Most of the children in Germany are back in school. But even for the second Corona school year, by far not all schools are equipped with filter systems. Many are looking for alternative solutions. The Max Planck Institute for Chemistry has developed one. It costs little and can be installed by the schools themselves with little effort.
It may look a bit strange, but it is inexpensive and only requires a little handicraft skill: Large umbrellas on the ceiling above the students, connected with plastic pipes and fans.
Thought up by scientists
This do-it-yourself exhaust air system was devised last year by scientists from the Max Planck Institute for Chemistry (MPI) and has even been implemented on a large scale. The city of Mainz has now equipped around 75 percent of all classrooms with ventilation devices, most of them with the MPI systems, as Eckart Lensch (SPD) says.
The construction is very light and poses no danger to the children if something should come loose
In addition, there are around 500 systems in Landau, as well as several hundred in various other cities, reports Frank Helleis, one of the fathers of the system and physicist at the MPI. There are currently also inquiries from Bavaria.
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The cooker hood principle
How do the systems work? The system collects stale air in the umbrellas directly above the students, before the air is distributed in the room, explains Helleis. In the system, this air is then transported outside through the pipes through a window and replaced by fresh air that flows in through another window.
For this purpose, the warm air flowing upwards is used, which is created by the body temperature of the students themselves, explains the physicist. Together with the exhaled air, CO2 and the aerosols would also be carried upwards. “When it arrives at the ventilation system, the stale air is extracted in a targeted manner, like with an extractor hood, and directed outside via a pipe system,” says the description.
The normal air currents of a classroom …
… are actively used and reinforced by the MPIC filter system
More efficient than air purifiers
The scientists can now also refer to their study results. “We took measurements all winter,” says Helleis. The conclusion: “The scientific comparison shows that fan-assisted window ventilation can be used more effectively against the aerosol transmission of Covid-19 and to improve the air quality in school classes than more complex ventilation and air purification devices.”
From the point of view of the Federal Environment Agency (UBA), this test report confirms “that the systems are suitable for removing used – and possibly virus-contaminated – air from school rooms and for supplying fresh outside air”, as a spokeswoman in Berlin announced on request. “We do not expressly recommend this type of system because the necessary prerequisites for their installation and operation may not be met in all schools.” However, this does not mean “that the systems are not effective and we do not consider them useful”.
Costs between 300 and 100 euros
The first systems were installed in Mainz around a year ago, so the head of the pioneering school was even invited to the Federal President’s festival for people who stood out with special ideas during the pandemic, as Head of Department Lensch reports. “What speaks in favor of the systems is that they can be installed quickly and by laypeople.” At the building management company Mainz (GWM) there is an employee who is responsible for the installation. “The materials come more or less from the hardware store.” The in-house company GWM is basically also responsible for maintenance. “And even if part of the system falls down, it sails quietly to the ground. That is very easy.”
Helleis puts the material costs per classroom at around 300 to 1000 euros. “That depends on the fans.” But that is still significantly cheaper than standard devices, which cost around 4,000 euros.
The Max Planck Institute for Chemistry has one Step-by-step instructions put on the Internet. Time expenditure and material lists are given and some steps are shown in the video.
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