Study On The Particle Count Efficiency At The Most Penetrating Particle Size For High Efficiency Fibrous Filter Media

The high efficiency particulate air (HEPA) filters are widely used in the indoor particle contaminant removal and high class level cleanroom. With the development of modern science and technology, it is necessary to develop the high performance HEPA filter media and units. The development of method of testing HEPA filter media performance is the guarantee of the high quality fibrous filter media. Because the state-of-art filtration theories and test instruments occur, the minimum efficiency at most penetrating particle size (MPPS) is used to mark the performance of HEPA filter media. The current Chinese standard of filter media performance test isn't suitable for the development of HEPA filter media industry. Therefore, it is required to study the efficiency of MPPS for filter fibrous media and the related test method.According to the analysis of filtration mechanisms for fibrous media and the experimental comparison, the most matched theoretical equation was found to calculate the MPPS efficiency of HEPA filter fibrous media made by the domestic factory. Through theory analysis, this study considered the influential factors on the media performance and the applicable test method to get the particle size efficiency. Referred to the advanced test standards and theory analysis results, the MPPS count efficiency test system was designed and built. The test system mainly includes whole measurement system, aerosol generator, particle count system, the integration of automatic control system and developed aerosol sample dilutor.The MPPS test system is further optimized by the analysis of measurement error and the influential factors. The amount of experimental data and comparison test result from the most advanced MPPS test system prove the stability, applicability and repeatability of the built test system.The influence of relation of filtration velocity on the penetration and MPPS was studied by the theoretical analysis and experiments, and it concludes a semi- empirism equation. At the same time, the experiments and theory calculation of HEPA media leak indicate the effect of the leak size and infiltration velocity on the HEPA filter media efficiency. The suggestion on the leak test method is provided.The numerous experimental data and deep theoretical analysis prove it is applicable to use the test method of MPPS count efficiency in China, and the suggestion on the modification of MPPS method is provided. The study accumulates a lot of experimental data and theoretical research experiences for introducing MPPS test method into the China filter media industry. It will promote the development of air cleaning industries.