In a filtration system, in particular for cleaning the intake air of a gas turbine, including a flow channel surrounded by walls with an inflow opening and an outflow opening, a partition wall with at least two openings between a dirty side and a clean side which is positioned between the inflow opening and the outflow opening and limited by the walls of the flow channel, and at least two filters for purifying a flowing fluid. At least one filter is installed at a first opening on the dirty side of the partition wall and at least one filter at a second opening on the clean side of the partition wall.