Measuring Steam Composition According to Standards: Is the Method Sufficiently Specified?

Together with temperature and time, steam composition, i.e. the fraction of non-condensable gases (NCGs) and water vapour in steam, is an essential parameter to be monitored during a steam sterilization process. In the current standards, only EN 285:2015+A1:2021 provides a test method for the quantification of NCGs and specifies an upper limit for the NCG fraction admissible in the sterilizer's steam pipes. However, it provides no indication of steam collection timing or condensate amount. This study aimed to investigate whether this lack of specification affected measurements and test outcomes. Three different processes were run in a medium-sized steam sterilizer. The volumes of NCGs and steam condensate were measured every 30 seconds from the start of the process to the end of the exposure phase. Data were analysed to provide NCG% measurements (i.e., mL of NCGs in 100 mL of steam condensate) at different time points during the processes and using different condensate volumes. The results pointed out the dependence of NCG % and test outcomes on both the time of measurement and the amount of the collected condensate. The lack of specifications in the current test methods leads to non-univocal NCG values that are poorly informative of steam composition and cannot be used for comparison to a recommended threshold. New technologies that are able to monitor steam composition quantitatively in real-time in every process are advocated for improving the safety of processed devices.