How to quantify and minimize the risk of airborne COVID-19 transmission in football arenas?

In many ways the large inflatable arenas that are commonly used in football are more resembling outdoor conditions than indoor duet to their size, volume, and effective ventilation. However, in Covid-regulations these are considered indoor areas and thus regulations for number of people using these facilities are very tight. Also, football is a contact game where people move and run close to each other, which may increase the risk of COVID-19 transmission from player to other. However, the largest issue currently is that there is no reliable information about the risk of catching COVID-19 in football arenas and thus the games and practices has been mostly cancelled for long time.

In the ACCC Impact Task 4 we decided to study what is the risk of airborne COVID-19 transmission in football arenas and how it could be minimized. This work is done in collaboration with Finnish Meteorological Institute, Tampere University, VTT Technical Research Centre and University of Helsinki. During spring 2021 we visited two football halls, one in Järvenpää (Fig 1) and another in Jakomäki. This collaboration was organized by Jukka Airaksinen (MPS) and Hilppa Gregow (FMI, PK35 T06-08 coach) who were aware of the COVID-19 impact on football coaching and players since the beginning of the pandemic.

Figure 1. Järvenpää football hall

We learned that the regulations for number of people allowed to train in a huge football hall are tight and confusing. We also learned that the ventilation is highly effective and the volume of the football hall is 144 000 m3. To study the air transmission and conditions in the football hall, we made preliminary air flow, temperature and relative humidity measurements using a hot-wire anemometer. The air flows were different depending on location and the distance to ventilation machine. The earlier tests conducted with smoke-generator by the local football club showed that there was also lots of turbulence in air. Based on these we have decided to put low-cost sensors to measure the air quality in the football arena for a year. The sensors monitor PM1, PM2.5, PM10, eCO2, TVOC, concentrations as well as light, noise, and meteorological parameters (T, RH, P) with suitable time resolution and were developed in the iSCAPE project (www.iscapeproject.eu). This way we could detect how much the training increases the CO2, VOC’s, or PM concentrations in air. Prior to measurements we conducted co-location study to ensure the results of sensors are comparable (Fig. 2).

Figure 2. Sensor co-location study setup

The plan is to install the sensors at the football arena and monitor the conditions during a one-year period. The next steps include also a modeling study on Covid transmission based on preliminary measurements and finding further funding for this important topic! We think that it is important to ensure the continuation of practices and games also during future epidemics.

For more information:

Hilppa Gregow: Hilppa.gregow(a)fmi.fi

Hilkka Timonen; Hilkka.timonen(a)fmi.fi

Antti Mäkelä; Antti.makela(a)fmi.fi