What is the efficiency of an air filter? The ratio of the amount of dust collected by the filter to the amount of dust in the unfiltered air is the " filtration efficiency " .
Different operating environments require different levels of cleanliness, so filters with different efficiencies and equivalent fresh air volumes are required to meet different levels of cleanliness.
Among the factors that determine the filtration efficiency, the meaning of dust " amount " is various, and the filter efficiency value calculated and measured from it is also different. In practice, there are the total weight of dust and the number of dust particles; sometimes it is for the amount of dust of a certain typical particle size, sometimes it is the amount of all dust; Fluorescence amount (fluorescence method); there is an instantaneous amount of a certain state, and there is also a weighted average amount of change efficiency value of the whole process of dust emission. Therefore , if the same filter is tested by different methods, the measured efficiency value will be different . Without the test method, the filtration efficiency cannot be discussed.
Therefore, different methods should be used to detect different air filters . When selecting a filter, you should not only consider the efficiency of the air filter, but also understand its test method and test dust.
China first adopted the atmospheric dust group counting method to test the efficiency of the filter in the world, and promulgated GB12218-1990 "Test Method of Filter Performance for General Ventilation" in 1990 .
For high efficiency air filters, test methods and test dust greatly different countries, such as issued in China GB / T6165-1985 "Test Method performance HEPA filter, the transmittance and resistance" method and the oil mist as sodium flame method Statutory performance test method; the United Kingdom uses the sodium flame method ( BS3928-1969 ;) DOP (dioctyl phthalate) method proposed by the United States. Various countries have proposed air filter standards based on the test method standards, such as the BS5295 standard with DOP as the test dust in the United Kingdom, EVROVENT4 / 9 formulated by the European Air Treatment Equipment Manufacturers Association, various air filter standards and efficiency at home and abroad See Table 3-3 for comparison.
The test methods of air filters commonly used at home and abroad are :
(1) Weight method
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