Indoor airflow effect on the detectability of airborne pathogens: Simulation with computational fluid dynamics and...

Detecting airborne pathogens (bioaerosols), such as bacteria and viruses, in multi-use facilities is important to prevent infection through the air. To that end, a sufficient volume of air is necessary to detect pathogens with polymerase chain reaction (PCR) tests. However, determining positions at which air samplers should be located in such facilities can be challenging. In this work, we performed case studies in an office for students, in which a ceiling-type air conditioner and an air purifier were installed, to evaluate the effects of indoor airflow on the detectability of airborne pathogens. Airflow patterns and trajectories of saliva droplet aerosols generated by an infected person were investigated to estimate the number of aerosols entering each air sampler. The airflow patterns strongly influenced the spatial distribution of droplet aerosols, which led to pronounced variations in the sampling results. Locating air samplers in air flow recirculation regions consistently yielded the highest sample concentrations, which suggests that aerosols were not uniformly dispersed throughout the space but instead were accumulated in specific regions due to the influence of airflow. Consistently, during long-term air sampling, infectious bioaerosols (influenza A, HCoV-229E, and Bordetella pertussis) were detected with PCR tests in regions where the flow was recirculated, but not where it was stagnant. These results demonstrate that airflow patterns influence the distribution of bioaerosols in the air, which leads to the accumulation of aerosols in specific areas. Therefore, selecting sampling locations strategically is essential to detect airborne pathogens in indoor environments and also to place mitigation devices.