2002 Volume 72 Issue 9 Pages 423-428
Sterilization steam in hospitals often includes non-condensable gases (NCG's) like carbon dioxides, nitrogen and oxygen. Because NCG's do not condense in the steam sterilization process even after they come in contact with sterilization objects, this sometimes causes sterilization failures. The specified volume ratio of NCG sterilization steam, after condensation, is defined to be less than 3.5% by EN and ISO standards (to maintain a machine operated under normal conditions). Although it is recognized, in general, that air evacuation is important in sterilization, the effects of NCG's in steam remains to be discussed in Japan. AAMI recommends a daily inspection of the air evacuation process by a Bowie-Dick type test. However when use this test without considering NCG's, we may make mistakes in the accurate judgement of the conditions of the machine. In this study, we measured NCG's that were included in sterilization steam using the standard method of EN 285. These results indicated that NCG's were over 7 % in a particular case and that the discoloration degree of the Bowie-Dick type test was different. We propose a method to improve this situation considering the fact that NCG's concentration decreases to the degree, which satisfies EN 285 standards using high steam pressure in the water.
