The invention relates to a filtering device for a variety of polluted gasses, with an inclined bed with a filling of catalytic material, which bed has a retaining wall at its lower longer side, with a clean-gas exit positioned in the area of one front side of the bed, which ejects the gas which has passed through the filling, and with a flush-gas entrance also positioned in the area of one front side of the bed, the flush-gas entrance (40) and the clean-gas exit (36) being provided at the same front side (38), and beneath the bed (12), current-influencing devices (50) being positioned spread between the two front sides, which devices prevent or at least reduce current peaks in the flow of flush gas through the bed (12).