Experimental analysis of the ventilation rate in an amphitheater operating under the COVID-19 pandemic constraints

Abstract

In the context of the Covid-19 pandemic (officially declared by the WHO on March 11th, 2020), indoor air quality (IAQ) has resurged as a renewed paradigm, demanding enhanced attention, especially in spaces with high occupancy density, as is the case of school buildings. To minimize the risk of contamination indoors, it is needed to assure low concentrations of the biological pollutant load eventually resulting from the exhalation of the microorganism SARSCOV- 2, through the dilution capacity of the ventilation systems. One way of checking the risk reduction is through the spatially comprehensive assessment of the air exchange rate (AER) in the indoor space. The present study was motivated by a request from the Faculty of Sciences and Technology of the University of Coimbra (FCTUC) in Portugal, whose spaces have been used under restrictive conditions derived from the recommendations on the operation of buildings during the pandemic. Two onsite experiments were carried out in an Amphitheater with only the exhaust component on, due to technical issues with the HVAC system in that period. The tests comprised measurements in ten different locations for representative monitoring of the occupied zone of the space. The estimation of the AER in the amphitheater in both tests was based on the analysis of the time evolution of the tracer gas (CO2) concentration measured by each sensor/equipment. The results showed that the analyzed space presented an adequate rate of air renewal to ensure an effective dilution of indoor pollutants, and likewise of the biological pollutant load possibly resulting from the exhalation of microorganisms by an infected occupant.