It is well established that humans are the biggest source of contamination in cleanrooms, irrespective of whether that contamination arises from airborne particles or is microbiological. The key function of cleanroom garments, therefore, is to protect clean processes from the contamination from personnel and their clothing. Their effectiveness in doing this has been shown in a very extensive study carried out in 2010 using a particle counter in a ‘Body Box’. Another recent study looked at how the average particle release per minute of an employee varied based on the garment being worn and the movement being performed, the results of which are summarised in Table 1.
From a microbiological point of view, this study begs the question whether any conclusion can be made based on these figures regarding possible microbiological count. However, this question could not be empirically tested or proven with the results available at that time.
There are studies in the literature on this topic that derive a theoretical connection, but to date there has been no study that provided test results of microbial release in a similar way to that of particle release, measured with a particle counter. This task caught the attention of Dastex and a further Body Box study was made in 2014.
The crucial factor for the feasibility of the study was the introduction of a new measuring device supplied by TSI: the Biotrak 9510-BD. With this particular counter it was now possible to quantitatively record and evaluate airborne germs. Interestingly, the Biotrak device can record quantitatively not only airborne germs but also airborne particles, therefore the results could be separated into viable and non-viable contamination.
An interesting question that arose was whether there is a direct correlation between the contamination coming from humans and the microbial release of the person in the study; if so a kind of conversion factor could be obtained.
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