ESTIMATION OF EXPOSURE LEVELS OF VIRUS – LADEN EXPIRATORY AEROSALS IN A HOSPITAL WARD UNDER IMPERFECT MIXING CONDITION

This study investigated the feasibility of using the spatial distribution of expiratory aerosols and thepercentage viability of airborne viruses to estimate the spatial exposure levels of airborne viruses inrooms under imperfectly mixed condition. Experiments were conducted in a hospital ward withceiling-mixing type ventilation system. A broth solution with a known concentration of bacteriophages,as to simulate airborne viruses, was aerosolized with a droplet size distribution similar to humanexpiratories. Spatial distributions of these aerosols were measured using an aerosol spectrometer. Thepercentage viability of bacteriophages was obtained using in-situ biological air sampling by anAndersen sampler. The applicability of the proposed method was verified by comparing the estimatedexposure levels with those measured directly by in-situ biological air sampling at selected locations.Reasonable agreement was found between the two sets of results. The proposed method was thenused to estimate the exposure levels of patients and hospital workers in the ward. Estimated exposurelevels were found to have significant spatial variations. The proposed method may be further developedinto applications for analyzing airborne infection risk in imperfectly mixed indoor environments and theresults would provide information for establishing working standards in hospitals for virus inducedairborne disease prevention.