This article is the first of a two-part series. The second article titled "Investigations of Particle Penetration in Fibrous Filters, Part II. Theoretical" will appear in the upcoming March/April 1998 issue of the Journal of the IEST.

The performance of high-efficiency filters is evaluated using a semiautomated test system. This system is used for accurate measurements of submicron particle penetrations and pressure drops of filters. The system is designed to minimize errors and uncertainties associated with filter testing procedures. New commercial filter media, rated from ASHRAE-grade to ULPA, are tested using this system. The particle penetration characteristics of these media are obtained at different face velocities, ranging from 2 to 20 cm/s (0.79 to 7.9 in/s), and the particle diameter is varied from 0.05 to 0.05μm. The efficiencies of these media range from 15 percent to 99.9999 percent. The particle penetration characteristics of the media are consistent with the theories of collection by diffusion and interception in the range of operating conditions studies. The presence of the most penetrating particle size is observed, varying from 0.1 to 0.3μm for the different media. The most penetrating particle size is shown to shift toward the smaller particle size for increasing face velocity.

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