The degree of risk from microbial contamination of manufactured products in healthcare
cleanrooms has been assessed in a series of three articles. The first article discussed airborne sources,
and this second article considers surface contact and liquid sources. A final article will consider all
sources and give further information on the application of the risk method.
The degree of risk to products from micro-organisms transferred from sources by surface
contact, or by liquids, has been assessed by the means of fundamental equations used to calculate the
likely number of microbes deposited (NMD) onto, or into, a product. The method calculates the likely
product contamination rate from each source and gives a more accurate risk assessment than those
presently available. It also allows a direct comparison to be made between microbial transfer by
different routes, i.e. surface, liquid and air
