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Important Revision to ISO 14644-1

By: Mike Venanzi

The second edition ISO 14644-1:2015, cancels and replaces the first edition, ISO 14644-1:1999. It has been technically revised throughout. These changes are in response to user and expert feed-back validated by international inquiry.

The most significant change which will have the greatest impact to the sampling conducted at our Sponsor’s facilities is as follows.  A new and more consistent statistical approach is used for the selection and the number of sampling locations. In addition, evaluation of the data collected is covered.

With ISO 14644-1:1999 an underlying assumption was that the particle counts follow the same normal distribution across the room. This assumption has now been discarded to allow the sampling to be used in rooms where the particle counts vary in a more complex manner.

The minimum number of sampling locations required with ISO 14644-1:1999 has been changed.  The minimum number of sampling locations was previously determined by taking the square root of the measurement area (in square meters).  A reference table is now provided to define the minimum number of sampling locations required based on a practical adaptation of the sampling model technique.  This change results in a moderate increase in the number of sampling locations to be taken.

Using the minimum number of sampling locations provides at least 95% confidence that at least 90% of the cleanroom or clean area does not exceed the class limits.  The room is divided so that each selection within each section of a sampling location is considered to be representative of the characteristic of the section.  This change will result in an increased number of sample locations, changes to maps currently being used and changes to raw data and final reports.