ISO Technical Report 14644-21, Airborne particle sampling techniques
ISO/TR 14644 Cleanrooms and associated controlled environments – Part 21: Airborne particle sampling techniques, 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. This Technical Report includes information about 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).
Scope of ISO/TR 14644-21
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.
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