Abstract: A filter assembly useful in collecting the particulate matter from a diesel engine onto surfaces on which the combustion vapors are condensed, and thereafter exposing the exhaust stream to catalytic reaction, is defined by a split cavity in which a row of kinematic filter discs is received. The filter discs are stacked in the assembly in a progressively finer opening size, each filter disc making an intimate contact with the assembly housing for cooling. In this manner condensation onto the discs is promoted to provide a liquid bed on which the particulate matter is trapped. The exhaust flow then passes through a coiled, corrugated catalyst surface for further reaction. A set of spring loaded bypass conduits is provided to allow diesel operation at such times when the filter plates and the catalytic coiled surface are clogged. The filter plates and the coiled catalyst strip can then be periodically removed and cleaned, for continued operation.