Abstract: Apparatus for filtering particulate matter in a fluid (e.g., gas) and in particular small particulate matter, the apparatus including a rotating filter, an expander or turbine for extracting energy from the fluid after the fluid has passed through the filter, an aerodynamic seal comprising a rotating multiple fin or vane member which rotates with the filter and expander, and depending upon the type of particulate matter, there is provided a spray system or a scrubbing system to aid in filtering the particulate matter.