Abstract: A continuously cleaned bag filter provides a second filter stage for removing dust from air discharged from a cyclone or other primary separator. The primary separator removes the majority of particulate matter from air delivered thereto. In the bag filter dust is filtered from the air, which is discharged through the filter walls. The filtered dust is conveyed along the bottom of the bag filter by an air conveyor and is recirculated back to the primary separator for removal thereat. The air conveyor and a recirculating air blower, the latter providing impetus to carry dust back to the primary separator, are balanced relative to the inflowing air to the bag filter from the primary separator; such balance prevents excessive back-pressure or negative pressure in the filter bags that would otherwise interfere with ordinary air discharge therefrom.