A filter housing (60) comprises an inlet for receiving an airflow, a cavity for receiving a filter (70) and an airflow passage between the inlet and the cavity. At least one vane (65a, 65b, 65c), positioned in the airflow passage, partitions the airflow passage into a plurality of ducts (51, 52, 53). The vanes (65a, 65b) lie adjacent to, or contact, the upstream surface of the filter such that each duct (51, 52, 53) communicates with a separate portion of the upstream surface of the filter. The airflow passage extends in a direction which is inclined to the upstream surface of the filter. The vanes (65a, 65b) help more evenly to distribute the flow of air across the surface of the filter and also help to reduce acoustic emissions from the machine of which the filter housing forms part. |