An ISO 6 cleanroom is one of the cleaner classes on the ISO scale, allowing more particles than ISO 5 but far fewer than ISO 7 or ISO 8. The classes are defined by the International Organization for Standardization, a private body made up of 167 national standards organizations. In the United States, the ISO system is used mainly for pharmaceutical, medical device, biotech, and life-science cleanrooms; across Europe and the rest of the world it is used for every industry except semiconductor. For the full scale, see our guide to cleanroom classifications.
Figure 1. ISO-6 optics cleanroom
An ISO 6 cleanroom is classified under ISO 14644-1 based on the concentration of airborne particles. An ISO 6 cleanroom permits a maximum of 35,200 particles ≥0.5 µm per cubic meter of air and 293 particles ≥5.0 µm per cubic meter. ISO 6 is equivalent to the former U.S. FED-STD-209E Class 1,000 classification.
ISO 6 cleanrooms are commonly used for applications such as optics, medical devices, pharmaceutical manufacturing, semiconductor processes, ceramics, lasers, and research and development where tighter particle control is required than ISO 7 or ISO 8.
Particle size
Max particles per m³ (ISO 6)
≥ 0.1 µm
1,000,000
≥ 0.2 µm
237,000
≥ 0.3 µm
102,000
≥ 0.5 µm
35,200
≥ 1 µm
8,320
≥ 5 µm
293
Figure 2 . ISO cleanroom class pyramid – cleanest at top
ISO-6 cleanrooms are required to have 180 air changes per hourof 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 one thousand times as many particles per meter3. ISO-6 cleanroom classification also has requirements for >0.5 micron and >1 micron size particles (see table 1).
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).
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
ISO 6 Gowning and Airlocks
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 7. Climet 150T particle counter
Preguntas frecuentes
Q: Is ISO 6 the same as Class 1,000?
A: They are equivalent. ISO-6 measures particles per cubic meters, Fed Std 209E class 1000 measures particles per cubic foot.
Q: What is the difference between ISO-5 and ISO-6?
A: ISO-5 class cleanrooms have 10X less particles per cubic meter than ISO-6 cleanrooms.
Q: What is the difference between ISO-6 and ISO-7?
A: ISO-7 class cleanrooms have 10X more particles per cubic meter than ISO-6 cleanrooms.
Q: Is an ISO-6 cleanroom sterile?
A: ISO-6 is a measurement of how many particles per cubic meter. It does not specify whether the cleanroom is sterile (number of viable or live particles such as mold, virus, bacteria or microbes).
Q: What air changes per hour does an ISO 6 cleanroom require?
A: ISO-6 cleanrooms are typically designed to 180 air changes per hour.
Q: How is an ISO 6 cleanroom tested?
A: Typically ISO-6 cleanrooms are tested doing at rest and operational particle counts. Other tests used when commissioning an ISO-6 cleanroom include air pressure compared to ambient, temperature control, humidity control and HEPA air changes per hour. Once operational ISO-6 pharmaceutial and medical devices cleanrooms following CGMP do viable testing (settling plates and surface sampling for microbes).
Q: Does ISO 14644-1 specify HEPA filters?
A: The ISO standard does not specify what type of filtration only allowable airborne particle counts per cubic meters. ISO-6 cleanrooms are typically built with either HEPA filters or ULPA filters. Learn more https://www.americancleanrooms.com/hepa-vs-ulpa-filters/
The author Anthony Chien has worked at American Cleanroom Systems for past 14 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-4 thru ISO-8 (class 100 to class 100k) modular cleanrooms for pharmaceutical cleanrooms, medical device cleanrooms, and industrial cleanrooms.
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