FALLING FLOW TYPE AIR FILTER STRUCTURE AND AIR STREAM CONTROL AND LEAK TESTING METHOD THEREOF

摘要

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. The filter construction also permits leak testing of the filter by injection of test smoke from the downstream side, through the center board passageway and hollow damper tube, with simultaneous monitoring of the smoke concentration on the upstream side, thereby insuring that the desired level of smoke concentration on the upstream side of the media is reached prior to scanning the downstream side for the presence of particles to detect leaks.