Occupancy and Air Quality Model for Outdoor Events: A Strategy for Preventing Disease Transmission at Mass Events

Abstract

This paper proposes a novel model to determine occupancy density for outdoor events to prevent infectious disease transmission caused by the impossibility of proper dilution of human effluents in the atmosphere. It uses standardization processes to calculate natural ventilation air renewal and establishes theoretical occupancy based on activity and exhaled air percentage, aiming for indoor air quality comparable to the IDA2 standards. The study focuses on mass events in Mostoles (Spain), analyzing street activities and bullring events. It found that above a certain height in the open air, infection risk is low, eliminating capacity limitations. The resulting mathematical expressions can be adapted to different pathogens, ensuring the quality of indoor air conditions through capacity control. The process determines the ventilation required based on physical activity, considering both unrestricted and restricted situations. The relationship between required and available ventilation prevents disease transmission. The method’s effectiveness is demonstrated through comparisons between estimates and environmental measurements during Mostoles events. The maximum outdoor occupancy at ground level to achieve air quality comparable to the IDA2 standards is determined to be 2.36 persons/m2, while to prevent the transmission of SARS-CoV-2 it is determined to be 1.98 persons/m2. In addition, transmission will not occur during mass gatherings in locations over five meters above ground level. In conclusion, this model provides an adaptable tool to prevent the spread of infectious diseases at outdoor events by ensuring adequate air quality through occupancy control. © 2025 by the authors.