Dispersion and risk assessment of airborne contaminants in pharmaceutical clean rooms

University dissertation from Institutionen för byggnader och installationer

Abstract: In many of today's industries, particularly in the healthcare field, special protection is required against airbornemicrobiological contamination. Clean rooms and clean zones areused to separate the ambient environment from contaminationcontrolled areas. In clean rooms and clean zones, especially inthe pharmaceutical industry, the inherently low levels ofmicrobial contamination make measurement of contaminationdifficult. The most critical environment within pharmaceuticalfacilities are commonly so low in contamination that the bestavailable microbial monitoring equipment must operate at orbelow its limit of detection.People are the principal source of airborne microbialcontamination within clean rooms. In studies described in thisthesis the emission of contamination by humans dressed inmodern clean room clothing systems, has been studied using aspecially designed dispersal chamber. The contamination emittedby gowned humans has been estimated and is significantly lowerthan those previously published.Results from microbiological methods for sampling airbornecolony forming units (CFU) are shown to correlate with thespecific instrument used to conduct the measurements and arenot absolute values. Because viable particles in air dispersevia the same mechanism as non-viable particles, the airbornemicrobiological contamination risks can be evaluated in amanner similar to those used to control contamination risksfrom airborne particulate contamination.Theoretical aspects of particulate dispersion in air streamsas well as studies of factual situations give that thecontamination risks are mainly dependent upon the velocityfield and the concentration of airborne contaminants: hence theinteraction between air movements and dispersion ofcontaminants is of vital importance. The necessary movements ofpeople and machinery in the industrial clean room setting makethe analysis of risk situations complex.A specific analytical method for microbiological riskassessment of airborne contaminants in clean zones is describedand experiences with the method are discussed. The method forlimitation of risks (LR-Method) uses a non-microbiologicalapproach. The method utilises the visualization of airmovements, a challenge test with particles, and determinationof a risk factor for the evaluationof potential risks ofairborne microbial contamination.Key-words:airborne contamination, clean rooms, cleanzones, clothing systems, dispersion of contaminants, LR-Method,microbiological risk assessment, risk assessment, sourcestrength.

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