On behalf of the Dortmund Konzerthaus, the Fraunhofer Heinrich Hertz Institute in Goslar and the measurement technology company ParteQ have experimentally investigated the spatial spread of aerosols and CO2 in a concert hall. The study was carried out in cooperation with the Federal Environment Agency and hygiene experts. It is the first published study with the aim of obtaining experimental data to assess a possible risk of corona infection when visiting concert halls.

Scientific setting in the Konzerthaus Dortmund (Photo: Simeon Klein)

In November 2020, extensive measurements were made in the auditorium and the foyer of the concert hall. The evaluations of the experimental investigations show that, especially in the hall, under the given conditions, the risk of spreading infections through aerosol transmission can almost be ruled out. Above all, the existing central ventilation system and the wearing of mouth and nose protection reduce the aerosol and CO2 pollution significantly, so that theoretically full occupancy in the hall would be conceivable.

However, taking into account the access routes and foyers, it is recommended that the hall be occupied in a chessboard pattern and thus 50% of the hall capacity. In addition to concrete results for a visit to the Dortmund Concert Hall, the study can also provide information for other concert halls or theaters of a similar size.

Study by the Fraunhofer Heinrich Hertz Institute provides an important basis for reopening

“Concert halls and theaters are not places of infection,” Dr. Raphael von Hoensbroech, director of the Konzerthaus Dortmund, said this in September. However, the present study does not serve to criticize previous decisions: “The past few months have shown that politics needs scientifically sound decision-making bases. With our study we want to contribute to the fact that the concert halls and theaters can again admit sufficient audience when they open. “

The relevance of the study is also confirmed by NRW Minister of Culture and Science Isabel Pfeiffer-Poensgen: “The issue of ventilation is a decisive factor for the reopening of cultural institutions. The study by the Dortmund Concert Hall is therefore a valuable component in the effort to enable games to be played even in times of pandemic. At the same time, it shows the great sense of responsibility with which the cultural institutions act towards the public. With a view to the great relevance of ventilation, the state government has set up a joint working group with representatives from cultural institutions, among others, which is currently developing a differentiated opening strategy based on scientific findings. Part of this is a broad-based analysis of the effectiveness of ventilation systems in North Rhine-Westphalian cultural institutions, the implementation of which began at the end of last year. “And she continues:” It is painful that the still high number of infections does not currently allow reopening. It is all the more important to create perspectives and planning security for the time after the lockdown. “

The study provides results that are important for a reopening. The existing measures to contain the corona pandemic are aimed at a general reduction in contacts and thus also mean the closure of the theaters and concert halls to the public. According to the new version of the Infection Protection Act of November 2020, the importance of artistic freedom must be taken into account in the event of restrictions on the operation of cultural institutions or cultural events. As soon as this is possible in view of the infection situation, the cultural institutions should therefore be able to reopen, based on scientific facts and a differentiated view of the respective local and conceptual conditions.

For the Konzerthaus Dortmund, the study results can be used to summarize the following:

• With a mask and with a sufficiently dimensioned fresh air supply via the existing air conditioning system (RLT system), there was practically no influence from test aerosols on any of the neighboring places of an emitting test subject.

• Already the large room volume ensures a strong dilution of contaminated aerosols, due to the supply and exhaust air operation of the air conditioning system without circulating air function, aerosols are effectively transported away in all areas and cannot accumulate.

• Without a mask, you should always keep the direct front seat free, with the remaining neighboring seats an infection is very unlikely based on the examinations. A chessboard occupation of the hall without a mask after taking the seat is recommended in any case.

• Occupying the concert hall with many people does not disturb the air exchange upwards, but rather promotes it through additional thermal effects.

• It is fundamentally necessary to wear masks in corridors, in the break area and in the foyers, since the ventilation works differently here than in the concert hall (e.g. air escapes from the ceiling) and close contacts cannot be ruled out. In addition, all doors to the concert hall remain open during the breaks to allow additional cross-flow ventilation.

• The concert hall cannot trigger a superspreading event with an existing ventilation concept (complete air exchange with outside air every 20 minutes).

• CO2 measurements during operation can help to better assess the spread of airborne particles in the hall.

These results were created in close cooperation with the Federal Environment Agency. »Excellent study with a lot of informative value! That is exactly what we need in terms of information, ”emphasizes Dr.-Ing. Heinz-Jörn Moriske, director and professor at the Federal Environment Agency (Head of the Environmental Hygiene Advisory Center, FB II (BU), Management of the Indoor Air Hygiene Commission), and continues: »I fully agree with the conclusion. With a chessboard-like distribution of the guests and 100% full load of the ventilation system, the risk of infection is very low. Wearing mouth and nose protection in the hall is an advantage, if not as important as previously assumed. ”The hygiene expert Professor Dr. Martin Exner emphasizes the importance of these results: “The study provides an important basis for assessing the risk of transmission of SARS-CoV-2 at concerts with an audience.”

In summary, a reopening with at least 50% of the capacity as a chessboard with one vacant seat between the seating groups can be recommended on the basis of the study results, especially since the safety clearances in the foyer areas and the paths in and out of the hall can be ensured. A lower utilization would therefore have no added value for infection protection. If the overall number of infections is again at a low level, from a hygienic point of view, when wearing mouth and nose protection, a fully occupied hall might later be conceivable. This could e.g. be secured via model-based calculations.

In addition to concrete results for a visit to the Dortmund Concert Hall, the study can also provide statements for other concert halls or theaters in which there are comparable framework conditions in certain points. The Fraunhofer Heinrich Hertz Institute can carry out additional studies with relatively little effort on houses that do not meet these requirements. The head of the study is Prof. Dr. Wolfgang Schade, Head of the Fiber Optic Sensor Systems Department at the Fraunhofer Heinrich Hertz Institute.

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