On the risk of infection by infectious aerosols in large indoor spaces

TL;DR

This study investigates aerosol transmission in large indoor spaces, finding that rapid aerosol dispersion and airflow reduce infection risk, emphasizing the importance of masks over aerosol accumulation in such environments.

Contribution

It provides empirical evidence that in large indoor spaces, aerosol dispersion prevents significant accumulation, highlighting the dominance of turbulent dispersion over near-field transmission.

Findings

Aerosol concentrations decrease rapidly regardless of size.

Persistent directional airflow influences aerosol dynamics.

Infection risk from aerosol accumulation is low with proper ventilation and occupancy.

Abstract

Airborne diseases can be transmitted by infectious aerosols in the near field, i.e., in close proximity, or in the far field, i.e., by infectious aerosols that are well mixed within the indoor air. Is it possible to say which mode of disease transmission is predominant in large indoor spaces? We addressed this question by measuring the transport of aerosols equivalent to the size of human respiratory particles in two large hardware stores (V>10000 m$^3$). We found that aerosol concentrations in both stores decreased rapidly and almost independently of aerosol size, despite the different ventilation systems. A persistent and directional airflow on the order of a few cm/s was observed in both stores. Consequently, aerosol dynamics in such open settings can be expected to be dominated by turbulent dispersion and sweeping, and the accumulation of infectious aerosols in the indoor air is unlikely to contribute significantly to the risk of infection as long as the occupancy of the store is not too high. Under these conditions, well-fitting face masks are an excellent means of preventing disease transmission by human aerosols.