Abstract: A closed-loop Regenerative.RTM. air sweeper is provided which constitutes an improvement of that disclosed in U.S. Pat. No. 3,512,206. The sweeper of the latter patent is provided as an integral portion thereof, whereas a conversion, a "dustless" mechanism having first and second chambers into the first chamber of which is directed a portion of the air stream from a pressure conduit associated with a pickup head of the sweeper. Particles of debris are separated by cyclone separators and thereafter by membrane filters after which substantially clean air is discharged to atmosphere. Air entrained particles separated by the cyclone separators and the cartridge filters are returned to a vacuum side of the pickup head thereby maintaining substantially closed-loop air flow of the sweeper. Clean air is controllably exhausted to atmosphere by flue vanes which can be selectively moved under pressure differential sensing means associated with the cyclone separator.