Enhancement effect of human movement on the high risk range of viral aerosols exhaled by a sitting person

Abstract

Human movement could affect viral aerosol transmission. We carried out full-scale experiments to study the effect of human movement on viral aerosols exhaled by a sitting thermal breathing manikin (STBM), and describe the indoor airflow characteristic. In static scenarios, the aerosol concentration decreased rapidly beyond 1.5 m from a source person. But when a moving manikin (MM) moved in the same direction as STBM's exhalation, forward high risk range Rf extended from 1.5 m to 3.0 m, and lateral range Rl increased from 1.3 m to 2.0 m, referred to as the enhancement effect. Changes in airflow and pressure, air mixing, and the following of aerosols to movement-induced airflow might explain this effect. The airflow velocity v increased when MM passed at 1 m/s, closely related to distance. At the distance 0.25, 0.55 and 1.05 m to MM, v could be up to 0.64, 0.37 and 0.25 m/s, with average value of 0.27 (±0.088), 0.14 (±0.047) and 0.06(±0.039) m/s, respectively. The air continued flowing after MM stopped for more than 30–60 s. Effects related to exhalation direction and ventilation were compared, indicating that the mechanisms of driving lateral and forward transmission might be different. It would be recommended to reduce cross-area walking in areas with epidemic. The increase in ventilation might limit the enhancement effect.