Filter classification The filter classes and their IDs are based on international testing methods and standards. Their classifications divide filters into 17 distinct classes. The class ID consists of the letter ‘G’ (coarse mesh filter), ‘F’ (fine filter), ‘H’ (HEPA filter), or ‘U’ (ULPA filter) and a number from 1 through 17, where ‘1’ corresponds to the most modest coarse mesh and ‘17’ to the highest-grade ULPA filtering class. Filter classes
The EN 779 standard determines what is called the collecting efficiency by weight for coarse mesh filters and the particle collecting efficiency for fine filters. The sub-standards of the EN 1822 standard contain specific test methods for HEPA and ULPA filters.
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