Research On Particle Counting Efficiency Test Problems Of HEPA Filter & Media

With the development of modern technology, there is higher demand for control over aerosol particles both in size and number. Development of high-powered air-filtration materials and filters is required in clean air industry. Researches on filter testing methods are necessary to guarantee the renovation of filter industry. Without any revision over the past decades of years, the national standards for high efficiency filter paper testing currently used in China can not adaptive to the development of high efficiency paper industry. Though European standard for filter testing EN1822 becomes prevalent recent years, it is still immature and many problems need to be solved in practice in China.Error analysis on the experiment data from MPPS(most penetrating particulate size)filter efficiency testing equipments demonstrates that the difference between testing result derived from one laser particle counter and that from two laser particle counters is acceptable if the testing equipment is reasonably designed. This paper also discusses the influence of the dilution part configuration on the testing result. The testing result derived with varied aerosol concentration has been proven inaccurate. The time period required for particle release equipment to be stable at the beginning of the testing is longer than that required in the testing process. The result accuracy is positively correlated with this time period. How to determine this time period has been discussed in this paper by experiment data analysis. One level lower filter paper is commonly chosen when producing filter with certain level efficiency. Such deviation is due to testing method difference of paper testing and filter testing. When these two matters are tested with the same method, filter manufacture should choose filter paper of the same efficiency level with the filters to be produced. Leak point detection method is also discussed in this paper. It indicates the varied air volume method can only work well for filters with large leak points, while it work poorly to detect leak points in small size.The failure of the popularization of MPPS filter efficiency testing method barriers the course for the filter paper produced in China being recognized by the same industry abroad. To improve researches on problems about MPPS testing method to enhance its application on filter, filter material testing is the exact precondition that homemade air filter products being recognized in the international market.