This edition is the result of a systematic review and includes changes in response to user and expert feedback
validated by international enquiry. The title has been revised to “Classification of air cleanliness by particle
concentration” to be consistent with other parts of the standard. The nine ISO cleanliness classes are retained
unchanged, but Table 1 defines the particle concentration at various particle sizes for the nine integer classes.
The use of Table 1 ensures better definition of the appropriate particle-size ranges for the different classes. A
formula is retained to allow definition of intermediate decimal classes. The standard retains the concept of
ultrafine and macroparticle descriptors for particle sizes outside the range appropriate for measurement using
airborne particle counters.
The most significant change is the adoption of a more consistent statistical approach to the selection of
number of sample locations and the evaluation of the data collected. The number of sample locations
compared with the 1999 version of the standard have been changed. The approach allows each location to be
treated independently with a 95 % level of confidence that at least 90 % of the cleanroom or clean zone will
comply with the maximum particle concentration limit for the target class of air cleanliness. A reference table is
provided to define the number of sample locations required. Because a degree of randomness is required, the
cleanroom or clean zone is then divided into equal sectors and the sample location placed randomly within
each sector.
Finally, the annexes have been reordered to improve the logic of the standard.
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 14644-1 was prepared by Technical Committee ISO/TC 209, Cleanrooms and associated controlled
environments.
This second edition cancels and replaces in whole the first edition (ISO 14644-1:1999), which has been
technically revised.
ISO 14644 consists of the following parts, under the general title Cleanrooms and associated controlled
environments:
Part 1: Classification of air cleanliness by particle concentration
Part 2: Specifications for monitoring and periodic testing to prove continued compliance with ISO
14644-1:XXXX
Part 3: Test methods
Part 4: Design, construction and start-up
Part 5: Operations
Part 6: Vocabulary
Part 7: Separative devices (clean air hoods, gloveboxes, isolators, and mini-environments)
Part 8: Classification of airborne molecular contamination
Part 9: Classification of surface cleanliness by particle concentration
Attention is also drawn to ISO 14698, Cleanrooms and associated controlled environments —
Biocontamination control:
Part 1: General principles and methods
Part 2: Evaluation and interpretation of biocontamination data