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
ISO 6 Cleanroom Requirements (Particle Counts)
An ISO 6 cleanroom is required to have roughly 180 air changes per hour of HEPA-filtered air and no more than 293 particles per cubic meter at 5 microns and larger. By comparison, a conditioned office (a non-cleanroom space) holds well over 100 times as many particles per cubic meter. ISO 6 also sets limits for 0.5 micron and 1 micron particles, shown in the table below.
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.
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