PURPOSE: To suppress backfiring by forming layers wherein no oxidation catalysts are deposited beforehand on the inflow side for gaseous mixtures thereby creating low temp. areas where the rate of oxidation reaction in said parts is decreased.

CONSTITUTION: Structural bodies 1 of a heat resistant inorg. material are dipped in an aceton soln. of a vinyl acetate polymer of low degrees of polymn. having a controlled concn. from the side (a) to be impregated with the aceton soln. of vinyl acetate up to prescribed widths aWb. The acetone of the solvent is evaporated and dried by hot wind, thereby forming vinyl acetate films on the surfaces between the aWb and the inside surfaces of small holes 2. The bodies 1 are dipped from the side c into a mixed soln. of alumina sol, zirconia, chloroplatinic acid to to absorb and stick the soln. thoroughly between bWc. Such bodies are left standing at a room temp. so as to be allowed to dry gradually. After the drying the bodies are fired in an atmosphere of 100°C to burn away the vinyl acetate between the aWthe b, and to deposit oxidation catalysts on the alumina and zirconia between the bWthe c.