Abstract: Non-woven fiber fabrics are described, suitable for use in self-supporting dust filter units having at least one passage (10) defined by wall portions (12) made from air permeable fiber fabric through which wall portions (12) air can pass a d be drawn off along the passage (10) but which prevent the passage therethrough of dust and/or other debris carried by the air. The non-woven fabrics are blends of high temperature resistant fibers. A preferred blend consists of 50% by weight polyimide fibers and 50% by weight aramid fibers, but may include glass fibers, polytetrafuoroethylene fibers, or others and may optionally include an amount of heat activated fibers having a relatively high melting point for example, polyphenylene sulphide fibers.

Abstract: A self-supporting filter unit having at least one passage (10) defined by wall portions (12) made from air-permeable fiber fabric, through which wall portions air can pass and be drawn off along the passage but which prevent the passage therethrough of dust and/or other debris carried by such air, in which the passage is closed off at one end portion and at the other end portion there is formed integral with said wall portions a rigid mounting portion (16) into which the passage (10) opens whereby the filter unit can be supported as part of a filter assembly, wherein the mounting portion (16) includes a first reinforcing portion (18) of material around and secured with said fabric of the wall portion parts of the first reinforcing portion and fabric integral therewith remote from said one end being outwardly flanged, and wherein the mounting portion (16) further includes a second reinforcing portion (20,21) of material positioned over the outwardly flanged portions and secured thereto, said second reinforcing