Microwave generated steam decontamination of respirators: A thermodynamic analysis

During the two influenza pandemic’s (caused by H1N1 and SARS-Cov-2), over the past twenty years, the use of experimental microwave generated steam (MGS), has shown potential, for decontamination of single-use face respirators and surgical masks. Recent review articles of the decontamination of single-use respirator and face mask has been primarily performed within the health sector, with a particular focus on the disinfection efficiency of the process. However, as with all processing data collected from different research sources, experimental conditions are not reported in a consistent manner. These reports generally provide an overview of MGS microwave conditions with insufficient detail to allow a standard microwave engineering review that enables the thermodynamic of the microwave treatment, to be obtained. The understanding of these parameters and how they influence the decontamination outcome is necessary for further development of the MGS process and enable it to help address some of Green chemistry goals (reduce the amount of harmful chemical products in the environment, and limit the number of respirators and masks required to be manufactured). This review reports on the MGS microwave conditions, then clarifies them in to standard microwave engineering terminology from which the thermodynamic of process can be obtained. In particular how the parameters: power (W), power density (W L-1 ) and process energy budget (J) is reflected in steam generation as well as MGS decontamination of respirator and face mask outcome. The work reviews the treatment of N95-type respirators, surgical and medical masks, and in this context also considers microwave oven-related injuries and mask related fires. Using this knowledge, meaningful recommendations are made on the suitability of individual microwave ovens for decontamination treatment in addition the respirator to the suitability of respirator for use with the MGS decontamination process. Finally, general recommendations are provided for designing a microwave oven for MGS decontamination.