Marcel Philipp, the Mayor of the City of Aachen, opened the panel discussion with a special welcome. He did so in German language before the panel speakers switched to English. In the course of the evening, various aspects of aerosols in the context of Covid-19 were discussed in detail. Specific attention was paid to key points such as the transport and dispersion of aerosol droplets, the efficiency of different filtering face pieces and community masks, the role of indoor spaces, and implications of stay-at-home orders on ambient air quality. The panel also emphasized that the aerosol research community has much experience with aerosols and can therefore make an important contribution to understanding and dealing with this pandemic, jointly with medical doctors, epidemiologists and policy makers.
The event was open to the public but due to the regulations of the local Corona Protection Ordinance, only 40 guests joined the panel and the technicians on-site that evening. In addition, the discussion was streamed live on the internet for an international audience. Social distancing in the 45 meters long and 18.5 meters wide Coronation Hall with a very high ceiling was observed and all chairs were spaced well over 6 feet apart. The panelists could not speak with their masks on as unfortunately the acoustics of this ancient hall was very poor with so few people present.
In addition, Dominik Groth from TSI carried out CO2 measurements with a Q-Trak 7575 in the Coronation Hall from start to finish. In a room that is well-ventilated with outside air, virus containing droplets and particles are diluted. Therefore CO2 can serve as a proxy to determine when indoor air gets stale and a room needs ventilation. He first measured the ambient air outside Aachen Town Hall, which delivered the lowest value of the measurement series with 391 ppm of CO2. Once inside he observed an average value of 515 ppm CO2 before the start of the event and then kept moving around inside. At the end of the panel discussion, the CO2 concentration was still between 540 and max. 574 ppm, so the Coronation Hall only saw a moderate increase in CO2 during the event.