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The EN1822 standard Simplified

Filter class of Absolute filters

Absolute filters include all filters with filter classes E10 through U16. These filters are also named based on the filter class. Thus, we speak of:

  • EPA (Efficiency Particulate Airfilter) filters,
  • HEPA (High-Efficiency Particulate Airfilter) filters or
  • ULPA (Ultra Low Penetration Airfilter) filters.

EN1822:2019 standard

The standard that indicates which filter class applies is called the EN1822 standard. This standard has several revisions / updates since its first version in the 1990s. Hence, the year is stated behind the name of the standard. At the moment, we are talking about the EN1822:2019 standard. In this version, the international test procedure ISO 29463 is added as well.

Wherever the absolute filter is used, it will always be certified according to these two standards. Whether the filter is placed in a controlled environment such as a clean room, in an air handling system, or a separate air cleaner.

How do filters get tested according to EN1822:2019?

An absolute filter is classified according to its effectiveness in removing aerosols from the air stream. The EN1822:2019 standard assures that a filter meets the specified removal efficiency.

During factory tests of the filter, they do not measure how many particles are captured, but by using a test aerosol, they measure the levels of suspended particles in the air passing by the filter.

For this, the MPPS (most penetrating particle size) of the filter will be determined first. That is an abbreviation to indicate the size of the dust particles that penetrate the filter the most. This MPPS varies approximately between 0.1 and 0.2 microns. That is actually the least strong point, in terms of the particle size of the filter in question.

Based on different air flows, a percentage is used to express the efficiency on these particles. This table gives an overview of the different classifications. For example, an H14 filter class means that the HEPA filter is 99.995% effective against the MPPS. The slightly larger particles are blocked even more efficiently. If, measured with a different particle size (larger), the percentage would increase.

Depending on the final filter class, an individual leak test will follow for each filter. Except for the EPA filters, since it showed that this is not useful in practice.

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