There is provided a granular-bed filter for cleaning a gas containing fine particulate matter ("dust"). A multiplicity of vertically disposed filter trays are assembled to form a "panel." In each filter tray, an inclined porous plate supports a bed of granular material. Each bed presents an inclined gas-entry face that receives gas from a vertically-disposed dusty-gas-distribution compartment nearby the face's lower edge. A filter cake forms upon the gas-entry face. Preferably, the bed's depth is substantially the same at its upper and lower edges. Cleaned gas leaves a tray across the porous plate and flows into a vertically-disposed cleaned-gas-collection compartment. After an interval of filtration, gas-entry faces are renewed by producing en masse displacement of the material respecting the supporting plates, the displacement producing a spill of a surface layer from each gas-entry face. The displacement is preferably accomplished by causing the support plates to move sharply upward (e.g., as may be caused by an upward blow of a hammer). The displacement may also be caused by subjecting the panel to a reverse transient surge flow of gas (i.e., a "puff-back"). After face renewal, granular material descends by gravity from an elevated source to make good loss of the material from the faces.