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Air exchange rates and advection–diffusion of CO 2 and aerosols in a route bus for evaluation of infection risk
Author(s) -
Shinohara Naohide,
Tatsu Koichi,
Kagi Naoki,
Kim Hoon,
Sakaguchi Jun,
Ogura Isamu,
Murashima Yoshiko,
Sakurai Hiromu,
Naito Wataru
Publication year - 2022
Publication title -
indoor air
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.387
H-Index - 99
eISSN - 1600-0668
pISSN - 0905-6947
DOI - 10.1111/ina.13019
Subject(s) - ventilation (architecture) , diffusion , open air , environmental science , advection , open source , meteorology , engineering , physics , operating system , computer science , thermodynamics , architectural engineering , software
Abstract As COVID‐19 continues to spread, infection risk on public transport is concerning. Air exchange rates (ACH) and advection–diffusion of CO 2 and particles were determined in a route bus to evaluate the infection risk. ACH increased with bus speed whether windows were open or closed, and ACH were greater when more windows were open. With two open windows, ACH was greater when a front and rear window were open than when two rear windows were open. With both front and rear ventilation fans set to exhaust, ACH was more than double that when both were set to supply. With air conditioning (AC) off, CO 2 and particles spread proportionally at the same rate from a source, whereas with the AC on, the spread rate of particles was about half that of CO 2 , because particles might be trapped by a prefilter on the AC unit. Infection risk can be reduced by equipping AC unit with an appropriate filter. Calculations with a modified Wells–Riley equation showed that average infection risk was reduced by 92% in the moving bus with windows open comparing to with windows closed. When the bus was moving with windows closed, exhaust fan operation reduced the average risk by 35%.