IEST paper clarifies revision to ISO Cleanroom Standards


Aims to help cleanroom users understand new air sampling plan in new cleanroom standards

A technical paper recently published by the US Institute of Environmental Sciences and Technology (IEST) can help any industry that uses cleanrooms to understand a new air sampling plan described in the recently released Draft International Standard (DIS) versions of the ISO cleanroom standards.

The paper, published as a Special ISO Edition of the Journal of the IEST, was written by members of ISO Technical Committee 209, Working Group 1 (ISO/TC 209, WG 1), the experts who developed 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.

The IEST says it is imperative for those involved in cleanroom operations to understand the procedural changes contained in ISO/DIS 14644-1 and ISO/DIS 14644-2, as well as the rationale for those changes, for several reasons.

First, the DIS may now be used worldwide as trade references – and so may the original standards.

When deciding which version of these standards to use, the IEST says customers and suppliers should both be aware that the new DIS documents provide 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.

Second, the DIS documents are under review by ISO member bodies for voting and comment. US users of these documents are encouraged to submit comments up until 15 April to IEST at

The technical paper, Sampling Plan for Cleanroom Classification with Respect to Airborne Particles, is available for free download from the IEST website.