Abstract: An improved assembly for holding a filter element so as to define a filter assembly for removing particulate matter from a sample gas stream. First and second housing sections mount and enclose a replaceable filter element. An annular wall extending between the housing sections divides the interior of the housing into a first region open to an inlet, and a second region open to an outlet, the filter element being mounted in the second region, downstream of the wall. A plurality of openings through the wall assure that particulate matter collects evenly over the surface of the filter element. In this manner, the useful life of the filter element is greatly extended.