Cleanrooms and equipment

Which ISO 14644-1 cleanliness class corresponds to Class 100 of the former US federal standard (no more than 100 particles of 0.5 µm or larger per cubic foot)?

  1. AISO Class 5
  2. BISO Class 1
  3. CISO Class 9
Show answer and explanation

Answer: A. ISO Class 5

Class 100 of the former US federal standard roughly corresponds to ISO 14644-1 Class 5. ISO classes are defined by particles per m³, and each step down in class number allows one-tenth as many particles. Expressions such as 'Class 100' are still sometimes used as legacy terms.

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