Effects of chemically-reductive gas contaminants on inactivation of airborne viruses by non-thermal plasma

As the threats of airborne infectious disease outbreaks emerged worldwide, non-thermal plasma (NTP) has the ability to control airborne virus transmission, whose inactivation effectiveness on bacteriophage MS2 has been verified by previous studies. However, the existence of chemically reducing air pollutants from sources such as livestock may have a negative impact on the role of oxidizing species in the NTP inactivation process. In this study, a packed-bed dielectric-barrier discharge NTP device was used to inactivate MS2, with a plasma power supply at a peak-to-peak voltage of 20 kV and a discharge power of 1.7 Watts. Ammonia and hydrogen sulfide were added to the airflow containing MS2 aerosols, which then passed through the NTP device and were exposed to plasma for a contact time of <0.5 seconds. The NTP inactivation efficiency of MS2, in the units of log plaque-forming-units per milliliter of sample (logPFU/mL), was calculated by performing plaque-assay analyses to enumerate culturable virus concentrations, and excluding physical losses of virus samples from the packed bed. It was found that at the concentration level of 1 ppm, both NH₃ and H₂S have shown a statistically-negative impact on the NTP inactivation efficiency of MS2 virus, by lowering the NTP inactivation efficiency from 1.04 log PFU/mL for the no-gas-addition control to 0.48 and 0.51 log PFU/mL respectively. This efficiency-lowering effect highlights the importance of chemically-reductive gas contaminants in NTP inactivation.