Transport and Fate of Virus-Laden Particles in a Supermarket: Recommendations for Risk Reduction of COVID-19 Spreading

Abstract

The transport of virus-laden particles was investigated numerically in an archetypical supermarket configuration of area 1,200 m2 and ceiling height of 4.5 m. The particles were tracked using a Lagrangian particle tracking code coupled with the computational fluid dynamics (CFD) model Ansys Fluent. Air transport was assumed to occur due to indoor ventilation. Flow dynamics were simulated using the Reynolds-averaged Navier Stokes (RANS) approach. The movement and spreading of 5- and 20-μm particles were studied with 0%, 25%, and 100% attachment efficiencies on surfaces in the supermarket. We found that the indoor airflows can significantly enhance the transport of particles (e.g., >15 m for 5 μm, and >5 m for 20 μm); therefore, the 6-ft (2.0 m) social distance recommended by health experts would not be sufficient to prevent the transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We found that the attachment on surfaces reduces the transport of particles significantly within the supermarket, and that an attachment efficiency of 25% results in transport similar to that resulting from 100% efficiency. This suggests that the type of surfaces is not crucial in terms of air transport of particles. We support the existing approaches for reducing exposure between people through the adoption of one-way movement within an aisle. However, we also propose placing display shelves within the aisles in a staggered way to form baffles that would both increase the surface area and block the transport of airborne particles. We found that virus-laden particles could be sucked into the ventilation system through return vents, and could pose potential infection risks for the buildings connected to the same ventilation system. Hence, high-efficiency particulate air (HEPA) filters and pleated filters with a minimum efficiency reporting value (MERV) greater than 12 are recommended.