Distribution Characteristics of Respiratory Aerosols in Enclosed Environments

Dispersion characteristics of respiratory droplets in indoor environments are important in controlling transmission of airborne diseases indoors. This study investigates the spatial concentration distribution and temporal evolution of exhaled and sneezed/coughed droplets within the range of 1.0 similar to 10.0 mu m in an office room with three air distribution methods, specifically mixing ventilation (MV), displacement ventilation (DV), and under-floor air distribution (UFAD). The simulation results indicate that exhaled droplets with diameters up to 10.0 mu m from normal respiration process are uniformly distributed in MV. However, they become trapped in the breathing height by thermal stratifications in DV and UFAD, resulting in a high droplet concentration and an increased exposure risk to other occupants. Sneezed/coughed droplets are more slowly diluted in DV/UFAD than in MV. Low air speed in the breathing zone in DV/UFAD can lead to prolonged human exposure to droplets in the breathing zone.