An experimental study on the characteristics of human respiratory aerosol emission in different activity intensity states

Abstract

The COVID-19 pandemic has significantly affected global health and necessitated an enhanced grasp of respiratory infectious disease spread. This research experimentally measured the intensity of exhaled particles with a diameter ranging 0.3–25 μm, emitted by individuals engaging in various activity levels. A total of 58 subjects participated in the experiment, engaging in activities at intensities of 0 km/h, 3 km/h, 5 km/h, 7 km/h, and 10 km/h, respectively. The number of exhaled particles with a diameter of 0.3–0.5 μm accounted for 87% of the total, but their mass accounted for only 11%. Particles larger than 3 μm made up only 1% of the overall mass, while particles between 5 and 10 μm in diameter accounted for 45% of the total mass. The experimental results demonstrated that there was no statistically significant difference in the strength of particles produced by individuals based on gender or activity intensity. The maximum number of particles in the 0.3–0.5 μm range was observed at 7 km/h, reaching 5,226,550 part/min, while the minimum occurred at 3 km/h with 1,161,810 part/min. The differences in the intensity of particles released between individuals could reach two to three orders of magnitude. This study reveals the relationship between exhaled aerosol intensity and activity intensity. It aids public health professionals and engineers in assessing pathogenic aerosols, informing efficient ventilation design to reduce indoor transmission risks.