CFD-Based and Experimental Investigation of Indoor Air Quality: Particulate Matter Dispersion and Exposure in Library Buildings

Indoor air quality (IAQ) is a critical determinant of occupant health, comfort, and cognitive performance, particularly in densely occupied indoor environments such as libraries. This study aims to quantify particulate matter (PM) dispersion dynamics and exposure characteristics through an integrated experimental and computational framework. Three-dimensional CFD simulations were conducted using Flow-3D to resolve the transient transport behavior of multiple PM fractions (PM0.3–PM10) under realistic indoor conditions, and the results were validated against in situ measurements obtained from two library buildings. The findings demonstrate that fine particles (PM0.3–PM1.0) remain suspended at occupant breathing height for extended durations, whereas coarse particles (PM5–PM10) predominantly undergo gravitational settling and accumulate near floor regions. A strong agreement between numerical predictions and experimental data was achieved for PM2.5 and PM10, while discrepancies for ultrafine particles were attributed to turbulence-induced diffusion and Brownian motion. Furthermore, the results highlight the critical role of airflow distribution, ventilation configuration, and spatial obstructions in governing particle transport and the formation of localized high-concentration zones. These findings underscore that ventilation effectiveness is primarily controlled by airflow patterns rather than airflow rate alone. The study confirms that CFD, when supported by experimental validation, provides a robust tool for assessing IAQ and informing ventilation design strategies to mitigate occupant exposure in indoor environments.