Most penetrating particle size MPPS

HEPA and ULPA filters have been developed. In the CEN EN 1822 1998 test method, the filter s efficiency is determined for the most penetrating particle size (MPPS). Depending on the filter s total level of separation and leakage, the filter is classified as HIO, Hll,.. ., H14 and U15, U16, or U17. HEPA filters are commonly used for inlet air in the pharmaceutical, optical, and food industries. 

The particle concentration efficiency tests are used for the various grades of high efficiency air filters (HEPA, ULPA), and use the sub-micrometre aerosols described in earlier paragraphs. The procedures are described in detail in BS EN 1822, which also highlights the Most Penetrating Particle Size (MPPS) as probably the most important performance characteristic. 

Table 6.3 shows the many standards for efficiency testing of HEPA and ULPA filters. New classifications have been defined for both types of filter according to EN 1822 and these are given in Table 6.4. The system is based on letters and figures in the same way as for coarse and fine filters according to the EUROVENT Classes, with H standing for HEPA and U for ULPA. The filters are then divided into eight classes from HIO to U17, depending on their efficiency at the most penetrating particle size (MPPS) and the size of the leaks.

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