Effect of ventilation and climatic conditions on COVID-19 transmission through respiratory droplet transport via both airborne and fomite mode inside an elevator

Abstract

A numerical analysis using OpenFOAM has been performed in this work to investigate the infection risk due to droplet dispersal in an enclosed environment resembling an elevator, since infection risk in such confined places is very high. The effect of two scenarios on droplet dispersal, namely, the quiescent and the fan-driven ventilation, both subjected to various climatic conditions (of temperature and humidity) ranging from cold–humid (15 °C, 70% relative humidity) to hot–dry (30 °C, 30% relative humidity) have been studied. A risk factor derived from a dose–response model constructed upon the temporally averaged pathogen quantity existing around the commuter's mouth is used to quantify the risk of infection through airborne mode. It is found that the hot, dry quiescent scenario poses the greatest threat of infection (spatio-averaged risk factor 42%), whereas the cold–humid condition poses the least risk of infection (spatio-averaged risk factor 30%). The proper fan speed is determined for the epidemiologically safe operation of the elevator. The fan ventilation scenario with 1100 RPM (having a spatio-averaged risk factor of 10%) decreases the risk of infection by 67% in a hot, dry climatic condition as compared to a quiescent scenario and significantly in other climatic ambiences as well. The deposition potential of aerosolized droplets in various parts of the respiratory tract, namely, the extrathoracic and the alveolar and bronchial regions, has been analyzed thoroughly because of the concomitant repercussions of infection in various depths of the respiratory region. In addition, the airborne mode of infection and the fomite mode of infection (infection through touch) have also been investigated for both the ventilation scenarios.