Effect of Infector’s location and occupants’ activity level on airborne spread in a gym – an experimental and CFD study

¹ Department of Mechanical Engineering, School of Engineering, Aalto University, Espoo Finland
² Department of Civil Engineering and Architecture, Tallinn University of Technology, Tallinn, Estonia
³ Department of Civil Engineering, School of Engineering, Aalto University, Espoo, Finland
⁴ Department of HVAC, College of Urban Construction, Nanjing Tech University, Nanjing, China

^* Corresponding author: muhammad.ejaz@aalto.fi

Abstract

The airborne spread of pathogens in indoor environments, such as gyms, has gained significant importance due to its potential role in the transmission of infectious diseases. The presented study was performed in a gym setting equipped with a mixing ventilation system, spanning a floor area of 173.5 m² (17.5m x 9.9m). Using a combination of computational simulations and field measurements, the investigation assessed the effect of source location with respect to exhaust on the distribution of airborne particles. This study also encompassed the effect of pathogens spread on two different levels of physical activities i.e., sedentary, and heavy. The findings were quantified using the local air quality index. The research revealed that when the sedentary contaminant source was positioned near the exhaust, there was a substantial reduction in the spread of contaminants, leading to higher values of the local air quality index, ranging between 0.1 – 5.5 as compared to the value of 0.1-1.2 when the source was farther away from the exhaust. It means when the source is near the return opening, the contaminants could be exhausted before they are fully mixed in the gym environment. For heavy physical activity, when there were increased breathing rates and higher heat gains associated with the occupants, the influence of the source’s location still exists, but there was a significant reduction in the local air quality index as compared to sedentary activity as the value was between 0.1 - 3.2 for the infector near the exhaust. The investigation emphasizes the need to account for physical activity levels when designing gym ventilation systems due to significantly higher contaminant spread during heavy activity. Additionally, the investigation has revealed the effect of injector location, particularly with respect to exhaust grille.