Victor John Law

Abstract

During the two influenza pandemic’s of this century (caused by H1N1 and SARS-Cov-2), experimental microwave generated steam (MGS), has shown potential, for decontamination of respirators and surgical masks. Recent review articles of the decontamination of single-use face respirators / masks have been primarily performed within the health sector, with particular focus on the disinfection efficiency of the process. However, as with all datasets collected from different research sources, experimental conditions are not reported in a consistent manner. These reports generally provide an overview of MGS microwave conditions, however they did provide sufficient detail in standard microwave engineering terminology from which the thermodynamic of process can be obtained. In particular how the parameters: power density (W L-1) and available energy budget (J s-1 x J = J) is reflected in the processed respirator / mask outcome. 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 fulfill 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. The work reviews the treatment of N95-type respirators, surgical and medical masks, and in this context looks at microwave oven-related injuries and fires. In addition, the thermodynamics of converting liquid-phase water into steam in terms of available microwave power (W) calculated power density (W/ft3, W L-1) and process energy budget verses the decontamination outcome. Using this knowledge, meaningful recommendations can be made on the suitability of individual microwave oven for the treatment, in addition what respirators should be used, or not be used in MGS decontamination process. Finally, if an oven cannot be found, then recommendation for how to go about designing a microwave oven for MGS decontamination is given.