An improved oven (1) comprising a conveyor configured and arranged to move a product (11) to be processed through an oven, a primary air delivery system (45) configured and arranged to provide a heated primary air flow (47), a secondary air delivery system configured and arranged to provide a heated secondary air flow (48), a processing enclosure (21) configured and arranged to receive and contain the product and the primary air flow, an insulated enclosure (2) configured and arranged to receive the heated secondary air flow, the processing enclosure configured and arranged to extend through the insulated enclosure and the heated secondary air flow and to separate the primary air flow from the secondary air flow.