Abstract: A stackable filter device for filtering an input to a source of suction comprises: a substantially hollow filter pad having first and second filter walls constructed of a filter material, the periphery of the first filter wall being sealingly engaged to the periphery of the second filter wall to form the filter pad, each of the filter walls having an aperture. The first and second filter walls each have an annular member fixedly contacted to the circumferential edge of the aperture. The annular members support the aperture, and are structured so as to integrally form connectors operable to removably connect the filter device to the source of suction or to an additional filter device on a first side of the filter device and to a sealing end cap or an additional filter device on a second side of the filter device. The filter device preferably includes a tubular stiffening member passing through the filter device. The stiffening member is rigidly attached at each end thereof to one of the annular members.