Human exposure to air contaminants under the far-UVC system operation in an office: Effects of lamp position and ventilation condition

Abstract

The far-UVC (222 nm) system has emerged as a solution for controlling airborne transmission, yet its effect on indoor air quality concerning positioning remains understudied. In this study, we examined the impact of far-UVC lamp position on the disinfection and secondary contaminant formation in a small office. We employed a three-dimensional computational fluid dynamics (CFD) model to integrate UV intensity fields formed by different lamp positions (ceiling-mounted, wall-mounted, and stand-alone types) with the air quality model. Our findings reveal that the ceiling-mounted type reduces human exposure to airborne pathogens by up to 80%. For all the lamp positions, the O₃ concentration in the breathing zone increases by 4–6 ppb after one hour of operation. However, the stand-alone type poses a risk of exposing occupants to elevated levels of O₃, as it creates a high concentration zone (> 25 ppb) near the lamp. Moreover, ventilation plays a crucial role in determining human exposure to airborne pathogens and secondary contaminants. Increasing the ventilation rate from 0.7 h^− 1 to 4 h^− 1 reduces airborne pathogen and secondary contaminant concentrations by up to 90%. However, caution is warranted as it could also lead to elevated O₃ indoors, particularly in high outdoor O₃ conditions.