Development and quantification of H2O2 decontamination cycles.

Whereas correlation of physical process parameters with bacterial reduction is well established in thermal sterilisation, such a method is currently neither generally recognised nor possible for H2O2 decontamination. As a result, the efficiency and reproducibility of H2O2 decontamination and the course of the process over time can at present only be ascertained, verified, and documented using a microbiological system. Based on the "Fractional Negative" method of determining the D-values of Biological Indicators (BIs), which is contained in the ISO 11138-1 and EN 866-3 standards, a complete and systematic method is presented that enables the parameters for each cycle phase to be determined and verified, and the effectiveness of the process to be quantified. The method also enables differences in bacterial reduction between positions which can be effectively decontaminated and "worst case" positions to be quantified, so that, using the results, the process can be individually adjusted to specific overall bacterial reduction requirements. The new method also specifies the procedure for assessing the suitability of the microbiological system used prior to qualification and validation a condition sine qua non if process parameter studies are to be used to establish and document a decontamination cycle. With the aid of practical experimental data, this paper presents in detail the individual stages involved in the method proposed for decontamination cycle development, and interpretation of the results and their implications for the process parameters. In particular, it is shown that bacterial reduction is only stable over time under certain conditions, and that doubling the decontamination time does not result in doubling of kill effect. Moreover, the method makes it possible to react to any fluctuations in resistance in the microbiological system employed, which occur during requalification of the process.