. The Canadian nurse. lein the literature with regard to itsactivity at elevated temperatures, inspite of the fact that commerciallyproduced equipment operates at 130° was for this reason that we em-barked on a program to determinemore accurately the relationship be-tween temperature, gas concentration,relative humidity and time for steril-ization. Figure 1 shows killing time curvesfor populations of x 10* sporesof Bacillus globigii in two concentra-tions of ethylene oxide. It will benoticed that these data confirm thework of Phillips and Kaye with regardto the concentration dependence
. The Canadian nurse. lein the literature with regard to itsactivity at elevated temperatures, inspite of the fact that commerciallyproduced equipment operates at 130° was for this reason that we em-barked on a program to determinemore accurately the relationship be-tween temperature, gas concentration,relative humidity and time for steril-ization. Figure 1 shows killing time curvesfor populations of x 10* sporesof Bacillus globigii in two concentra-tions of ethylene oxide. It will benoticed that these data confirm thework of Phillips and Kaye with regardto the concentration dependence at lowtemperatures. As the temperature in-creases, however, the dependence onconcentration diminishes until a criticaltemperature is reached for a particularconcentration. At this point any in-crease in concentration has no effecton the rate of kill of bacterial ethylene oxide concentrations of440 provide a slower sterilizingaction than concentrations of 880 only at temperatures below 110° Fig. 1. Effects of concentrationand temperature Above this point there is no differencein the rates of sporicidal action ofthe two concentrations. The influence of temperature on thesterilizing action of ethylene oxideis quite drastic between room temper-ature and 110°F. Above the range of100°-110°F, however, less gain inrate of kill is evident and the practicalvalue of higher sterilizing tempera-tures is questionable. In any case, areasonable sterilizing time is obtainedat temperatures above 100°F. Thespores previously mentioned are des-troyed in less than 40 minutes. The relative humidity (RH) of theatmosphere plays an important rolein the action of ethylene oxide. Therate of kill of microorganisms dimi-nishes severely as the relative humiditydrops below 20 per cent. Althoughthere is some decrease in rate of killas the relative humidity increases to100 per cent, the added time is notsignificant in relation to the timeof the cycle. Therefore, it is co
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