Ventilation made easy

A simple ventilation system removes 90% of respiratory aerosols which potentially include coronavirus particles, from indoor air.

October 30, 2020

Joint press release issued by the MPI for Chemistry and the Integrated Comprehensive School Mainz-Bretzenheim

In future, it will be far easier to remove infectious aerosols from the air in classrooms and other spaces. Researchers at the Max Planck Institute for Chemistry have built a ventilation system that can be replicated using materials from a DIY store. A comprehensive school in Mainz has already tested the system. The Rhineland-Palatinate Ministry of Education is currently testing use of the system in other schools. The Mainz-based researchers will soon publish construction guidelines for replication online.

A simple exhaust air system for classrooms: Thomas Klimach assembles one of the hoods that will collect the warm air exhaled by students above a desk and direct it into the exhaust air duct. Also present: Roland Wollowski, Headmaster of IGS Mainz-Bretzenheim.

As the COVID-19 crisis continues, schools are faced with a problem: how to properly ventilate classrooms during lessons. Working together with the Integrated Comprehensive School Mainz-Bretzenheim, researchers at the Max Planck Institute for Chemistry have now successfully tested an exhaust air system that removes 90% of respiratory aerosol particles from classrooms. The principle behind this system is that every human being produces warm air that rises upwards. When this airflow is directed outside, it takes aerosol particles, and possible coronavirus particles, with it.

The design is incredibly simple and was implemented using DIY store materials worth about €200. A wide hood at 2m height, connected to a tube, hangs above each desk. All the tubes lead into a central duct, which in turn leads outside through a tilted window. A fan at the end of the duct ensures that the air is actively transported outside. Air inlet can be comprised of an open door or a second tilt-open window.

Aerosols are collected above each desk

The design is the brainchild of Frank Helleis, whose wife works as a teacher in Mainz. It was also through her that contact with the school was established. “It sounded so simple and convincing that we immediately decided to get involved,” says Roland Wollowski,

Headmaster at the Integrated Comprehensive School Mainz-Bretzenheim. This development quickly led to a prototype, which Frank Helleis and his colleagues assembled in a classroom over the summer and have been testing ever since.

“Our measurements have shown that the hood-based exhaust air system continuously removes over 90% of aerosols,” states Dr. Helleis. Although the simple system also works without the funnel-shaped hoods above the individual desks, they increase the efficiency significantly. The physicist proved this with aerosol spectrometers and artificially generated aerosols.

Dr. Helleis has deliberately designed the system for practical use. Due to its low material and operating costs, it could turn out to be a clever alternative to expensive filter systems and ventilation by shortly wide opening the windows. The modular system doesn’t take up much space (only requiring a power socket and a tilting window or skylight), so it’s also suitable for use in the likes of sports halls. Discussions as to whether the system can also be used at other schools in Rhineland-Palatinate are currently ongoing at the Rhineland-Palatinate Ministry of Education, which has already tested the functionality of the structure on site. “Our board of education, the City of Mainz, is also inspired by the project, and we are receiving constructive support in this respect,” reports Roland Wollowski. “We’re thrilled about the excellent cooperative relationship with the Max Planck Institute for Chemistry and have decided to kit out as many classrooms as possible over the coming weeks with the active assistance of the entire school community. Ventilation-related energy losses are also being reduced through this, which in turn benefits the climate.”

Instructions and contact form on the Institute’s website

Image 2: Schematic representation of the exhaust air system in a classroom.

At present, some manual skills are still needed to install the system, since the individual parts have to be assembled and mounted individually. To this end, Frank Helleis and his colleagues are preparing construction guidelines to keep the barrier for replication as low as possible. The Mainz researchers are also in contact with companies that could produce individual molded parts for the design, making it even easier to recreate.

Frank Helleis, who is known for being a creative inventor at the Max Planck Institute for Chemistry in Mainz, firmly believes that the system will remain in use after the pandemic.

“Our system also solves the long-standing problem of CO2 in classrooms, because it not only transports aerosols outside. It also cuts CO2 accumulation, helping students to concentrate better on their lessons.”

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