Abstract: Apparatus is disclosed for attachment adjacent an open end of a rotary furnace, having a first effluent furnace gas exhaust duct projecting into the furnace and a dust collecting hood adjacent the furnace opening. A pressurized air duct plenum having a plurality of air jet holes directs a curtain of air across the furnace open end, and a receiving air duct plenum having a plurality of openings collects the air curtain for exhausting via a filter system. The hot effluent furnace gas is passed through a gas to gas heat exchanger and to the aforementioned filter system.