Classification and testing of air filters

The air filter refers to the apparatus for removing the particulate matter in the air by filtration, adhesion or tip trap, such that the concentration of particulate matter in the air is lowered, and the purpose of purifying air is achieved.

At present, there are two filter standards in my country, respectively:

GB / T 13554-2008 High efficiency air filter

GB / T 14295-2019 Air filter

According to national standard air filters, it is divided into initial, context, high-altitude, sub-efficient, efficient (HEPA) and ultra-efficient (ULPA) filters.

According to the test method of GB / T 13554, the high-efficiency air filter used by the high-efficiency air filter is 0.5 μm, while the high-efficiency air filter defined in GB 50073-2013 \"Clean Factory Design Specification\" is 0.3 μM, here there is a little in stock.

According to the standard of Europe and the United States, the count particles of the high-efficiency filter are 0.3μm. I don't know why China's test method chooses 0.5 μm, and the recognized most easily penetrating particles are 0.3 μm, so the high-efficiency filter test of the Naglan Flame method. 99.9% Filtering efficiency may have to be a discount, as for the same definition method of national standards, it can only be explained.

Two filter test method

Courage

The filter is mounted in a standard test wind hole, and the upper wind is continuously dust (generally loened dust). Every time, measure the dust quality of the filter through the filter, thereby obtaining the filtering efficiency calculated by the filter in this stage. The test dust particle size range is ≥5 μm.

Colorimetric method

Sampling before and after the filter, the dust is filtered through the filter paper, and the contaminated filter paper is irradiated under the light source, and then the light transmittance of the filter paper before and after the filter is measured by the phototube colorimeter (photodemeter); in the ingredients of dust, Under the same conditions, the same relationship is proportional to the amount of optical density and dust removal, which is calculated to calculate the filter efficiency, which is mainly treated with dust from the particle size ≥ 1 μm particles.

Counting method

The full-term particle counter method, the gas-soluble gas stream is transmitted through the aerosol generator, and the gas absorber on the upper and downstream of the test device is collected, and the count concentration value is measured by a coagulating nuclear particle counter (CNC) or an optical particle counter (OPC), then The counting filtering efficiency of the filter material is obtained. The aerosol concentration of different particle sizes range can be measured.

Oil fog method

Generally, DOP (phthal octyl phthal octyl phthal), a multi-dispersion phase liquid aerosol is emitted by the device, and the mass average diameter of the particles is (0.28 ~ 0.34 μm), and the mass optics downstream of the filter is detected by the oil mist. The concentration and then obtain the mass efficiency of the filter element. This method is mainly for particulate matter having a particle size of ≥ 0.3 μm.

Sodium flame method

NaCl aerosols were emitted by generators, and the mass concentration of the filter element was detected by the Na Fire Meter and then the mass efficiency of the filter element was obtained. For the filter material test, the mass medium having a test aerosol particles is about 0.4 μm, and the median diameter is (0.09 ± 0.02) μm, and the number geometric standard deviation is less than or equal to 1.86; for the filter test, test aerosol occurs The mass diameter of the particles is 0.5 μm.