Scientists who didn't do well in school

"I do not share the opinion given in the press release": How the KMK misrepresents a hearing on air filters in classrooms

BERLIN. In the week before last, the Conference of Ministers of Education reacted to demands that classrooms be equipped with mobile air filter systems against aerosols possibly contaminated with corona. The - alleged - result, announced in a subsequent press release: "The scientists agreed that the use of such devices was basically not necessary." According to research by News4teachers, however, this representation is incorrect. The only scientist present who has done research on the subject considers the use of air filters in schools to be very necessary - and explained this to the ministers of education in the group.

"If we want to prevent schoolchildren from getting infected with the corona virus in winter, we need a mobile air filter in every classroom," said SPD health expert Prof. Karl Lauterbach, an epidemiologist himself, a good month ago. Sufficient and regular ventilation of the classrooms is not possible in the winter months. In addition, wearing a mask for a long time would not effectively protect the students from infections in the drier winter air. "That is why I appeal to the Prime Ministers of the federal states to quickly decide on the purchase of the air filter systems in September," said Lauterbach. The production could take place in Germany. However, it takes several months, which is why the decision must be made now so that they are available in winter.

The KMK apparently wanted to put an end to the debate about air filters in schools

Lauterbach referred to a study by the Institute for Fluid Mechanics and Aerodynamics at the University of the Federal Armed Forces in Munich, in which the effect of room air purifiers had been examined. Result: Commercially available mobile devices can also effectively reduce the concentration of infectious aerosol concentrations in larger rooms. Since then, the discussion about whether the state governments should invest in air filters for schools has been hot.

The Conference of Ministers of Education and Cultural Affairs (KMK) apparently wanted to put an end to this debate - with an expert hearing on the subject on September 23. In addition to the doctor Prof. Dr. med. Martin Exner, Director of the Institute for Hygiene and Public Health, the virologist Prof. Dr. Bodo Plachter, the hospital hygienist Dr. Wolfgang Kohnen, also Dr. Heinz-Jörn Moriske from the Federal Environment Agency and Prof. Dr. Christian J. Kähler - head of the air purifier study - has been invited.

According to the KMK, the result of the round was clear: “The experts agreed that ventilation in classrooms was an essential part of the hygiene and infection protection measures already in place in schools. They advised intermittent ventilation (opening the window wide) at intervals of 20 minutes and for around 3 to 5 minutes, as well as cross-ventilation (draft) of the rooms during the breaks ”, according to a press release that the KMK subsequently issued. It also says: “The use of mobile air purification devices in classrooms, which is currently being discussed intensively in public, was also discussed. As a result, the scientists agreed that the use of such devices is generally not necessary where rooms can be ventilated through windows. "

"The method of free ventilation in schools has its limits"

The representation is wrong, however. "I do not share the opinion stated in the press release because my experimental analyzes do not support this opinion," said Kähler when asked by News4teachers. "According to our scientific analyzes, room air purifiers that manage an air exchange rate of at least 6 per hour, use a class H14 filter and are sufficiently quiet that they are not switched off, offer a much higher level of security against indirect infection than free ones Ventilation. ”And this is what he said in the panel of experts with the ministers of education; the KMK press release had not been coordinated with him.

In fact, it says in a paper in which Kähler - incidentally the only one in the group who has researched the effect of air filters - describes the results of his work: “The quantitative measurement results show beyond any doubt that the method of free ventilation, as used by many Schools has its limits. In order to achieve an air exchange rate of 6 per hour with the method of free ventilation, at least 3.5 or 2.5 doors of the specified size in the room would have to be permanently open with these temperature differences and wind conditions. It is questionable whether classrooms have such large window openings. It must also be taken into account that the outside and room temperatures are becoming more and more similar and therefore a large number of air changes cannot be maintained in practice over the long term. Due to the inadequate effectiveness of free ventilation, we consider safety concepts that are based solely on free ventilation to be unsafe. "

According to Kähler, a mobile air filter system that has the necessary properties costs around 3,000 euros. According to him, another 500 euros per classroom should be invested in Plexiglas protective walls between the students in order to avoid direct infections. According to Kählert, he spoke to manufacturers. They had the capacity to equip schools in Germany with a large number of devices at short notice.

NRW School Minister Gebauer has given the direction: too expensive

But politics must also want that. NRW School Minister Yvonne Gebauer (FDP) had already given the direction at the end of August. She thinks air filters in classrooms against the corona virus are too expensive, she said at the time. At around 3,000 euros per class, the devices would “devour huge sums”. Lauterbach sees it differently, however. The SPD politician decided that the air filters could certainly be financed. “An air filter system costs a maximum of 100 euros per student. The children should be worth it to us. The state even supported companies in the Corona crisis with a multiple of this amount on a weekly basis. " News4teachers

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Students and teachers must dress warmly! KMK considers ventilation against corona-contaminated aerosols to be sufficient - even in winter