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The development history of high-efficiency air filter test method


With the continuous development of science and technology, the production of modern industrial products and modern scientific experimental activities require increasingly higher indoor air cleanliness, especially microelectronics, medical, chemical, biological, food processing and other industries require miniaturization , Precision, high purity, high quality and high reliability indoor environment, the main way to achieve this goal is to widely use air filters in clean air conditioning systems. Among them, high efficiency (HEPA) and ultra high efficiency (ULPA) filters are the last protection for dust particles to enter the clean room. Its performance is directly related to the clean room level, which in turn affects the process and product quality.
To this end, many countries have formulated and promulgated relevant standards for performance test methods: The US Military Commission formulated the military standard MIL-STD-282 in 1956, using the DOP (dioctyl phthalate) method, which uses forward light scattering The photometric meter detects the turbidity ratio of the gas sample before and after the filter to calculate the filtering efficiency of the filter. This standard has not been changed significantly and has been used so far; the BS3928 standard established by the United Kingdom in 1965 uses the sodium flame method. The detection instrument is flame photometry This method was adopted in the European OV4ENT4/4 standard of 1973; China issued GB6166-85 "Effective Air Filter Performance Test Method" in 1985, which used the oil mist method and the sodium flame method as the legal performance test method; Japanese Industrial Standard JISB 1 Performance Test Method of High Efficiency Filter 1.1 The efficiency test of high efficiency filter is known from the foregoing.
The efficiency detection methods of high-efficiency filters are various, but after more than half a century of development and evolution, the current impact is greater and the scope of use is wide: DOP method, particle counting method and the most penetrating particle size t (MPPS )law.
   1 The DOP method refers to the thermal generation (condensation method) DOP aerosol plus photometer measurement method. This method was first proposed by the United States: heating DOP liquid into vapor, the vapor is condensed into tiny droplets under certain conditions, and the monodisperse aerosol particles of about 0.3"m are left after removing the oversized and undersized droplets. After the DOP enters the air duct, a light-scattering photometer is used to detect the turbidity ratio of the gas sample before and after the filter to calculate the filter efficiency.
   2 Particle counting method The particle counting method uses a particle counter as the detection instrument, and the dust source uses monodisperse or polydisperse aerosol. Polydisperse aerosols are produced by spraying method (cold generation). DOP particles are sometimes used in colloidal sources, compared with thermally generated DOP particles. Their materials are the same, but the degree of dispersion and detection methods are not the same 9927: 1999 "clean The air filter performance test method for indoor use adopts the particle counting method to test the high-efficiency filter; Europe established the BSEN-1822 standard in 1998-2000, and uses the most permeable particle size (MPPS) method to detect the filter filter effectiveness. The following will analyze and compare multiple standards at home and abroad from the aspects of efficiency testing, leak detection and aerosol sources, and focus on the problems existing in the process of high-efficiency filter performance testing, and point out the direction of future research and development in this field.