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Part 3 of ISO 14644 describes test methods and requirements for measuring instruments and procedures used to determine the performance parameters of cleanrooms and clean zones, with the exception of the following air cleanliness classification tests:
- Airborne particulate cleanliness (APC) classification, according to NF EN ISO 14644-1;
- Surface particulate cleanliness (SPC) classification, according to NF EN ISO 14644-9;
- Airborne chemical cleanliness (ACC) classification, according to NF EN ISO 14644-8.
Tests concerning microbiological contamination are addressed in NF EN ISO 14698-1, NF EN ISO 14698-2 and NF EN 17141.
Cleanroom or clean zone qualification can be carried out in the following three possible occupancy states: As-Built, At-Rest and Operational, or during the following stages:
- Renovation or revamping works;
- Requalification:
- following a modification to the cleanroom or its intended use;
- after the detection and correction of a defect;
- during periodic inspections.
This part of the standard also specifies typical requalification intervals depending on the various tests. These intervals were previously included in the former NF EN ISO 14644-2 standard, dated 2000. The revised version of February 2016 focuses only on monitoring the continued performance of the cleanroom with regard to airborne particulate cleanliness.
The revision of ISO 14644-3 is based on several factors:
The first edition of Part 3 dates from March 2006 for the NF EN ISO collection, or December 2005 for the ISO version. It therefore entered the usual revision process after five years.
- The broader evolution of the ISO 14644 series:
Revision of Parts 1 and 2, with new ISO versions published in December 2015 and incorporated into the French Afnor standards collection at the end of February 2016.
The standards were divided into two major families: standards for classifying and quantifying cleanliness levels, such as ISO 14644-1, -8, -9 and -10, and standards based on methodological approaches, such as ISO 14644-2, -4 and others.
- New areas of work related to test methods, such as ultrafine particles and particle deposition;
- Technical modifications required to update the content of the current version of the standard, which was developed in the early 2000s.
The reference method for airborne particulate classification is provided in normative Annex A of ISO 14644-1. Consequently, all information relating to the measurement of airborne particle concentrations, including microparticles (see informative Annex C), has been incorporated into the new Part 1 of ISO 14644.
Recommendations concerning the characteristics of particle counters have also been transferred to Part 1 of ISO 14644 (see paragraph 3.5 and informative Annex F), with reference also made to ISO 21501-4:2007.
Information relating to the measurement of ultrafine particle concentrations has been transferred to the ISO 14644-12 project, which addresses particles with diameters below the specified threshold.
The recommended frequencies for supplementary tests that were included in the former ISO 14644-2 standard (the November 2000 standard) are now mentioned in the draft ISO 14644-3 (Table B).
Three specific metrology terms have been introduced in the revision draft: Resolution, Maximum Permissible Error (MPE), and Sensitivity.
The list of classification tests includes:
- Classification tests for cleanrooms and clean zones;
- Airborne particulate cleanliness (APC) classification;
- Surface particulate cleanliness (SPC) classification;
- Airborne chemical cleanliness (ACC) classification;
- Surface chemical cleanliness (SCC) classification.
Control frequencies:
- Differential pressure: 12 months;
- Airflow rate (non-unidirectional airflow installations) / Air velocity (unidirectional airflow installations): 12 months;
- Filter integrity testing: 24 months;
- Temperature / relative humidity: 12 months.
The main changes concern the transfer of test methods related to particle concentrations to the standards dealing with the classification of the different types of cleanliness.
In general, the changes between the current and revised versions provide additional information to the existing text, although some sections have also been simplified, which may lead to misinterpretation.
However, certain technical points have not yet reached consensus and require further discussion.
The initial objective was to publish the new version of Part 3 relatively soon after the publication of the revised ISO 14644-1 and ISO 14644-2 standards. This objective has since become increasingly difficult to achieve. Practical challenges were expected for stakeholders applying the methods described in the current NF EN ISO 14644-3:2006 alongside the revised NF EN ISO 14644-1 and -2 standards of 2016, potentially leading to a challenging transitional period.
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