Abstract: A HEPA-type, downflow air filter module is disclosed, having a damper supported upon a hollow tube for adjustable movement relative to an opening through which air enters the enclosed chamber or plenum above the filter media. The hollow damper support tube is axially aligned with a passageway between upstream and downstream sides of the center board which conventionally separates the media core into two halves in such filter modules. The passageway is normally sealed by a plug which may be removed from the downstream side of the module for measuring and adjusting air flow into the module, as controlled by the position of the damper which may be adjusted while air flow is being measured.

Abstract: A HEPA-type, downflow air filter module is disclosed, having a damper supported upon a hollow tube for adjustable movement relative to an opening through which air enters the enclosed chamber or plenum above the filter media. The hollow damper support tube is axially aligned with a passageway between upstream and downstream sides of the center board which conventionally separates the media core into two halves in such filter modules. The passageway is normally sealed by a plug which may be removed from the downstream side of the module for measuring and adjusting air flow into the module, as controlled by the position of the damper which may be adjusted while air flow is being measured.

Abstract: Apparatus for sensing the total pressure of a fluid flowing through a duct by a plurality of open-ended impact tubes fixedly arranged in a transverse plane of the duct and connected to a common manifold tube. Flow straightening means upstream of each sensing tube are provided by individual straightener tubes, open at both ends and arranged axially in the direction of fluid flow, in association with each sensing tube. The straightener tubes extend upstream from the ends of the impact tubes by a distance equal to at least eight times the transverse dimension of the straightener tube. In the preferred embodiment, separately manifolded static pressure sensing tubes are also provided, and serve as support means for the straightener tubes.

Abstract: Apparatus for permanent installation in a heating or air conditioning duct to sense total and static pressure of air flowing therethrough. A plurality of manifolds are arranged within the duct to sense total pressure at a number of selected locations in a transverse plane of the duct. The plurality of manifolds communicates with a connecting manifold either directly or through sensing tubes arranged axially within the manifold tubes. Static pressure is also sensed at a plurality of preselected locations in the duct and communicated to at least one additional manifold tube arranged within the duct. Total and static pressure are communicated through single openings in the duct well for attachment exteriorly thereof to an appropriate measuring instrument.