PURPOSE: To prevent choking of a rust powder produced due to oxidation, by a method wherein a number of holes are formed in a flat burner surface, and a metal plate having holes which have diameter slightly larger than that of aforesaid hole and are bored in positions reliably matching those of aforesaid holes at specified intervals is placed on the flat burner to improve the supply of the air.

CONSTITUTION: In a flat burner surface, a number of holes are formed like the discharge ports in a sprinkling can, and a metal plate, having holes, which have diameter slightly larger than those of the holes in the burner and are bored in positions completely matching those of the holes in the burner at specified intervals, is placed on the surface thereof. This constitution causes the improvement of the supply of the air, and eliminates a nozzle type air mixing mechanism to connect the burner directly to a gas pipe. This provides a long life for the gas burner of a gas furnace, eliminates the need for the use, in a constituting member, of a special alloy, and enables the use of a general rust resisting metal.