Abstract: A method of cleaning flow structure within a regenerative fume incinerator of the type having a plurality of heat exchange chambers for directing fluid into and out of a combustion chamber. Each of the heat exchange chambers have a separate inlet and outlet line which are cyclically opened such that air to be cleaned is continuously being directed into the combustion chamber through one of the chambers, and cleaned air is continuously directed out of the combustion chamber through an alternative one of the chambers. The flow structure, valves and manifolds may become clogged with residue from the air being combusted. An alternate inlet line communicates from the source of fluid directly into the combustion chamber. That line is opened when cleaning of the flow structure is desired. At the same time flow to the normal inlet manifold is closed.