Can ventilation and air purification systems protect against Covid-19? How do they need to be designed? And how must hygiene and ventilation concepts be designed to reduce virus transmission through aerosols? Answers to these questions are being provided by a research team from the Fraunhofer Institutes IBP, IGB and IPA in a new consulting center for healthy indoor air. At the same time, IBP and IPA are conducting a study to investigate how ventilation systems affect the spread of aerosols. The consulting center and study are part of the "Healthy Air Initiative" of the Baden-Württemberg Ministry of Economic Affairs, Labor and Housing.
In December 2020, the Ministry of Economic Affairs, Labor and Housing adopted the Healthy Air Initiative, an integrated consulting and research program. "In the current pandemic situation, small and medium-sized companies in particular have a great need for advice on aerosol avoidance. With the Healthy Air Initiative, we want to show our companies quick and practical, scientifically sound solutions for room ventilation to prevent aerosols," said Minister Dr. Nicole Hoffmeister-Kraut.
The three Stuttgart-based Fraunhofer Institutes IBP, IGB and IPA are therefore setting up the joint consulting center for healthy room ventilation. Here they help small and medium-sized companies from Baden-Württemberg to implement ventilation concepts. Together with manufacturers, they operate test environments and carry out effectiveness tests on air purification technologies. A study is also being carried out to examine how mobile and permanently installed ventilation systems affect the spread of infectious SARS-CoV-2 aerosols.
Investigations into the conversion and redesign of ventilation systems
Ventilation and air purification systems were originally developed to filter out dust and stuffy air from indoor spaces and draw in fresh air from outside. For a long time, hardly anyone was interested in how they affected the spread of viruses. Then came corona and it has been clear ever since: ventilation systems in combination with air conditioning technology can promote the spread of SARS-CoV-2 in closed rooms. "The colder and drier the air, the easier it is for the virus to spread," says Dr. Udo Gommel, Head of Automation and Cleanliness Technology at the Fraunhofer Institute for Manufacturing Engineering and Automation IPA. "This is because the tiny water droplets that may contain the virus evaporate more quickly and it floats around the room for longer," adds Professor Dr. Gunnar Grün, Deputy Director of the Fraunhofer Institute for Building Physics IBP.
As constant or frequent ventilation is hardly an alternative, and not just in the cold season, existing ventilation and air purification systems need to be converted and new ones need to be designed differently. But how differently? And how exactly do existing ventilation systems without air conditioning technology affect the spread of SARS-CoV-2? This is exactly what a research team now wants to find out in a joint study.
Decontamination of filters
To do this, the scientists want to gain an overview: Which fixed or mobile ventilation devices are available on the market? What effect do they have on viral load, particles, noise and comfort in closed rooms? "Of course, we also focus on sustainable aspects, such as the practical use, maintenance and energy consumption of the devices," says Professor Grün. The theoretical considerations first lead to simulations and then to practical tests. The research team would like to carry out tests with the systems in the Fraunhofer IPA clean room, in the laboratories of Fraunhofer IBP and IGB or simply where they are already installed, for example in meeting and conference rooms or workplaces. There, together with manufacturers of ventilation and air purification systems, they will simulate various scenarios and evaluate how they affect aerosol distribution in the room. In this way, reliable findings can be obtained quickly.
The end result will be concrete proposals on how ventilation systems need to be improved or retrofitted to prevent the spread of SARS-CoV-2 as far as possible. However, one thing is already foreseeable: "If ventilation systems filter pathogens out of indoor spaces, their filters are contaminated with viruses," says study leader Gommel. "So the filters can be irradiated with ultraviolet light, for example, which inactivates the viruses. As this UV radiation is harmful to the human eye and skin, the irradiation must be shielded in a specially designed housing or area."
Tests with model viruses show effectiveness of air purification technologies
Parallel to the study, Gommel, Grün and their colleague Professor Dr. Susanne Bailer from the Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB are setting up the Consulting Center for Healthy Indoor Air. It serves small and medium-sized companies from
Baden-Württemberg as a point of contact for all questions regarding the design of room ventilation in times of the pandemic. Suitable test stands are to be set up especially for manufacturers in order to investigate the effectiveness of air purification technologies. "In order to be able to make the most reliable statements possible, we are working with so-called surrogate viruses. These model viruses used for the practical test are very similar to the novel coronaviruses, but are harmless to humans and the environment," explains virus expert Bailer. "By analyzing the viruses before and after air pollution control measures in terms of their activity and quantity, we can draw conclusions about necessary adjustments to ventilation systems or inactivation steps." In order to also meet the information needs of suppliers and manufacturers of ventilation and air purification systems, the researchers share their experience from consulting practice with these companies.
Aerosols also dangerous in other areas of life
The Healthy Air Initiative will run for one year and is being funded with 2.7 million euros. The free online event "Meet (y)our experts" on the topic of air purification will take place at the start on March 3, 2021 (see info box). The scientists involved will provide information about their advisory center and explain how companies can get involved. The research team will report on new findings in subsequent, similar webinars.
The study results, which should be available at the beginning of 2022, could serve as the foundation for further investigations. Aerosols are also a serious problem as carriers of other infectious viruses and in other areas of life: from air pollution caused by particulate matter and nitrogen oxides in numerous major German cities, to toxic fumes in aircraft cabins and material vapors in buildings, to toxic or conductive particles that disrupt battery cell production. On the basis of further studies, the industry would be able to develop effective and cost-effective ventilation and air purification systems for a wide range of applications in the future.
