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What is an ISO-6 Cleanroom Classification?

agosto 16, 2023

ISO-6 cleanroom classification is one of the highest levels of the cleanroom classes. The ISO cleanroom standards are set by the International Organization for Standardization ( They are a private international organization with a membership of 167 national standards bodies. The ISO cleanroom classification system used in United States primarily for pharmaceutical cleanrooms, medical device cleanrooms, biotech cleanrooms, and life-science cleanrooms. The Europe and the rest of world uses the ISO cleanroom classification system for all industries except semiconductor.

Figure 1. ISO-6 optics cleanroom

ISO-6 cleanrooms are required to have 180 air changes per hour of HEPA filtered air and less than 293 particles/meter3 greater or equal to 5 microns

By comparison, a conditioned office space (non -cleanroom space) would have more than 100X as many particles per meter3. ISO-6 cleanroom classification also has requirements for >0.5 micron and >1 micron size particles (see table 1).

Table 1. ISO Cleanroom Classifications

There is a separate FED 209E cleanroom classification system that has been historically used in United States for industrial cleanrooms such as semiconductor cleanrooms and printed circuit board cleanrooms. The ISO cleanroom classification is on metric system (particles per meter3). The FED 209E cleanroom classification system is based on imperial system (particles per feet3). There are comparable ISO and FED 209E cleanroom classes for each level of cleanliness.  An ISO-6 cleanroom classification corresponds to FED 209E class 1000 cleanroom classification (see table 2).

Table 2: FED STD 209E Cleanroom Classifications

Common applications for ISO-6 cleanroom classification rooms

  • Semiconductor manufacturing cleanroom
  • Optics manufacturing cleanroom
  • Ceramics manufacturing cleanroom
  • Laser test cleanroom
  • Pharmaceutical manufacturing cleanroom
  • R&D cleanroom
Figure 2. ISO-6 Ceramics manufacturing cleanroom
Figure 3. ISO-6 laser cleanroom
recirculating modular cleanroom
Figure 4. Air Flow simulation for ISO-6 recirculating modular cleanroom

ISO-6 air flow is typically recirculating. In recirculating cleanrooms, the air is exhausted thru low return air grills back to the plenum where the HEPA or ULPA fan filter units reclean the air and draw it back into the cleanroom. As a result, the air in the cleanroom is cleaned over and over again (180x per hour), resulting in the cleanest environment possible.

Filtration for ISO-6 classification cleanrooms is done with HEPA or ULPA filters. The best modular cleanroom design uses a negative pressure plenum with HEPA or ULPA fan filter units in the ceiling and incorporated low wall air returns to achieve laminar air flow. The HEPA or ULPA filtered air sweeps dirt down to the floor and horizontally to the low wall air returns. ULPA filters are commonly used in ISO-6 cleanrooms because ULPA filters screen particles down to 0.12 micron size whereas HEPA filters only screen particles down to 0.3 micron size.

Cleanroom gowning for ISO-6 classification cleanrooms. Typically, cleanroom personnel wear cleanroom knee high shoe covers to avoid tracking dirt into the cleanroom and full cleanroom bunny suits.  All the garments are manufactured from special non particulating cleanroom approved materials. Options include disposable or washable (you send back to cleanroom laundry) garments. It is critical the personnel wear cleanroom garments if user wants to maintain ISO-6cleanroom classification.

Figure 5. Cleanroom garments for ISO-6 cleanrooms

Why gown room/airlock for ISO-6 classification cleanroom. Because an ISO-6 classification cleanroom only allows 7 particles/ft3 > 5 microns  if a door is even briefly opened to the dirty exterior it will let thousands of particles. The gown room/airlock prevent the particles from entering the ISO-6 cleanroom. The gown room will have HEPA filtration to reduce the number of particles the ISO-6 room will be exposed to. Gown room / airlocks are a critical part of your ISO-6 classification cleanroom.

Particle testing for ISO-6 cleanrooms. Particle testing must be done with bench top laser particle counters which measure a minimum of 1 ft3 per sample location. The larger sample size is due to the extremely small number of particles per cubic foot that are found in ISO-6 cleanrooms.

Figure 6. Climet 150T particle counter

Property American Cleanroom Systems 2023

The author Anthony Chien has worked at American Cleanroom Systems for past 10 years. He has more than 40 years of cleanroom experience. Anthony has a BS and MS in Electrical Engineering specializing in semiconductor manufacturing from the University of Illinois. American Cleanroom Systems is a design build modular cleanroom manufacturer based in Rancho Santa Margarita CA. It is expert in ISO-5 thru ISO-8 (class 100 to class 100k) modular cleanrooms for pharmaceutical cleanrooms, medical device cleanrooms, and industrial cleanrooms.

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