The ILK has been ordered by the city of Dresden (unit for education and youth) to scientifically supervise the testing of air filtering constructions for day cares and schools.
At the 144th primary school, Dipl.-Ing. Christian Friebe’s team tested different versions of secondary air cleaning devices in specific room situations and during the regular teaching process. The data measured was assessed based on the FGK status report 52. The goal was to provide a reliable data base for the City of Dresden to which it may adjust its further way of proceeding. The following measurement parameters have been considered and captured: room and building information, number of people, device information, air volume flow, CO2 concentration, sound pressure level, particle concentration in the room and sampling in order to determine the concentration of Covid19. In order to be able to compare and assess, the same measurands have been gathered WITHOUT the use of a circulating air cleaner.
The conclusion of the ILK scientists:
Secondary air cleaning devices are a quickly available and flexible solution for retrofitting to clean the air from particles such as viruses etc. What is crucial for risk minimization is the clean air delivery rate (CADR). CADR stands for the effectiveness of an air cleaning device based on the room size and the volume of clean air produced per minute. However, secondary air cleaning devices do not provide outside air volume flow and therefore do not contribute to the reduction of CO2 or a change of air that would be hygienically necessary. A solution in the short run is to intensify window ventilation. However, this solution reaches its limits quickly due to air draft, thermal comfort, energy consumption and outside noise. A sustainable solution can only be reached by means of mechanical ventilation systems. Further information can be found in the leaflet „Lüftung für Bildungsstätten“ (“Ventilation for Educational Institutions”) published by the Association for Building-Climate, which can downloaded from www.fgk.de.