A Meta-Analysis of Air Change Rate and SARS-CoV-2 Exposure in Residences and Healthcare Facilities

YUETONG ZHANG, Sripriya Nannu Shankar, William Vass, Z. Hugh Fan, John Lednicky, Duzgun Agdas, Chang-Yu Wu, University of Florida

     Abstract Number: 659
     Working Group: Aerosol Science of Infectious Diseases: Lessons and Open Questions on Models, Transmission and Mitigation

Abstract
As SARS-CoV-2 swept across the globe, increased ventilation and implementation of air cleaning were emphasized by the US CDC and WHO as important measures to reduce the risk of inhalation exposure to the virus. To assess whether higher ventilation and air cleaning rates lead to lower exposure risk to SARS-CoV-2, a comprehensive literature review of 1274 studies published between April 2020 and September 2022 were screened for relevancy. Among them, 93 field sampling studies that took place in residences and hospitals were selected, and associated data were compiled. Two metrics were used to assess exposure risk: (1) the concentration of SARS-CoV-2 in air samples and (2) the percentage of air samples in which SARS-CoV-2 was detected. Locations were categorized by type (hospital or residence) as well as by proximity to the sampling location housing the isolated/quarantined patient (primary or secondary). The positivity rates for primary and secondary sites were computed, and subsequently, the outcomes were grouped based on the air changes per hour (ACH) of the primary locations. The ACH were higher in hospitals (mode = 6) compared to residences (mode < 1), and the mean virus concentration in hospital settings (281 copies/L of air) was lower than that in residences (3.96×10⁷ copies/L of air). The mean positivity rate in air samples collected in hospital settings (17.7%) was lower compared to that in residential settings (39.8%). In residences, positivity rates and concentrations were found at similar levels whether in primary or in secondary rooms, which may be explained by the low ACH. Our analyses show that on average SARS-CoV-2 may be present in greater concentrations in residential spaces than in hospital rooms, supporting the notion that a higher air change rate can reduce potential exposure risks to the virus in ambient air.