Abstract: A selective fluid flow control device has a control element which is held in sealing relationship with a housing, with first and second seals being formed to confine the fluid flow through the control element. The first and second seals define a sealed chamber from which the fluid is excluded, and a gas conduit communicates between outside of the housing and the sealed chamber for applying a test pressure to the chamber to test the quality of these seals. In a preferred embodiment, the selective fluid control device is a filter arrangement for a clean room or the like, and the seals are formed against the filter gasket by a seating arrangement formed of an extruded rail that has a web and first and second ribs, the ribs being biased against the gasket.