But how can we ensure that protective garments are not themselves vehicles of contamination? And how can we ensure that cleaning and sterilization processes are effective and do not alter the characteristics of the garments? We attempted to answer these questions, concentrating our attention mainly on glasses (in general, on individual protection devices usually referred to as masks).

Because glasses are not disposable, we must consider that stress conditions such as repeated sterilizations may compromise their use. The glasses may lose functionality and the components might be damaged, resulting in the release of contaminating material.

Figure 1: The type of glasses evaluated

We chose to verify only the steam-sterilization cycle because it is the process most commonly used in the pharmaceutical industry, although glasses also are sterilized using other methods (γ-rays, ethylene oxide, etc.).

Table I: Characteristics of the glasses used.

The effectiveness of the sterilization process is a probabilistic function depending on the number of microorganisms present, the thermic resistance of these microorganisms, and the quantity of heat supplied. Therefore, determining the quantity of heat that is necessary to attain the 12-log reduction in the microorganism population to ensure sterility depends entirely on the thermic resistance of the present microorganisms.

Table II: Glasses subjected to steam sterilization cycles.