Clean Room Classifications


In 1987 the FDA began to set clean room guidelines with the definitions of two kinds of clean rooms, as judged by the microbiological content in the air: “critical” areas (class 100) were to only use sterilized products or items, and “controlled” areas (class 100000) were to only handle unsterilized products or items, sterilized or held for later use. However, in 2004, the FDA released “Sterile Drug Products Produced by Aseptic Processes – Current Good Manufacturing Practice,” which is now the standard set of guidelines for clean room classifications. The FDA guidelines do not lay down a specific purpose for anything but the class 100 areas because different facilities require different levels of sterilization and different rooms for the handling of their products.

Class 100

  • Class 100 areas or “Critical Areas” have an ISO (International Organization for Standardization) designation of 5. This classification is a measurement of the number of particles of a certain size which are found per foot of space. Microbiological samples taken in class 100 areas should not yield contaminants. This is the highest level of clean room and it suitable for the handling of sterilized products and items. In such areas sterile containers can be filled and closed with a minimal risk of contamination. Critical areas are used for any product which cannot be “terminally sterilized” once it is assembled, due to adverse effects to the product, such as with some medicines.

Class 1000

  • Class 1000 areas have an ISO designation of 6. These areas are supporting clean areas defined by their function. Class 1000 clean areas typically pose as facilities for sterilizing products and items before they enter the critical areas. This is so any microbiological contaminants are filtered away before objects such as packaging, bottles or closures are brought into the more sterile clean room areas.

Class 10,000

  • Class 10,000 supporting clean areas have an ISO designation of 7. The FDA recommends that rooms adjacent to critical areas have no less than this classification, so that contaminants aren’t transferred in. Air should flow from the highest class areas, or critical areas, into these supporting clean areas and workers are required to wear different levels of sterilized garments in differently classed areas. Clean room support areas often include things like changing facilities, where the level of sterilization is lower than that of the critical area and grows progressively higher as the worker moves from one area to the next. This allows contaminants to be filtered out and to be kept outside the critical areas.

Class 100,000

  • Class 100,000 clean rooms have an ISO designation of 8. This is the lowest classification given in the FDA’s guidelines and is the least controlled of the clean rooms. Are may be for changing facilities, as storage areas for unsterilized equipment, items or products, or to assemble products for later transfer to higher level clean rooms.

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