･This study aimed to visualize and measure the flow field of aerosols derived from exhalation (jet flow) during face-to-face encounters with another person and to clarify the viral exposure risk when passing by another person.
･Furthermore, we compared the behavior of the flow fields of aerosols during face-to-face encounters under ventilated versus non-ventilated conditions to assess the aerodynamic characteristics of ventilation and its impacts on the viral exposure risk.
･The peak risk of viral exposure occurs within a 5-s window during face-to-face interactions, irrespective of whether ventilation is adequate or lacking.
Abstract
The link between aerosol dynamics and viral exposure risk is not fully understood, particularly during movement and face-to-face interactions. To investigate this, we employed Particle Trace Velocimetry with a laser sheet and a high-speed camera to measure microparticles from a human mannequin’s mouth. The average peak time in the non-ventilated condition (expiratory volume, 30 L; passing speed, 5 km/h) was 1.33 s (standard deviation = 0.32 s), while that in the ventilated condition was 1.38 s (standard deviation = 0.35 s). Subsequently, the microparticle count decreased. Similarly, the microparticle count in the ventilated condition (30 L; 5 km/h) peaked within approximately 5 s (~ 1.17 s) and decreased thereafter. A similar trend was evident across other expiratory volumes (55 L, 80 L) and passing speeds (10 km/h, 15 km/h, 20 km/h) in both the non-ventilated and ventilated conditions. Our results showed that the peak of viral exposure risk was within 5 s during face-to-face encounters under both ventilated and non-ventilated conditions. Moreover, the risk of viral exposure greatly decreased in ventilated conditions compared to non-ventilated conditions.
Benefit
This study visualized and measured the flow field of aerosols derived from exhalation (jet flow) during face-to-face encounters with another person and clarified the viral exposure risk when passing by another person. We employed a full-scale mobile mannequin and a Particle Tracking Velocimetry (PTV) system in what is considered the world’s first such attempt. Our findings demonstrate that the peak risk of viral exposure occurs within a 5-s window during face-to-face interactions, irrespective of whether ventilation is adequate or lacking. This study has implications for reducing aerosol-mediated transmission of various pathogens, such as SARS‑CoV‑2, influenza, and monkeypox.
Market Application
A full-scale mobile mannequin and a Particle Tracking Velocimetry (PTV) system which can visualize and measure the flow field of aerosols derived from exhalation. Additionally considering a risk mitigation strategy for the duration of 5 s during face-to-face encounters is expected to significantly reduce the risk of virus exposure in airborne transmission.
Publications
https://www.nature.com/articles/s41598-023-44967-x
