Abstract: An adjustable damper or air flow control valve for clean room systems, laminar flow benches, filter diffusers, fan/filter units and the like includes a fixed plate defining a plurality of rows of apertures. The plate is fabricated from an aluminum-clad fiberboard. A movable, foam plate is positioned on the fixed plate. The foam plate is fabricated from a cross linked polyethylene foam and also defines a plurality of apertures. The foam conforms to the fiberboard plate and prevents cross flow between adjacent apertures. Relative movement between the two plates moves the apertures into and out of alignment to control the flow of air to a filter.

Abstract: An air filtering system of the type used in clean rooms and the like supportable from a ceiling. The unit includes a supporting frame with an opening therethrough, the supporting frame being suspended from the ceiling by cables or the like. A filter having a filter frame therearound is placed within and across the opening in the support frame. A cutting wire is positioned between the supporting frame and the filter frame around the periphery of the opening. One end of the wire is free and extends below the two frames. The other end is fixedly secured to either the filter or support frame. A cuttable seal is applied between the filter and support frames around the periphery of the opening. Clips are also provided to hold the filter within the opening. When one wishes to remove the filter, the free end of the cutting wire is pulled, cutting the seal around the periphery of the opening, thereby allowing the filter and filter frame to be removed from the support frame opening.