Abstract: A vertically oriented, sheet metal enclosure includes a frusto-pyramidal lower section forming a hopper for separated particulate matter from an air stream which enters a middle section from a downwardly and inwardly inclined inlet duct fixed to one side of that section at the upper end, causing impingement of the airborne particles against the side of the hopper to effect a swirling action to the air stream. An array of laterally spaced, inclined baffle plates at the upper end of the middle section separates the middle section from an upper section which carries tensioned tubular filter bags. An enclosure cover defines an outlet opening feeding to a cover mounted blower.