Airborne transmission between room occupants during short‐term events: Measurement and evaluation

Abstract

This study experimentally examines and compares the dynamics and short‐term events of airborne cross‐infection in a full‐scale room ventilated by stratum, mixing and displacement air distributions. Two breathing thermal manikins were employed to simulate a standing infected person and a standing exposed person. Four influential factors were examined, including separation distance between manikins, air change per hour, positioning of the two manikinsand air distribution. Tracer gas technique was used to simulate the exhaled droplet nuclei from the infected person and fast tracer gas concentration meters (FCM41) were used to monitor the concentrations. Real‐time and average exposure indices were proposed to evaluate the dynamics of airborne exposure. The time‐averaged exposure index depends on the duration of exposure time and can be considerably different during short‐term events and under steady‐state conditions. The exposure risk during short‐term events may not always decrease with increasing separation distance. It changes over time and may not always increase with time. These findings imply that the control measures formulated on the basis of steady‐state conditions are not necessarily appropriate for short‐term events.

Modelling aerosol transport and virus exposure with numerical simulations in relation to SARS-CoV-2 transmission by inhalation indoors

“…In earlier studies, pathogen transmission has been investigated widely in various indoor environments ( Li et al, 2007 , Morawska et al, 2017 , Ai and Melikov, 2018 ). In many cases, CFD and experimental studies have been conducted to examine the airborne transmission in simplified environments ( Yu et al, 2004 , Zhang and Chen, 2006 , Liu et al, 2017 ) that may have an association with ventilation ( Li et al, 2005 , Olmedo et al, 2012 , Cao et al, 2015 ), airflow interaction ( Bivolarova et al, 2017 , Li et al, 2018a , Ai et al, 2019 ), in hospitals ( Yu et al, 2005 , King et al, 2015 , Cho, 2019 ) and offices ( He et al, 2011 ). Certain studies also consider transport induced by human motion ( Edge et al, 2005 , Han et al, 2014 ) as well as breathing, talking and coughing ( Gupta et al, 2010 , Licina et al, 2015 , Li et al, 2018b ).…”

Quantitative assessment of the risk of airborne transmission of SARS-CoV-2 infection: Prospective and retrospective applications

“…The airborne transmission of a virus and the consequent contagion risk assessment is a complex issue that requires multidisciplinary knowledge. It is necessary to understand the characteristics and mechanisms behind the generation of respiratory microdroplets ( Ai and Melikov, 2018 , Holmgren et al, 2010 ), the survival of viruses in microdroplets ( van Doremalen et al, 2020 ), the transport of microdroplets and human exposure to them ( Ai et al, 2019a ), and the airflow patterns that carry microdroplets in buildings ( Ai et al, 2019b ). Expiratory human activities generate virus-carrying microdroplets that are small enough to remain aloft in air during exhalation, talking, and coughing ( Holmgren et al, 2010 , Morawska et al, 2009 , Morawska and Cao, 2020 ).…”

Evaluation of an innovative pediatric isolation (PI) bed using fluid dynamics simulation and aerosol isolation efficacy

“…Nosocomial infections (NIs), also known as hospital-acquired infections, are mainly caused by airborne pathogens and interpersonal contact in hospitals. It has been reported that the air in hospitals and other health service buildings contains microbial aerosols, and thus controlling the level of pathogenic microbial infections ensures the safety of workers and patient groups (Ai et al 2019;Lanzerstorfer et al 2019). Studies have confirmed that viruses also exist in the air and are very likely to spread via airborne transmission (Guo et al 2020;Ong et al 2020).…”