Ventilatory effects of excessive plastic sheeting on the formation of SARS-Cov-2 in a closed indoor environment

Objective: In this study, we aimed to investigate the ventilatory effect of plastic shields in a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection cluster site using the CO2 tracer technique. Methods: We experimentally investigated indoor air ventilation using the CO2 tracer technique to verify the formation of SARS-CoV-2 infection clusters that erupted in an office space shared by 30 individuals, among whom 11 were infected with SARS-CoV-2. The ventilation frequency was calculated based on the Wells–Riley model and the behavior of infectious aerosols was visualized using thermo-fluid simulation. Results: Observations at several locations revealed extremely low air change rates (0.1/h) in the study site. Local infection clusters were observed several meters away from the door, the only means of ventilation in the office, indicating the negative effect of plastic sheet shielding. The thermo-fluid simulation showed that the plastic sheet blocked the airflow and trapped the exhaled air in each partition cell. Conclusion: Our results verify that opening windows and using fans to blow air out of the window, which led to a considerable improvement in air ventilation (10–28/h) in each partition cell, are suitable methods for lowering SARS-CoV-2 infection risk.