The issue of air filters is one of the hottest topics of debate in the pandemic. Emotions run particularly high in schools, day-care centers and children. In some places a lot has been invested, in others not. An air filter is not just an air filter.
The following dialogue is typical of the debate: «What do the air filters for classrooms actually do? My child is freezing,” wrote Twitter users “kohondterfay” a few days ago.
The President of the Conference of Ministers of Education (KMK) Karin Prien (CDU) replied: “And that’s exactly where the problem lies: did someone actually tell you that air filters replace ventilation?”
Prien, the Schleswig-Holstein Minister of Education and this year’s KMK President, and her colleagues in the federal states repeatedly emphasize that there should be no more major school closures. In the political debate, however, they are then accused of not having made schools safe enough for continuous face-to-face teaching. A recurring accusation: there are no air filters.
Allegation of “contamination”
Student representatives recently accused politicians of a “contagion plan” with an open letter of complaint online under #WirWerdenlaut. This letter also calls for “air filters for classrooms, specialist rooms and sanitary facilities in all schools”. TV satirist Jan Böhmermann, who is followed by almost two and a half million people on Twitter, wrote at the beginning of the month: “Wonder what the pandemic would look like if the air filter industry in Germany had such a powerful lobby as the car industry.”
A filter is not just a filter
There is no air filter. The political debate revolves mainly around mobile devices. There are also “air conditioning systems (HVAC)”, as it is called in technical jargon. These are permanently installed supply and exhaust air systems directly in the outer wall or ceiling or central ventilation systems that guide used air to the outside and fresh air to the inside via ventilation shafts throughout the building.
Billions for fixed assets, millions for mobile devices
According to the government, the federal government provided a good one billion euros in funding during the corona pandemic for the construction and conversion of such fixed systems in schools and daycare centers, which was also applied for or called up.
An additional 200 million euros were made available for the purchase of mobile devices in rooms that are difficult to ventilate, for example because windows can only be tilted open.
According to its own statements, Hamburg has purchased more than 21,000 mobile fans for 92 percent of the classrooms with a value of over 21 million euros. According to Education Minister Michael Piazolo (Freie Wahler), more than 70 percent of the classrooms in Bavaria are equipped with them. Compared to other federal states, the Free State currently has the most air purification devices.
No big difference?
Elsewhere, such as in Mecklenburg-Western Pomerania, large purchase programs have been dispensed with. The devices were too loud, not sustainable and would probably no longer be used after the pandemic, it was said in the north.
Representatives of the municipalities now see themselves confirmed. The use of the devices does not seem to make a very big difference, said Arp Fittschen from the Mecklenburg-Western Pomeranian City and Municipality Day of the German Press Agency, with a view to the lower corona numbers among children and young people in his state compared to Hamburg. And if you compare the incidences in children and adolescents in Bavaria, where many devices were purchased, with the nationwide figures, there are no major differences.
What the experts say
So mobile filters a bad investment? From the point of view of Hajo Zeeb from the Leibniz Institute for Prevention Research and Epidemiology in Bremen, that would be too short-sighted. “The effectiveness of mobile air filters cannot be deduced from a simple look at the incidences that are now prevailing across federal states, this requires targeted studies.” The devices are one of many measures in schools that could contribute to safety. “However, due to the high level of dynamics at Omikron, it is obviously no longer possible to keep the frequency of infections in children and young people at a low level.”
The aerosol researcher Birgit Wehner from the Leibniz Institute for Tropospheric Research says: “Basically, air filters always help to reduce the risk of infection. However, they are usually combined with other measures such as masks and ventilation, and this combination results in the individual risk. Therefore, the effects of individual factors are difficult to prove.”
Federal Environment Agency recommends fixed systems
Education politicians refer to the assessments of the Federal Environment Agency and the so-called S3 guideline for schools. In it, various scientific societies evaluate certain corona measures. When it comes to mobile air filters, the experts remain vague: “Overall (…) neither the positive nor the negative effects outweigh the negative effects, so that the measure can be considered”, but only as an “additional measure” to ventilation. A mobile air filter in the classroom would therefore not prevent children from having to sit in the classroom with down jackets.
The Federal Environment Agency considers mobile fans to be “useful” in places where windows can only be tilted to “minimize the likelihood of indirect infections” during the pandemic.
Gradually, however, the office recommends equipping the schools in the state with fixed HVAC systems. This is the “most sustainable measure to improve indoor air hygiene” even after the pandemic. The German Teachers’ Association demands that such solutions should be the future standard for school renovations and new school buildings.
Source: Stern
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