A filter assembly for the filtration of a liquid or gaseous substance comprising a frame and a plurality of filter members fitted in the frame in parallel relation to one another. Each filter member consists of two elements connected together to form a hollow interior, the substance to be filtered being introduced at one side of the filter and passing through the hollow interior and then through the filter elements for discharge between adjacent filter elements of adjoining filter memers. Each filter element comprises a layer of fiber glass and at least one fleece layer, the two layers being connected by needle felting together at locations between the connections of the filter elements constituting the filter member.