Abstract: De-dusting of gases is carried out in an apparatus containing a granular-bed filter, the pourable granular filter medium flowing downward through the bed. The apparatus comprises a vessel of rectangular cross-section with a vertical side wall (4) extending from the top to the bottom. A partition (5), arranged parallel to the side wall (4), extends from the upper end of the vessel into the interior of the vessel. The remaining three side walls of the vessel extend - at least starting from a level corresponding to the lower end of the partition (5), taperingly downward to the outlet (9). The partition (5) is supported by the two walls adjacent to the vertical wall and forms, together with these and with the talus (7) of the filter medium, which arises at the lower end of the partition, a chamber (3) into which the inlet (2) for the gas to be purified opens.