Size dependent infectivity of SARS-CoV-2 via respiratory droplets spread through central ventilation systems

Journal Article · 18 February 2022 · International Communications in Heat and Mass Transfer

DOI: https://doi.org/10.1016/j.icheatmasstransfer.2021.105748 · OSTI ID:1845842

Pease, Leonard F. ^[1]; Salsbury, Timothy ^[1]; Anderson, Kevin K.  ^[1]; Underhill, Ronald M. ^[1]; Flaherty, Julia E. ^[1]; Vlachokostas, Efthimios Alexandros  ^[1]; Burns, Carolyn AM ^[1]; Wang, Na  ^[1]; Kulkarni, Gourihar R.  ^[1]; James, Daniel P. ^[1]

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1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

In this work, we evaluate the transport of respiratory droplets that carry SARS-CoV-2 through central air handling systems in multiroom buildings. Respiratory droplet size modes arise from the bronchioles representing the lungs and lower respiratory tract, the larynx representing the upper respiratory tract including vocal cords, or the oral cavity. The size distribution of each mode remains largely conserved, although the magnitude of each droplet mode changes as infected individuals breathe, speak, sing, laugh, cough, and sneeze. Here we evaluate how each type of respiratory droplet transits through central ventilation systems and the implications thereof for infectivity of COVID-19. We find that while larger oral droplets can transmit through the air handling systems, their size and concentration are greatly reduced with but few oral droplets leaving the source room. In contrast, the smaller droplets that originate from the bronchioles and larynx are much more effective in transiting through the air handling system into connected rooms. This suggests that the ratio of lower respiratory or deep lung infections may increase relative to upper respiratory infections in rooms connected by central air handling systems. Also, increasing the temperature and humidity in the range considered after the droplets have achieved an “equilibrium” size reduces the probability of infection.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• Grant/Contract Number: AC05-76RL01830
• OSTI ID: 1845842
• Report Number(s): PNNL-SA-161825
• Journal Information: International Communications in Heat and Mass Transfer, Journal Name: International Communications in Heat and Mass Transfer Vol. 132; ISSN 0735-1933
• Publisher: ElsevierCopyright Statement
• Country of Publication: United States
• Language: English