A system for extracting particulates from the exhaust gases flowing from a diesel engine (A) of an automobile by the use of a filter trap (C-1) stationed adjacent a heat controlled zone (43) of the automobile and which system periodically cleanses the filter trap of the collected particulates. The system has an apparatus (20) which channels the flow of exhaust gases between a condition where the exhaust gases carried through the filter trap (C-1) for an extraction mode and a condition where the exhaust gases are diverted away from the filter trap during a cleansing mode of the trap. The apparatus (20) comprises: (a) walls (23) defining a primary flow channel for normally guiding exhaust gases through the filter trap (C-1) housed within the channel, the walls (23) comprises a roof (42) juxtaposed the zone (43); (b) a diversion flow channel (39) for diverting the exhaust gases away from the trap (C-1) during the cleansing mode, the diversion flow channel (39) being superimposed on the roof (42) to normally insulatingly separate the primary flow channel from the zone (43); and (c) a flow diverter valve for directing the flow of exhaust gases through the primary and diversion flow channels. The walls (23) defining the primary flow channel comprise a horizontal tube with an expanding conical inlet section (35). The tube has a cross-section with a height (24) no greater than substantially one-half of its horizontal dimension (25). The top of the tube forms the roof (42). The roof preferably extends horizontally and the diversion flow channel (39) is defined by an inverted U-section wall (40) extending across and attached to the roof (42).