KKL: Aerosol study provides basis for further opening steps

The study shows that the airflow in the concert hall largely meets expectations and that airborne contaminants are effectively dissipated in the audience area. The results also confirm that the risk of infection can be significantly minimized with consistent protective measures and that safe conditions can be created for visitors in the concert hall. These encouraging results, writes the KKL Luzern, would provide a very good scientific basis for the planned gradual opening steps over the next few months.

Together with its partners Lucerne Festival and Lucerne Symphony Orchestra, the KKL Luzern had commissioned the Lucerne University of Applied Sciences and Arts and the Swiss Center for Occupational and Environmental Health SCOEH to investigate the risk of virus transmission in the concert hall from a ventilation perspective. The aim of the study was to provide a sound scientific basis for the discussion on the upcoming opening steps for the event industry. The concert hall of the KKL Luzern is equipped with a special ventilation system in which the supply air is fed in under the seats in the audience area. This is intended to remove the aerosols emitted by the visitors and other air pollutants more effectively than with pure mixed ventilation.

The measurements were carried out at the end of April in the presence of musicians* and audience (more than 80 people in total) under realistic conditions. The ventilation effectiveness was investigated on the one hand with trace gases and on the other hand with a test aerosol in different areas of the hall, taking into account the ventilation and the activity of the room users (emitter and exposed person). The aerosols used were similar in size to those released by people breathing and speaking.

The study shows that air pollution in the public area is removed much more effectively than with purely mixed ventilation. Together with the generous design of the ventilation system and the large room volume, this results in a risk of infection that can be classified as low for the most part if the protection concept is adhered to. Only wind players and singers pose a slightly increased risk for other musicians singing or playing wind instruments without masks and for the front row of the stalls. Simple protective masks with a retention efficiency of 25 percent were used as the basis for the study. With a certified mask (75 percent) or an FFP2 mask (95 percent), the residual risk can be significantly reduced.

The results of the study are shared with the authorities and interested groups in the sense of an exchange of experiences. They have been incorporated into the test concert with over 500 guests of the Lucerne Symphony Orchestra, which was successfully held on Thursday with the highest level of safety for guests and musicians*. The results would form an important basis for the staging of Lucerne Festival from August 10 to September 12, 2021, the further opening steps of the KKL Luzern as well as the season start of the Lucerne Symphony Orchestra with its new chief conductor Michael Sanderling on October 20, 2021, the KKL writes in the statement.

For the staging of the Summer Festival, the Lucerne Festival has consciously decided to rely on a seating arrangement with safety distances in addition to the mask requirement, thus minimizing the risk of infection. The KKL Luzern uses the study as a basis to enable further facilitations for all concert organizers from July on, under constant compliance with the respective valid conditions, and to return step by step to normal operations.

The study also provides important information for the safe operation of large event venues in times of a pandemic, according to the KKL. The chosen measurement procedure can also be applied to other event venues in Switzerland with similar technical characteristics, so that they can be quickly and efficiently examined by experts.