2020/06/20 by Eric G. Blackman, Gourab Ghoshal, Blackman, Eric G. +1
Engineering · Mathematics · Medicine · #Atmospheric and Oceanic Physics (physics.ao-ph) #COVID-19 epidemiological studies #Chaotic Dynamics (nlin.CD) #Evacuation and Crowd Dynamics #FOS: Physical sciences #Fluid Dynamics (physics.flu-dyn) #Infection Control and Ventilation #Physics and Society (physics.soc-ph)
paper · pdf · doi:10.48550/arxiv.2006.11651
openalex publication_date 2020/06/20 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
To mitigate the SARS-CoV-2 pandemic, officials have employed social\ndistancing and stay-at-home measures, with increased attention to room\nventilation emerging only more recently. Effective distancing practices for\nopen spaces can be ineffective for poorly ventilated spaces, both of which are\ncommonly filled with turbulent air. This is typical for indoor spaces that use\nmixing ventilation. While turbulence initially reduces the risk of infection\nnear a virion-source, it eventually increases the exposure risk for all\noccupants in a space without ventilation. To complement detailed models aimed\nat precision, minimalist frameworks are useful to facilitate order of magnitude\nestimates for how much ventilation provides safety, particularly when\ncircumstances require practical decisions with limited options. Applying basic\nprinciples of transport and diffusion, we estimate the time-scale for virions\ninjected into a room of turbulent air to infect an occupant, distinguishing\ncases of low vs. high initial virion mass loads and virion-destroying vs.\nvirion-reflecting walls. We consider the effect of an open window as a proxy\nfor ventilation. When the airflow is dominated by isotropic turbulence, the\nminimum area needed to ensure safety depends only on the ratio of total viral\nload to threshold load for infection. The minimalist estimates here convey\nsimply that the equivalent of ventilation by modest sized open window in\nclassrooms and workplaces significantly improves safety.\n