Review of the assumption of ideal mixed ventilation and estimation of attendances at trade fairs in exhibition halls

¹ Heinz Trox Wissenschafts gGmbH, 52074 Aachen, Germany
² Institute for Energy Efficient Buildings and Indoor Climate, E.ON Energy Research Center, RWTH Aachen University, 52074 Aachen, Germany

^* Corresponding author: tobias.burgholz@htx-wissenschaft.de

Abstract

During the SARS-CoV-2 pandemic, large-scale events were initially suspended categorically without consideration of ventilation technology. In this study, CO₂ concentrations were measured during three trade fairs in the fall of 2021 at Messe Frankfurt with the aim of assessing air mixing and dilution of loads emitted through human respiration. 24 sensors were installed on columns near aisles, in peripheral areas and exhaust/ambient air ducts. At three positions, in addition to a height of 2 m, measurements were taken at 3.2 m height to reveal potential stratification effects. Finally, attendances were estimated based on exhaust/ambient air CO₂ levels and ambient air volume flows. Results show that the maximum CO₂ concentration during visiting hours never exceeded 835 ppm. Indoor air quality thus qualified as hygienically insignificant at all times. Furthermore, no stratification was detected, indicating that air was mixed well without apparent local accumulations of CO₂ and thus potentially infectious aerosols within the breathing zone. Estimated mean attendance corresponds to information provided by Messe Frankfurt. Finally, results indicate that the exhaust CO₂ concentration represents a good indicator to assess air quality within the occupied zone in large-scale halls, making elaborate measurements within the occupied zone obsolete. Further evaluation is needed to support this.