Moisture content target level

The significance of this model is that it describes the optimal situation for water permeation into the spore and therefore ethylene oxide permeation to its target site as a function of the moisture content of the spore and the relative humidity of the environment during exposure. The rate of microbial inactivation therefore increases (as long as all other factors are held constant) with increased relative humidity during exposure. Kaye and Phillips [4] demonstrated a 33% RH optimum for microbial inactivation as a result of exposure to ethylene oxide. In practical situations it is better to err on the side of too much rather than too little moisture. With industrial-scale ethylene oxide sterilization, humidity levels are usually in the range of 50% to 60% RH. The upper limit is usually dictated by deleterious effects on packaging. 

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