Tuesday, 23 September 2014

New ISO 14644 Part 1 – draft

A new draft of the international cleanroom standard ISO 14644 Part 1 has been produced. The draft is open for public comments.

With the new draft, the title has been revised to read:  “Cleanrooms and associated controlled environments — Part 1: Classification of air cleanliness by particle concentration”.

The proposed changes from the original 1999 edition are:
  • The initialism (ACP) has been introduced in order to differentiate the airborne particle cleanliness attributes of a cleanroom from other attributes such as surface cleanliness by particle concentration (SCP).
  • The nine ISO cleanliness classes are retained with minor revisions.
  • The major change is the adoption of a more consistent statistical approach to the selection and the number of sample locations.
  • There are also changes to the way that data is evaluated. The revised approach allows each location to be treated independently with a 95 % level of confidence that at least 90 % of the cleanroom or clean zone areas will comply with the maximum particle concentration limit for the target class of air cleanliness.
  • A new concept of a “representative” sample location allows for particle monitoring locations to be either fixed or evenly distributed, or variable and randomly selected. The standard also allows for additional sample locations to be added to the minimum number of sampling locations.
  • The statistical confidence is therefore not based on confidence intervals in the normal distribution. Instead it relates to the process by which the measuring locations are selected.

Copies of the draft are available from national standards agencies.

Posted by Tim Sandle