Spatial variability of indoor particle dynamics induced by the human thermal plume

The human body influences indoor particle transport through the generation of a buoyancy-driven thermal plume that modifies near-body airflow and particle dynamics. This study experimentally investigated the influence of the thermal plume on particle transport and apparent removal using a full-scale female thermal manikin (MONICA) instrumented with particulate matter sensors. Experiments were conducted in a 40 m3 controlled chamber (IRINA) under both well-mixed and non-mixed initial conditions, combining a size-resolved reference instrument with a distributed sensor network positioned on and around the manikin. At the chamber scale, size-resolved deposition loss coefficients derived from the reference instrument showed only minor differences between heated and unheated conditions, indicating a limited influence of the thermal plume on room-averaged deposition rates. In contrast, spatially resolved measurements revealed substantial local increases in apparent particle removal, particularly above the manikin, with enhancements reaching 25%. Transient experiments further showed that heating reduced particle detection times in the near-body region by 35–50%, while far-field measurements remained largely unaffected. Complementary CFD simulations were performed to visualise the flow field surrounding the manikin and support interpretation of the observed transport behaviour. Overall, the results demonstrate that the human thermal plume has a limited effect on bulk room deposition but significantly alters near-body particle transport dynamics. These findings highlight the importance of accounting for occupant-generated airflow in indoor aerosol transport, exposure assessment, and ventilation design, particularly in weakly mixed indoor environments.