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ISO Cleanroom Classifications

Cleanrooms are used in sensitive medical and manufacturing processes that require contaminants and debris to be below specified levels. The ISO, International Standards Organization, sets forth the specifications on airborne contaminants allowed for each cleanroom classification level. The environment is strictly controlled to maintain appropriate levels of cleanliness and in some cases requires special equipment.

  1. Base level

    • The ISO cleanroom classifications are broken into three main categories beginning with what is considered "Room Air." The area must be below 293,000 5 micron contaminants, 8.32 million 1 micron particles and 35.2 million half micron particles per meter cubed. There is no limit to particles of lower size. These rooms are defined as average work environments with only standard ventilation equipment.

    Classes 1 Through 4

    • ISO classes 3 and 4 allow no particles above 1 micron in size while classes 1 and 2 require no particles larger than two tenths and one half a micron in size, respectively. Additionally, the amount of particles allowed in each is reduced on a magnitude of ten for every reduction in class. For example, class 4 allows 10,000 one tenth of a micron particles per meter cubed while class 3 allows only 1,000. These classes are the upper level of all classified cleanrooms and require specialized equipment to maintain.

    Classes 5 and 6

    • At classes 5 and 6, the ISO standard begins to define the maximum number of particles allowed at sizes of one tenth, two tenths and three tenths a micron in size; these limitations are 1 million, 237 thousand and 102 thousand per meter cubed, respectively. At this level, entrance into the cleanroom requires air baths, clothing and face coverings to prevent the introduction of contaminants into the environment.

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