Cleanrooms and equipment

Which statement about ISO 14644-1 cleanliness classes is correct?

  1. AThe larger the number, the cleaner
  2. BThey are defined by particle weight rather than particle count
  3. CEach step down in the class number N cuts the allowed particle count by about a factor of 10
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Answer: C. Each step down in the class number N cuts the allowed particle count by about a factor of 10

In ISO 14644-1, ISO Class N limits particles of 0.1 µm and larger to 10 to the power N per cubic meter (limits for other sizes follow from a formula). For example, Class 5 allows 100,000 and Class 4 allows 10,000, so the smaller the number, the cleaner the room.

  • A. The smaller the number, the cleaner.
  • B. They are defined by particle number concentration.
  • C. Correct. The particle limit changes tenfold per class.
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More Cleanrooms and equipment questions

  1. Which type of cleanroom blows clean air from parts of the ceiling and maintains cleanliness by mixing with and diluting the room air? Its cleanliness is lower than with unidirectional flow, but its equipment cost is lower.
  2. Which filter is used to remove airborne molecular contamination (AMC) such as ammonia and organics from cleanroom air?
  3. In cleanroom air conditioning, which unit filters outside air and adjusts its temperature and humidity before supplying it to the recirculating room air?
  4. In a fab's automated material handling system, which automated storage holds FOUPs temporarily until their next process step?
  5. In automated transport in a bay-type fab, which pair correctly names transport between bays and transport linking tools within a bay?