ISO/TR 14644-21:2023

TECHNICAL ISO/TR
REPORT 14644-21
First edition
2023-08
Cleanrooms and associated controlled
environments —
Part 21:
Airborne particle sampling techniques
Salles propres et environnements maîtrisés apparentés —
Partie 21: Techniques de prélèvement des particules en suspension
dans l’air
Reference number
© ISO 2023
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Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative documents . 1
3 Terms and definitions . 1
4 Determination of airborne particle concentration . 2
4.1 General . 2
4.2 Classification . 3
4.3 Monitoring . 4
4.4 Other LSAPC applications . 4
5 Sampling airborne particles – things to consider . 5
5.1 General . 5
5.2 Instrument selection . 5
5.2.1 General . 5
5.2.2 Considered particle size selection . 6
5.2.3 Required sample volume and sample flow rate . 7
5.3 State of occupancy . 7
5.3.1 General . 7
5.4 Sample locations – points to consider. 7
5.4.1 General . 7
5.4.2 Sampling locations for classification . 7
5.4.3 Sample locations for monitoring . 9
5.5 Instrument measurement issues. 10
5.5.1 General . 10
5.5.2 Sampling errors . 10
5.5.3 Sample measurement errors . 13
5.5.4 Sample tubing issues . 14
5.6 Decision tree . 16
5.7 Examples of use of the decision tree . 19
5.7.1 General . 19
5.7.2 Example 1 . 19
5.7.3 Example 2 . 21
5.7.4 Example 3 . 23
6 Verifying a system .25
Bibliography .26
iii
Foreword
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
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ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO document should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use
of (a) patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed
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www.iso.org/iso/foreword.html.
This document was prepared by ISO/TC 209, Cleanrooms and associated controlled environments.
A list of all parts in the ISO 14644 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
Introduction
This document provides clarification on the application of sound airborne particle sampling techniques
in support of ISO 14644-1:2015 for classification of cleanrooms and clean zones, and ISO 14644-2:2015
for airborne particle monitoring, to provide evidence of cleanroom performance related to air
cleanliness by particle concentration. It provides information on how to gather appropriate, accurate and
repeatable data, and how to interpret this information for the purpose of improving process protection.
This also includes information on the choice of measurement methods and apparatus configuration,
calibration, repeatability/reproducibility and the uncertainty associated with measurement. In short,
what can be reasonably attained with the current technology.
This document addresses potential misinterpretation of the use of ISO 14644-1:2015, C.4.1.2 in
informative Annex C, which suggests the use of limited tubing length for sampling macroparticles. The
phrase in question has been applied beyond the context intended in ISO 14644-1, to other applications.
This document also provides extra clarity on the use of the M Descriptor in ISO 14644-1:2015, Annex C,
specifically in relation to consideration of >5,0 µm alongside ISO Class 5 (EU-PIC/S GMP Grade A and B
at rest).
It provides information on the uncertainty associated with sampling particles ≥5,0 µm and macro-
particles, and measures that can be taken to reduce that uncertainty.
It addresses the importance of understanding that:
— for classification, the quality of the sample is the most important factor;
— for monitoring, the quality of the data is the most important factor;
— direct sampling without tubing is preferred. However, sample tubing is sometimes necessary to get
a representative sample at a significant or critical location;
— to reduce sampling loss in tubing, this tubing is as short and straight as possible;
— a sampling system is evaluated to assess the impact of any compromises in its set up.
An evaluation of existing sampling systems can deem them suitable for continued use even if the system
is assessed as less than optimal.
The scientific basis for airborne particle counting, and the performance characteristics of airborne
particle counters, particularly LSAPC, is amply documented in established technical publications (see
Bibliography).
v
TECHNICAL REPORT ISO/TR 14644-21:2023(E)
Cleanrooms and associated controlled environments —
Part 21:
Airborne particle sampling techniques
1 Scope
This document discusses the physical limitations of probe and particle counter placement, and any
tubing that connects the two, particularly in providing representative samples where particles 5
micrometres and greater are of interest.
The document further identifies the key factors of sampling performance when classifying and
monitoring, and good practice to determine and maintain an acceptable compromise between
attainable accuracy in counting and feasibility of counting in real-life situations.
This document includes a decision tree, used to identify key considerations when sampling airborne
particles, and whether the system requires further assessment. There are also examples provided to
illustrate typical application challenges and show how the decision tree can be used.
It is assumed that this document is read in conjunction with ISO 14644-1 and ISO 14644-2. This
document is not a manual, but an explanatory document. It does not describe measurement methods,
which is handled in ISO 14644-1 and ISO 14644-2, but provides information to help make effective
choices of sampling configuration, when evaluating a new or existing system.
2 Normative documents
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org
3.1
classification
method of assessing level of cleanliness against a specificati
...