.~.~ Having exhaust return passage or recirculating fan or jet
(under subclass 159) Apparatus including means by which a portion of the heating gas passing from the work zone of the work chamber is delivered back into the work zone or into combustion material being fed to the chamber.
SEE OR SEARCH THIS CLASS, SUBCLASS:
21, for a process of controlling the flame position or work atmosphere of a heating apparatus including recycling the work atmosphere; and subclasses 144+ for a work chamber having means circulating work atmosphere along or across a path of travel of work from a work inlet to a work outlet.
SEE OR SEARCH CLASS
203+, for refuse incinerators or solid fuel furnaces provided with exhaust gas recirculation means.