Airborne disinfection by dry fogging efficiently inactivates SARS-CoV-2, mycobacteria and bacterial spores and shows the limits of commercial spore carriers for process control

Airborne disinfection of high-containment facilities before maintenance or between animal studies is crucial. Commercial spore carriers (CSC) coated with 106 spores of Geobacillus stearothermophilus are often used to assess the efficacy of disinfection. We used quantitative carrier testing (QCT) procedures to compare the sensitivity of CSC with that of surrogates for non-enveloped and enveloped viruses including SARS-CoV-2, mycobacteria, and spores to an aerosolized mixture of peroxyacetic acid and hydrogen peroxide (aPAA/HP). We then used the QCT methodology to determine relevant process parameters to develop and validate effective disinfection protocols (≥ 4 log10 reduction) in various large and complex facilities. Our results demonstrate that aPAA/HP is a highly efficient procedure for airborne room disinfection. Relevant process parameters such as temperature and relative humidity can be wirelessly monitored. Furthermore, we found striking differences in inactivation efficacies against some of the tested microorganisms.Overall, we conclude that dry fogging a mixture of aPAA/HP is highly efficient against a broad range of microorganisms as well as material compatible with relevant concentrations. Furthermore, CSC are artificial bio-indicators with lower resistance and thus, should not be used for validating airborne disinfection when microorganisms other than viruses have to be inactivated.IMPORTANCE Airborne disinfection is not only of crucial importance for the safe operation of laboratories and animal rooms where infectious agents are handled, but can also be used in public health emergencies like the current SARS-CoV-2 pandemic. We show that dry fogging a mixture of aPAA/HP is highly microbicidal, efficient, fast, robust, environmentally neutral, and a suitable airborne disinfection method. In addition, the low concentration of dispersed disinfectant, particularly for enveloped viral pathogens like SARS-CoV-2, entails high material compatibility. For these reasons and due to the relative simplicity of the procedure, it is an ideal disinfection method for hospital wards, ambulances, public conveyances and indoor community areas. Thus, we conclude that this method is an excellent choice for control of the current SARS-CoV-2 pandemic.