Hybrid and independent gaseous oxidation: new insights into oxidant stability and microbial inactivation properties

The demand for effective and sustainable disinfection technologies has accelerated interest in oxidation processes for healthcare and environmental applications. In this study, the decomposition behaviours and decontamination efficacies of gaseous ozone, vaporised hydrogen peroxide (VHP), and vaporised peracetic acid (VPAA) were evaluated on porous surfaces, both individually and in hybrid combinations . We quantify the kinetics of gaseous/vaporised oxidant decomposition and realise that monochromatic UVC radiation accelerates oxidant decomposition compared to polychromatic UVC radiation; whereas the interactions of the oxidants have both decomposition and stabilising effects. Staphylococcus aureus was selected as a representative pathogen, and inactivation was quantified following controlled exposures in a bespoke chamber. Results showed that the performance of the oxidants varied with process conditions. At low oxidant doses (< 200 ppm.min), none of the individual oxidants were significantly effective in inactivating S. aureus , resulting in < 2 log 10 reduction; however, ozone outperformed all oxidants in this dose range. Hybridising the oxidants significantly improves performance, with ozone + VPAA and VHP + VPAA achieving the highest log reductions (7 log 10 ) compared to the single-oxidant and other hybrid systems. These findings indicate that hybridising gaseous oxidants can overcome limitations of single oxidants by leveraging apparent synergistic chemical interactions, thereby enhancing decontamination efficacy. Additionally, we find that hybrid oxidant systems can shift between accelerated decomposition and retarded decomposition depending on oxidant sequence. While such hybrid approaches have predominantly been used for water treatment, this study provides new insights into the stability, transport, and interactions between oxidants and with contaminated porous materials in the gaseous phase. Thus, hybrid oxidation is a promising surface decontamination strategy that supports infection control measures and sustainable material reuse.