The microbial risk to aseptically manufactured products in pharmaceutical cleanrooms can be
assessed by the use of fundamental equations that model the dispersion, transfer and deposition of
microbial contamination, and the use of numerical values or risk descriptors. This can be done in
two-stages, with the first stage used to assess the transfer of contamination from all of the sources
within the cleanroom suite and the second stage used to assess both air and surface contact
contamination within critical production areas. These two methods can be used to assess and reduce
microbial risk at the preliminary design stage of the cleanroom and associated manufacturing
process or, retrospectively, for an established manufacturing operation
