Max Planck researchers recommend window ventilation and fans for schools

Mainz - Window ventilation, supplemented by simple technical aids such as fans and extractor hoods, is very well suited to protecting against SARS-CoV-2 infections through aerosol transmission. This also applies in comparison to ventilation and air conditioning systems and to filter or UV radiation-based air purification devices. In addition, window ventilation also ensures good indoor air quality.

This is what scientists at the Max Planck Institute (MPI) for Chemistry in Mainz report. In a study, they examined the effectiveness of various approaches to infection protection ventilation and air purification. They previously published their results on the Open Science Repository Zenodo (DOI: 10.5281/zenodo.5070422). Publication in a scientific journal with a review process is still pending.

In their work, the researchers compare fan-assisted window ventilation systems and normal window ventilation (intermittent and continuous ventilation) with ventilation and air purification devices based on carbon dioxide and aerosol measurements and model calculations based on them for a teaching day in a typical classroom.

A combination of displacement ventilation, in which fresh air flows into the room through a window at ground level, and distributed exhaust air extraction over potentially infectious people is particularly effective. This can be achieved, for example, by a tilted window behind a curtain or porch. The students' warm breathing air rises, and a fan in or in front of the window blows the air outside, according to the approach.

"Overall, the comparison shows that window ventilation systems with exhaust air fans are not only inexpensive and easy to implement. They are also very effective in keeping the air clean and counteract the aerosol transmission of infectious diseases such as COVID-19 or influenza," said Frank Helleis, head of instrument development at the MPI for Chemistry.

In his opinion, the recovery of heat or moisture does not bring any significant advantages either in terms of energy or the indoor climate. “It makes much more sense to supply outside air through the windows according to the displacement air principle. Treating fresh air with technical components increases the maintenance effort and can cause hygiene problems,” says the scientist.

The Mainz researchers therefore recommend exhaust air fans in all classrooms that are not yet equipped with similarly effective aids - not only to contain the pandemic, but also to improve the air quality in school classes in general.

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According to a study by the University of Stuttgart, the effectiveness of mobile air filters in classrooms to protect against the corona virus is limited. In their analysis commissioned by the city of Stuttgart, the experts are against purchasing such devices for all schools.

The study, which is available to the German Press Agency, states: "Based on the findings from the pilot project, the widespread use of air purification devices is not indicated (indicated)." In individual classrooms that have too small or too few windows However, the use of mobile devices or the installation of stationary filters should be planned.

For the study, the experts from the Institute for Building Energetics, Thermotechnology and Energy Storage measured the effect of the filters at ten schools in Stuttgart for six months. They now warn that the devices are not a substitute for airing during breaks.

"When using air purification devices, it should generally be noted that these are not an alternative to changing the outside air, but should only be used to help reduce particles and potential viruses in the room."

In summary, the experts state that the use of air purification devices cannot replace other protective measures such as wearing a mask or testing to contain the spread of infection. © hil/dpa/aerzteblatt.de