Air quality in an air ventilated fitness center reopening for pilot study during COVID-19 pandemic lockdown

Abstract

During COVID-19 lockdowns less people were able to fulfill the WHO recommendations on physical activity. Also, fitness centers were associated to SARS-CoV-2 superspreader events. However, the risk of infection can be strongly reduced by outdoor air ventilation. To investigate whether a reopening of fitness centers can be justified, CO2 concentration was measured during four days in a fitness center.Except for one room, the observed CO2 concentrations were mainly under 800 ppm, which stands for high air quality. The strong decrease of CO2 concentration during the 15 min evacuations following each hour of workout, speaks for the functionality of the ventilation system. In particular, the number of people present in the studio has a strong impact on the estimated CO2 value. In a linear mixed model, an additional CO2 concentration of 2.24 ppm (95 % confidence interval [2.04, 2.43]) was estimated for this setting with a total volume of 4065 m3 in the fitness center and a possible air change rate per hour up to 10. This means, that for 45 visitors, 100 ppm can be added to the predicted concentration.To summarize, a combination of ventilation, restriction of the number of visitors and surveying the CO2 concentration allowing for further restrictions in case of need, seems to be an adequate means to reduce the risk of SARS-CoV-2 infection in fitness centers.