Second German study shows venues “not places of infection”

A second study in Germany of the movement of airborne particles in an indoor environment has shown there is a negligible risk of infection in properly ventilated concert venues.

The scientific study, which took place at Dortmund’s 1,500-seat Konzerthaus, was carried out over three days in November by the Fraunhofer Heinrich Hertz Institute of Goslar and particle measurement company Parte Q, with the backing of Germany’s Federal Environment Agency. It follows August’s Restart-19 study by the University Hospital of Halle, the results of which were published in October, which concluded that, with adequate ventilation, live events posed a “low to very low” risk of person-to-person transmission.

Unlike Restart-19, which featured only human participants, the Dortmund study used a high-tech dummy, dubbed Oleg, to simulate human breathing in the Konzerthaus.

For the study, on 2–3 and 20 November, the team measured aerosol transmission across the venue, including in the auditorium and foyer. Their conclusion is that under certain conditions – that the venue has a sufficient fresh-air supply and all attendees are wearing face masks – the risk of someone infecting healthy concertgoers with Covid-19 “through aerosol transmission can be almost ruled out”, according to a Konzerthaus release.

“This is exactly what we need in terms of information”

“Concert halls and theatres are not places of infection,” says Dr Raphael von Hoensbroech, director of Konzerthaus Dortmund. “The past few months have shown that politics needs a scientifically sound basis for decision-making. With our study, we want to ensure that concert halls and theatres may again admit sufficient audiences when they reopen.”

The key findings of the study include:

• With masks and a sufficient fresh air supply via the Konzerthaus’s existing air conditioning system – a so-called RLT (Raumlufttechnik), or room ventilation system – there was practically no influence of the test aerosols on all nearby surfaces
• The large size of the room already ensures a strong dilution of contaminated aerosols, and the air conditioning effectively removes all aerosols, never allowing them to accumulate
• A full concert hall does not interfere with the passage of air upwards, but rather promotes it through additional thermal effects
• It is necessary to wear masks in corridors, rest areas and the foyers, as the ventilation there (in Konzerthaus Dortmund’s case) works differently to in the concert hall itself and close contact cannot be ruled out
• The Konzerthaus cannot trigger a superspreading event with its existing ventilation system, which completely replaces the air inside the venue with external air every 20 minutes
• Measuring CO2 during an event can help to better assess the spread of airborne particles in the hall

While in theory the Konzerthaus should be able to operate at full capacity without risk, in practice (taking into account the difficulties of socially distancing in corridors, bars, etc.) a so-called chequerboard seating system, with every other seat occupied, is recommended by the scientists. Either way, when a patron is unable to wear the mask, the seat directly in front of them should be kept free.

“Concert halls and theatres are not places of infection”

While the study only provides concrete results for transmission in Konzerthaus Dortmund, the Fraunhofer Heinrich Hertz Institute is able to apply the results to other similar concert halls and venues, it says. Even for those which don’t meet the requirements, additional studies can be carried out with “relatively little effort”, according to the head of the study, Wolfgang Schade.

Heinz-Jörn Moriske, director of the Federal Environment Agency, describes the Dortmund experiment as an “outstanding study with a lot of informative value”, adding: “This is exactly what we need in terms of information. With a chessboard-like distribution of guests and the ventilation system at 100%, the risk of infection is very low.”

Additionally, he says, “the wearing of mouth and nose protection in the hall is advantageous, even if not as important as previously assumed.”

“This study provides an important basis for assessing the risk of transmission of Sars CoV-2 at concerts with an audience,” agrees hygiene expert Martin Exner.

This article forms part of IQ’s Covid-19 resource centre – a knowledge hub of essential guidance and updating resources for uncertain times.

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