Fluorescent Aerosol Particles in Outdoor and Mechanically Ventilated Indoor Air in a Subtropical Urban Environment

This study characterized fluorescent aerosol particles (FAPs) in seven mechanically ventilated commercial buildings in Hong Kong using two laser-induced fluorescence instruments to understand bioaerosol spatiotemporal dynamics. Simultaneous indoor and outdoor measurements revealed that the indoor FAP fraction of total particles was significantly higher than outdoors, with fungi-like FAPs dominating both environments. Diurnal trends indicated that human activity strongly influenced FAP concentrations, particularly increasing coarse-mode particles (> 2 µm) and pollen-like FAP ratios during daylight hours. While indoor FAP variations were primarily driven by particulate matter and meteorological factors (e.g., humidity), outdoor variations correlated with anthropogenic tracers like total volatile organic compounds. These findings underscore the impact of occupancy and ventilation on bioaerosol concentrations, providing critical insights for optimizing indoor air quality and mitigating bioaerosol exposure.