ABSTRACT
The efficiency of the RTP is dependent on the accurate presentation of the two arrowhead seals, nose to nose. Naturally, the seals cannot come to a true point, and the whole port is subject to both engineering tolerances and to wear in use. Thus, there is a ring at the nose of the seals in which contamination may potentially be exchanged. Even in the best-engineered port, this ring might be 0.1 mm across, and in a port of, say, 350-mm diameter, this represents a total area of some 55 mm2, on which a considerable number of microorganisms might reside.
