HEPA AND ULPA FILTERS OFFER A COMBINATION OF HIGH EFFICIENCY, LOW PRESSURE DROP AND SATISFACTORY LOADING CHARACTERISTICS FOR CLEAN ROOM USE.

HEPA and ULPA filters offer a combination of high efficiency, low pressure drop and satisfactory loading characteristics for clean room use. HEPA and ULPA filters are composed of a collection of randomly oriented fibers of varying diameters and lengths, which are packed, compressed or otherwise held together as mats, often with the aid of acrylic binders. This 'paper' is usually 10-20 mils thick and is pleated with separators between the folds so that a large filtering area can be placed into a relatively small module. The filter assembly is bonded into a wood, aluminum or steel frame to prevent leaks. To ensure laminar flow throughout the clean room, such filters typically make up most or all of the ceiling, with the vents for sidewall return air at floor level or, if raised floors are used, below floor level. The return air typically makes up around 80-90% of the air filtered, with the remainder consisting of prefiltered outside air. 6 refs.