Thursday, February 3, 2011

New Sampling and Classification Methods Set in Revised ISO 14644 Cleanroom Standards

Roberta Burrows, CAE
Diana Granitto
The highly anticipated revisions to the world’s bedrock cleanroom standards are now available from IEST, the Secretariat for ISO Technical Committee 209 (ISO/TC 209): Cleanrooms and associated controlled environments. The newly released ISO/DIS 14644-1—Cleanrooms and associated controlled environments—Part 1: Classification of air cleanliness by particle concentration and ISO/DIS 14644-2—Cleanrooms and associated controlled environments—Part 2: Specifications for monitoring and periodic testing to prove continued compliance with ISO 14644-1 may necessitate a shift in thinking for the controlled environments community.
According to ISO/TC 209 Working Group 1, the global experts who drafted the revisions, new provisions include a simplified classification process based on a more accurate scientific sampling method. The new, statistically-based plan for selecting sample locations calls for a greater number of locations, but in turn eliminates the need to apply a statistical test to the data. This approach reportedly allows for different concentration levels in different parts of the cleanroom and is designed to ensure with a given statistical confidence that at least 90% of the cleanroom area complies with the maximum particle concentration. The new approach provides a risk-based approach to classification that provides interpretable assumptions and conclusions.
The new Draft International Standards (DIS) may be used today as trade references per agreement between customers and suppliers, necessitating an urgent need for an understanding of the revised provisions by those involved in contamination control.The DIS documents are under review by ISO member bodies for voting and comment by May 2, 2011, to provide approval for submission as Final Draft International Standards (FDIS)—the final step before complete replacement of the previous Standards. In the United States, public comments may be submitted to IEST through a form available on the IEST website at The DIS documents are available through IEST Publications.

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