Analytical Model for Indoor Decay of Airborne Particles

The dispersion of pathogen-laden particles in indoor environments depends on several factors, including room size, airflow strength, temperature, humidity, and the physical properties of expelled droplets and aerosols. Accurately predicting such a phenomenon remains an open challenge. In this presentation, we propose and validate an analytical formulation describing the temporal decay dependence of room-average particle concentration under a range of ambient conditions, including room size, the strength of air circulation, turbulence integral length scales, and particle size distributions. Large-eddy simulations of polydisperse droplets and aerosols are conducted in a horizontally-periodic environment, where air circulation is forced to generate homogeneous isotropic turbulence in the bulk of the flow. An analytical solution is derived for an average room concentration as a function of time, accounting for nuanced variability of flow and ambient room conditions. Model predictions compare well against the numerical data, showcasing the potential of the proposed formulation. The model is tailored for use within agent-based epidemiological modeling frameworks. This study contributes to our understanding of airborne disease transmission in indoor environments and proposes a foundation for improved risk assessment and mitigation strategies.