A scientific study into the distribution of airborne particles, which took place at the 1,500-seat Konzerthaus in Dortmund, has revealed there is little risk of infection in properly ventilated concert venues.

The study was conducted over three days in November by the Fraunhofer Heinrich Hertz Institute, and measurement specialists ParteQ, in collaboration with the German Environment Agency.

A high-tech dummy (pictured) was used to investigate the spatial dispersion of aerosol and CO2, and the results showed that providing the venue is ventilated and attendees are wearing face masks, the risk of transmission “can almost be excluded, especially in the auditorium.”

The study found that using the venue’s existing ventilation system, along with the wearing of face masks, reduced the risk of airborne transmission to the point that full occupancy of the concert hall would “theoretically be conceivable”. However the study recommended a checkerboard auditorium layout with one seat free between each seated group, enabling a 50% venue capacity.

Konzerthaus Dortmund artistic director Dr Raphael von Hoensbroech said, “The past months have shown that politicians need a scientifically sound basis for decision making. With our study, we want to contribute, to help ensure that concert halls and theatres can again admit sufficient audiences when they reopen.”

North Rhine-Westphalia minister of culture and science Isabel Pfeiffer Poensgen said, “The issue of ventilation is a decisive factor for the reopening of cultural institutions. The study of Konzerthaus Dortmund is therefore a valuable building block in the effort to enable performances to continue, even in times of pandemic. At the same time, it shows the great sense of responsibility that cultural institutions have towards their audiences. In view of the great relevance of ventilation, the state government has set up a joint working group with cultural institution representatives who, among others, are currently developing a differentiated opening strategy based on scientific findings.”

Dr Heinz-Jörn Moriske, director and professor at the Federal Environment Agency, said the study was “excellent with a lot of significance”. He added, “I can fully endorse the conclusion. With a checkerboard distribution of guests and 100% full load of the indoor air system, the risk of infection is very low. Wearing mouth-nose protection in the auditorium is advantageous, although not as important as previously assumed.”

A summary of the report’s findings:

  • With a mask, and with a sufficient supply of fresh air via the existing ventilation and air conditioning system, there was practically no influence of test aerosols on any of the neighbouring places from an emitting test person during the tests.
  • The large room volume already ensures a strong dilution of contaminated aerosols, and due to the supply and extraction air operation of the ventilation system without recirculation function, aerosols are effectively removed in all areas and cannot accumulate.
  • Without a mask, the seat directly in front should be kept free. With the remaining neighbouring seats, infection is very unlikely. A checkerboard seating arrangement of the auditorium is recommended in any case.
  • Greater number of people in the auditorium does not disturb the upwards air flow, but rather promotes it through additional thermal effects.
  • Wearing masks is always necessary in corridors, in break areas, and in the foyers, as the ventilation system works differently here than in the auditorium (where air escapes through the ceiling) and where close contact cannot be ruled out. During breaks all doors to the auditorium should remain open to allow for additional crossflow ventilation.
  • The concert hall cannot trigger a superspreading event with the existing ventilation in place (with a complete air exchange with fresh, outside air, every 20 minutes).
  • CO2 measurements during operation can help to better assess the dispersion of airborne particles in the auditorium.