ISO Cleanroom Classifications

by | Nov 3, 2016

ISO cleanroom standards

ISO cleanroom standards

Originally the U.S. General Service Administrations’s standards known as FS209E were used as the global standard. Since then, global classifications and standards have been created and adopted. The ISO cleanroom standards offer international consistency and have been developed by a technical committee of controlled environment subject matter experts.

FS209E contains six classes, while the ISO 14644-1 classification system adds two cleaner standards and one dirtier standard (see chart below). The “cleanest” cleanroom in FS209E is referred to as Class 1; the “dirtiest” cleanroom is a class 100,000. ISO cleanroom classifications are rated according to how much particulate of specific sizes exist per cubic meter (see second chart). The “cleanest” cleanroom is a class 1 and the “dirtiest” a class 9. ISO class 3 is approximately equal to FS209E class 1, while ISO class 8 approximately equals FS209E class 100,000.

Controlling contamination is essential in many manufacturing and research activities. The use of clean rooms, along with strict and stringent processes, makes this possible. The recently revised ISO standards for cleanrooms can help.

In November 2001, Federal Standard 209E was superseded by the new ISO 14644-1 international standards. References to FS209E are still used; the comparison chart below illustrates the relationship between the two standards.

ISO 14644-1 FEDERAL STANDARD 209E
ISO Class English Metric
ISO 1
ISO 2
ISO 3 1 M1.5
ISO 4 10 M2.5
ISO 5 100 M3.5
ISO 6 1,000 M4.5
ISO 7 10,000 M5.5
ISO 8 100,000 M6.5
ISO 9

Airborne Particulate Cleanliness Classes (by cubic meter):

CLASS Number of Particles per Cubic Meter by Micrometer Size
0.1 micron 0.2 micron 0.3 micron 0.5 micron 1 micron 5 microns
ISO1 10 2
ISO2 100 24 10 4
ISO3 1,000 237 102 35 8
ISO4 10,000 2,370 1,020 352 83
ISO5 100,000 23,700 10,200 3,520 832 29
ISO6 1,000,000 237,000 102,000 35,200 8,320 293
ISO7 352,000 83,200 2,930
ISO8 3,520,000 832,000 29,300
ISO9 35,200,000 8,320,000 293,000

Table 2: Selected airborne particulate cleanliness classes for cleanrooms and clean zones. Classification Parameters from ISO 14644-1.

ISO 14644-1 Cleanroom Standards
In 1999 Cleanrooms and associated controlled environments-Part 1: Certification of Air Cleanliness was created to replace the old Federal Standard 209-E.  Within this document the various classification systems are based upon the requirements for counts associated with non-viable particulates. The limits stated in this document are depicted in Table 1.

Learn more about cleanroom-related ISO standards:

ISO 14644-1:2015
Cleanrooms and associated controlled environments — Part 1: Classification of air cleanliness by particle concentration

ISO 14644-2:2015
Cleanrooms and associated controlled environments — Part 2: Monitoring to provide evidence of cleanroom performance related to air cleanliness by particle concentration

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