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The particle capture mechanisms in aerosol filtration result in a most penetrating particle size for process gases used by the micro-electronics industry. The most penetrating particle size for fibrous filter media and microporous membrane filter media have been measured to be typically 0.15μm and 0.05μm, respectively. Filter performance ratings should be based on the retention of particles at the most penetrating particle size. The retention ratings for HEPA fiberglass filters have been determined to be ≥99.99% and for typical membrane filters ≥99.9999999%.
The shedding of particles from the downstream side of various types of Point-of-Use filter devices was evaluated, using laser and condensation nucleus type particle counters. All types of filter devices performed similarly during steady flow operation but performance differences were observed when either pulsed flow or mechanical vibrations occurred. In general, the membrane filter devices shed less particles than the fiberglass filter devices, and the membrane filter devices that used stacked disc molded supports were cleaner than the pleated filter devices.
fibrous filter, membrane filter, aerosol filtration, filtration mechanisms, particulate shedding, particulate penetration
Accomazzo, Mauro A.
Director of Applications Engineering, Research and Development Department of Millipore Corporation, Bedford, MA
Grant, Donald C.
Manager of the Particle Technology Laboratory, Research and Development Department of Millipore Corporation, Bedford, MA