosphere 10 is exhibited and thereby the direct diffusion of both can be prevented.