A method for renewing a sheet-type filtering material to a flowing gas stream inside a conduit by converting some of the energy of a flowing gas stream traversing the filter assembly to rotate a propeller and the propeller shaft. The rotational energy from the propeller shaft is operably coupled to a gear that causes a supply of unused sheet-type filter material on a first side of the filter assembly top move across the filter assembly to a second side of the filter assembly, so that the portion of the sheet-type filtering material in a position to filter a flowing gas stream changes over time as the flowing gas stream rotates the propeller.