A study conducted at the concert hall Konzerthaus Dortmund in Germany, investigated the spatial dispersion of aerosols and CO2.
It concluded: "Utilization of the existing central ventilation system and the wearing of face masks greatly reduces aerosol and CO2 pollution, to the point that full occupancy of the concert hall would theoretically be conceivable."
The operative word is "theoretically." The study's authors still recommend a checkerboard auditorium layout, which would reduce capacities to around 50%, to ensure that the airflow is still sufficient in the corridors and foyers.
Measurements of aerosol transmission within the concert hall took place on Nov. 2-3, as well as Nov. 20. More detailed findings taken from the study include:
- 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 neighboring 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 neighboring 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 better assess the dispersion of airborne particles in the auditorium.
The study was conducted by the Fraunhofer Heinrich Institute Goslar and the measurement specialists ParteQ on behalf of Konzerthaus Dortmund.
The building's artistic director Dr Raphael von Hoensbroech commented: "Concert halls and theaters are not places of infection. 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 theaters can again admit sufficient audiences when they reopen."
Many professionals Pollstar has been talking to over these past months, including venue operators and concert promoters, have pointed out that 50% capacity wouldn't be enough to run economically viable events.
In summary, the study concludes, "a reopening with at least 50% capacity in a checkerboard arrangement, with one seat free between each seated group, can be recommended on the basis of the study results, especially since the safety distances in the foyer areas and on routes in and out of the auditorium can be ensured.
"A lower occupancy rate would have no added value for infection control. From a hygiene perspective, once the overall infection figures have returned to a low level it would be conceivable to have a fully occupied auditorium at a later date, providing masks are worn. This could be backed up, for example, with model-based calculations."
The findings are relevant to venues of a similar size. The auditorium of Konzerthaus Dortmund, which first opened in autumn 2002, has 1,550 seats.