ISO revises cleanroom standard on performance test methods

The latest cleanroom test methods are highlighted in the newly issued ISO Draft International Standard (DIS) 14644 Cleanrooms and associated controlled environments — Part 3: Test methods. This update of the 2005 Standard has been modified to align with the recent landmark revisions of 14644 Part 1: Classification of air cleanliness by particle concentration and Part 2: Monitoring to provide evidence of cleanroom performance related to air cleanliness by particle concentration.

ISO/DIS 14644-3 sets out appropriate test methods for measuring the performance of an installation, a cleanroom, or an associated controlled environment.

Daniel Dennison, manager of Precision Air Technology and the longtime US expert to Working Group 3 of ISO/TC 209, points to several noteworthy changes in the document:

• Transfer of the tests for classification of cleanliness by particle concentration from 14644-3 to 14644-1 (for macroparticles) and 14644-12 Classification of air cleanliness by nanoscale particle concentration (for nanoscale particles, formerly defined as ultrafine particles)
• Significant changes to the procedure for the installed filter system leakage scan test using a discrete-particle counter (DPC) to verify the installation, filters, and grid system are free of defects and leaks; and
• The addition of a segregation test methodology to assess the protective effect of a specific segregating airflow, for example, across a doorway or across the perimeter of an area with a higher classification than the surrounding area. The test is performed by generating a sufficiently higher concentration in the lesser classified area (downstream side), measuring this as the reference concentration, and counting the particle concentration just across the perimeter in the protected area (upstream side).

Intended for use by certifying companies and end users alike, ISO/DIS 14644-3 specifies performance tests for two types of cleanrooms (unidirectional and non-unidirectional) in three occupancy states (as-built, at-rest, and operational). Principles, selection guidelines, procedures, and required apparatus are outlined for the following tests:

• Air pressure difference—to verify the cleanroom system can maintain the specified pressure differential between the installation and its surroundings
Airflow —to determine supply airflow volume flow rate in a non-unidirectional cleanroom and air velocity distribution in a unidirectional cleanroom
• Airflow direction and visualisation —to confirm airflow direction, airflow pattern, or both in regard to specifications
• Recovery—to verify the installation can return to a specified cleanliness level within a finite time, after being exposed briefly to a source of airborne particulate challenge
• Temperature and humidity—to demonstrate the cleanroom air-handling system can maintain specified air temperature and moisture levels
• Installed filter system leakage—to confirm the final high-efficiency air filter system is properly installed
• Containment leak—to detect intrusion of unfiltered air into the cleanroom from outside the cleanroom
• Electrostatic and ion generator—to evaluate electrostatic voltage levels on objects, static-dissipative properties of materials, and performance of ion generators
• Particle deposition—to measure surface concentration, quantity, or effects of particles deposited upon surfaces at any orientation
• Segregation—to assess the separation effectiveness achieved by a specific airflow

This is the public’s first look at the revised test methods of the ISO 14644 series following the revision of Parts 1 and 2.

ISO/DIS 14644-3 is being reviewed globally by ISO/TC 209 national member bodies during the three-month Draft International Standard ballot.

This new document, along with all of the ISO 14644 Cleanroom Standards, is available from IEST, the Secretariat to ISO Technical Committee 209 (ISO/TC 209).

In the US, technical experts should provide feedback by February 10, 2017 to IEST as the Administrator to the United States Technical Advisory Group (US TAG) to ISO/TC 209.