An air curtain conveyor protection system that prevents airborne particles from entering a slot (28) through which the product support members (18) extend from the conveyor mechanism housing (25) into the product treatment booth (10). A continuous stream or curtain of high velocity air flows across the slot in the conveyor housing, exiting from an outlet or supply nozzle (45) formed by a plenum (35) on one side of the slot and entering into a suction nozzle (46) formed on the opposite side of the slot by a second plenum (36). A fan or blower (50) is associated with each plenum to force ambient air through the supply nozzle and to draw air through the suction nozzle. Ambient air flowing between the nozzles forms an air curtain across the slot to prevent ingress of the deleterious atmosphere in the product treatment booth into the conveyor housing.