Study of changing statistics model’s influence on the exploitation and conformity of results in the new standard version ISO 14644 part 1.

Abstract

Recently, the first two parts of the standard ISO 14644-1 and 2 were updated. This followed a 9-year process of revision. The standard is applicable across several industries covering healthcare, pharmaceuticals and electronics; and it outlines the approach for the design, classification and operation of cleanrooms. This article assesses the influence of the changing ISO 14644-1 on the conformity of the results. The initial version of Part 1 was based on the wrong hypothesis of a Gaussian distribution of particle concentration (in reality, the spatial distribution of particles is random). It is a hypergeometric model that has been selected for the revision of this standard.  If you have seen in the standard ISO 14644-1 of 1999 you will notice that all the calculations are made according to the normal law, like the average, the mean of the averages, the standard deviation and 95% upper confidence limit... then in reality the distribution of the particles in the air in a cleanroom it's random, for this reason in this new version, it is a hypergeometric model that has been selected for the revision of this standard.  In this article we have given a comparison between the two versions of the standard ISO 14644 part 1 and then it has been demonstrated by real case studies that the old version of the standard was based on the wrong hypothesis. After the comparison and study that we have done we encountered a contradiction among two versions of the standard IOS14644-1 (1999 and 2015), that we have treated in the same room, by the end of this experiment we drew out that the room is declared compliant in the new version 2015 and not compliant in the old version 1999, which aroused our curiosity to detect the error in the old version by this real case study.