Effects of temperature and relative humidity on biological indicators used for ethylene oxide sterilization

Abstract

A study was made to determine the effects of temperature and moisture on the D-value of a common biological indicator. Relative humidity (RH) was varied between 10 and 70% in increments of 10%, and temperature was varied between 30 and 70°C in increments of 10°C. Temperature was found to have a pronounced effect on the D-value. At 60% RH, the D-value varied from 15.0 min at 30°C to 1.1 min at 70°C. When RH was plotted against the average D-value at the various temperatures, the temperature curves at or above 50°C were more erratic and the RH had a significant effect. The study showed that temperature and RH must be controlled if biological indicators are to be properly calibrated for use in ethylene oxide sterilization.