Numerical study on aerosol dispersion and infection risk controlling mechanism in an isolation ward with various ventilation strategies

This article numerically studied the aerosol transport and infection risk controlling mechanism in an isolation ward with various ventilation strategies, including up-supplying and down-exhaust (UD), up-supplying and up-exhaust (UU), under floor air distribution (UFAD) and perforated ceiling air supplying (PCAS). The numerical models were first validated by the measurements from the present experiments and the literature. On the basis of a dose-response model, an infection risk evaluation model coupled with CFD was developed. Then, effects of ventilation strategy, air change rate and virus type on the flow structure, aerosol dispersion and infection risk within the wards were then analyzed. Results indicate that streamlines from the two patients’ mouths are flowed directly to outlets in the wards with UU and UFAD, whose heights are relatively higher. Consequently, the isolation ward with UU has the lowest quantity of suspended aerosols and overall infection risk, followed by UFAD, PCAS, and UD. In special, the average and maximal infection risk within the isolation ward is respectively determined by the total quantity and the relative standard deviation of aerosol concentrations. In other words, when optimizing airflow organization within an isolation ward by mechanical ventilating, not only a high removal efficiency but also a high dispersion ability of contaminant or airborne bio-aerosols should be reached simultaneously, so that both of the average and maximal infection risks can be properly controlled.