A fabric filter (1) has at least a first compartment (2) and a second compartment (4). A hopper (42) is adapted for fluidisation of dust collected in the compartments (2, 4) to form a bed (52) of fluidised dust. A partition wall (62) is located between the compartments (2, 4) to separate them from each other. A passage (68) is formed at a lower end (66) of the partition wall (62) such that fluidised dust may pass through said passage (68). The partition wall (62) is arranged to extend into the bed (52) of fluidised dust for forming a seal (74) even when one of the compartments (2, 4) has been shut off. When shutting off a compartment (4) the inlets and outlets to that compartment (4) are closed and the dust in the hopper (42) is fluidised to provide a seal (74) between the compartments (2, 4).