Influence of indoor environmental conditions on airborne transmission and lifetime of sneeze droplets in a confined space: a way to reduce COVID-19 spread

Effects of indoor temperature (T(∞)) and relative humidity (RH(∞)) on the airborne transmission of sneeze droplets in a confined space were studied over the T(∞) range of 15–30 °C and RH(∞) of 22–62%. In addition, a theoretical evaporation model was used to estimate the droplet lifetime based on experimental data. The results showed that the body mass index (BMI) of the participants played an important role in the sneezing jet velocity, while the impact of the BMI and gender of participants was insignificant on the size distribution of droplets. At a critical relative humidity RH(∞,crit) of 46%, the sneezing jet velocity and droplet lifetime were roughly independent of T(∞). At RH(∞) < RH(∞,crit), the sneezing jet velocity decreased by increasing T(∞) from 15 to 30 °C, while its trend was reversed at RH(∞) > RH(∞,crit). The maximum spreading distance of aerosols increased by decreasing the RH(∞) and increasing T(∞), while the droplet lifetime increased by decreasing T(∞) at RH(∞) > RH(∞,crit). The mean diameter of aerosolized droplets was less affected by T(∞) than the large droplets at RH(∞) < RH(∞,crit), while the mean diameter and number fraction of aerosols were more influenced by RH(∞) than the T(∞) in the range of 46% ≤ RH(∞) ≤ 62%. In summary, this study suggests suitable indoor environmental conditions by considering the transmission rate and lifetime of respiratory droplets to reduce the spread of COVID-19. GRAPHICAL ABSTRACT: [Image: see text] SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s11356-023-25421-x.