Abstract：

This study adopts the large eddy simulation (LES) method, focusing on high-frequency respiratory activities, to systematically investigate transient inhalation exposure characteristics and influencing mechanisms by resolving infectious respiratory particles (IRPs) transport trajectories under turbulent fluctuations and susceptible individuals’ inhalation exposure outcomes. The results show that at close distances (0.5 m), susceptible individuals’ transient inhalation exposure exhibits intermittent and fluctuating characteristics, with over 30% of inhalation phases showing no inhalation occurrence, where abnormal exposure values accounting for less than 10% of the exposure process contribute up to 55.88% to cumulative exposure risk. The differences in vortex structures within exhaled airflow under turbulent fluctuations are the key factor causing transient exposure fluctuations. During close-range exposure events, there exist periods when IRPs concentrate in the susceptible individuals’ breathing zones, with higher coupling degree between these periods and inhalation phases leading to stronger exposure fluctuations. Ignoring the impact of transient exposure fluctuations may render existing prevention and control measures ineffective during peak-driven transmission events. In the future, a classified prevention and control system grounded in viral characteristics should be further established.

Keywords:infectious respiratory particle; transient inhalation exposure; turbulent fluctuation; large eddy simulation; respiratory activity; virus prevention and control