Analysis of multiple factors influencing the deposition velocity of fine particles onto the body surfaces of healthcare workers

The risk of exposure for healthcare workers (HCWs) during the COVID-19 pandemic has been significantly elevated. In addition to respiratory exposure, HCWs can be exposed to aerosol particles that deposit on the surfaces of their bodies, leading to infection. However, there is a dearth of quantitative analysis of the factors that influence particle deposition onto HCWs. In this study, the deposition velocities of fine particles on a standing manikin were experimentally quantified inside a small-scale chamber under three ventilation modes (top air supply and side air return (TAS), side air supply and side air return (SAS), and underfloor air supply and side air return (UFAS)) and two air change rates (6 and 12 ACH). The effects of multiple factors on the deposition velocity of fine particles onto human surfaces were systematically investigated using numerical modeling. Under different forms of airflow organization, when the particle size increased from 0.1 to 10 μm, the deposition velocity curve exhibited a ‘U’ shape, with the minimum deposition velocity occurring near a particle size of 0.1–0.4 μm. The particle deposition velocity onto the reclining manikin was 1.1–1.9 times the velocity onto the standing manikin. The deposition velocity onto the unheated manikin was 1.1–1.4 times that onto the heated manikin. This study subsequently investigated the deposition exposure on a HCW's body in a full-scale model. Deposition on the upper body and legs accounted for more than 80% of the total body volume, while the whole-body deposition was 2.2 to 6.7 times greater than the inhalation volume.