ISO/TR 14644-21:2023

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.