Abstract: Apparatus for attenuating particulate matter and volatile organic compounds in exhaust gases of diesel engines. The apparatus includes a housing disposed serially relative to exhaust gas flow. The housing encloses mechanical filters having gas orifices of different sizes, and after the filters, a low temperature, low restriction catalytic converter. Pressure may be monitored to infer clogging by particulates. Clogging may be annunciated by an indicating light. Individual filters may be contained within plural separate filter canisters, which may be removed for cleaning. The housing may be substantially of aluminum, having cooling fins and a longitudinally oriented mounting foot. Filters may be arranged such that their orifices are misaligned to promote separation of particulates from the exhaust gases.