Cleanrooms and equipment

Which is the common definition of HEPA filter performance?

  1. ACapturing at least 99.97% of particles 0.3 µm in size
  2. BCapturing at least 50% of particles 10 µm in size
  3. CRemoving at least 99.99% of gaseous molecules
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Answer: A. Capturing at least 99.97% of particles 0.3 µm in size

A HEPA filter is defined as having a collection efficiency of at least 99.97% for particles of about 0.3 µm, close to the size that is hardest to filter (as in JIS and other standards). The higher-performance ULPA filter is specified at 99.9995% or more for 0.15 µm particles. Neither can remove gaseous molecules.

  • A. Correct. 99.97% or more at 0.3 µm is the benchmark.
  • B. That is the performance of a very coarse filter.
  • C. HEPA filters capture particles and cannot remove gases.
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