Abstract: A heat treating furnace including a housing defining a chamber, a heavy high thermal capacity cast link endless conveyor belt positioned within the chamber for moving articles to be heat treated through the chamber, a narrow elongated vestibule passage extending forwardly from the chamber, and a light low thermal capacity wire mesh endless belt conveyor extending from a furnace loading location forwardly of the vestibule passage through the vestibule passage to a location within the chamber in vertically spaced overlying relation to the forward end portion of the cast link conveyor. The vestibule passage minimizes loss of heat treating atmosphere from the furnace chamber, and curtains are provided in the vestibule passage to further minimize atmosphere loss. The light feed conveyor is run at a higher linear speed than the heavy furnace conveyor so that the load on the feed conveyor and the vertical profile of the parts on the feed conveyor may be reduced.