Computational fluid dynamics simulation of SARS-CoV-2 aerosol dispersion inside a grocery store.

Grocery stores provide essential services to communities all over the world. The COVID-19 pandemic has necessitated better understanding of the transport and dynamics of aerosolized viruses, particularly for the assessment of infection transmission risk within grocery stores and for other providers of essential services. In this study, a 3D computational fluid dynamics model was developed for a medium-sized grocery store in the United States using Ansys Fluent software. Different cases were simulated of a single infected person releasing viral aerosols with and without wearing a face mask. Results showed characteristic airflow and temperature distribution patterns inside the store that can drive the indoor dispersal of viral aerosols. Unsteady spatial distribution of mean age of air was used as a metric to indirectly quantify areas of higher risk of infection. Several factors affected the localization of suspended viral aerosols. Major recirculation patterns in certain locations of the store caused by persistent eddies were primarily attributed to increased mean age of air. The maximum mean age of air in the grocery store was found to be less than 30 min. Simulation results indicate that, without wearing a face mask, the aerosol particles released from a coughing infected person can be spread throughout nearly one-quarter of the grocery store in less than 6 min. The source-control strategy with a face mask showed significant reduction of viral aerosols being dispersed indoors.

Multizonal modeling of SARS-CoV-2 aerosol dispersion in a virtual office building.

The dispersion of indoor airborne contaminants across different zones within a mechanically ventilated building is a complex phenomenon driven by multiple factors. In this study, we modeled the indoor dispersion of airborne SARS-CoV-2 aerosols within a US Department of Energy detailed medium office prototype building using CONTAM software. The aim of this study is to improve our understanding about how different parts of a building can experience varying concentrations of the airborne viruses under different circumstances of release and mitigation strategies. Results indicate that unventilated stairwells can have significantly higher concentrations of airborne viruses. The mitigation strategies of morning and evening flushing of conditioned zones were not found to be very effective. Instead, a constant high percentage of outdoor air in the supply mix, and the use of masks, portable HEPA air cleaners, MERV 13 or higher HVAC air filters, and ultraviolet germicidal irradiation disinfection were effective strategies to prevent airborne viral contamination in the majority of the simulated office building.

Reducing Airborne Infectious Aerosol Exposure

Since beginning its work in late March 2020, the ASHRAE Epidemic Task Force (ETF) has produced a large set of guidance documents totaling hundreds of pages, all of which can be found at the ASHRAE COVID-19 resources web pages (www.ashrae.org/COVID19). This guidance has evolved as scientific understanding has increased and circumstances have changed, necessitating several updates. The initial, one-page "Core Recommendations" document, approved in January 2021, was written to provide a concise summary of the most current task force recommendations for the benefit of the public and to promote consistency between guidance documents developed by different ETF teams. This column includes the Core Recommendations (in bold) with added commentary to provide the rationale for each.