Making Higher Ed Safe: How Air Purifiers Can Reduce the Spread of Covid-19

Colleges and universities have been developing plans to reduce virus transmission in order to protect students and faculty’s health. 

Returning to face-to-face education means being exposed to the possibility of getting infected with SARS-CoV-2, the virus that causes Covid-19. Studies have shown that despite being vaccinated, infection and transmission of the virus is possible.

Some colleges and universities have imposed a mask mandate on their students and faculty when returning to campus. However, there is always a chance of accidentally breathing some potentially infected air. As we all know by now, the virus is airborne. Regular ventilation of classrooms and dorms is paramount. Yet, in crowded places such as educational institutions it is not enough.

Installing high-quality HEPA filter air purifiers in the classrooms, libraries, dorms, and offices across the institutions can protect students and academia against Covid-19 by keeping the air clean from viruses and bacteria. This is especially important while playing an instrument or singing in a confined room.

Assistant Professor Suo Yang, faculty member at the College of Science and Engineering, University of Minnesota, has found that the strategic placement of air purifiers can enhance good indoor air circulation, helping in mitigating the spread of infectious diseases such as Covid-19.

Simulation of virus aerosol in a music classroom

The video simulation below demonstrates the spread of virus aerosols throughout a music classroom with one student and one faculty member, both with and without portable air purifiers. The simulation was created by Assistant Professor Suo Yang who worked with the University of Minnesota College of Science and Engineering’s Music School to test the effectiveness of air purifiers in making in-person music instruction safer post-pandemic.

Yang is co-author of the research paper Risk Assessment of Airborne Transmission of Covid-19 by Asymptomatic Individuals under Different Practical Settings (PDF). This study is the first quantitative assessment of risks due to airborne transmission of viruses generated by asymptomatic individuals in a confined space under ventilation.   

According to the study, in indoor spaces, good ventilation will filter some of the virus out of the air, but may leave more viral particles on surfaces. In the classroom setting, after running a 50-minute simulation with an asymptomatic teacher consistently talking, the researchers found that only 10 percent of the aerosols were filtered out. The majority of the particles were, instead, deposited on the walls.

“Because this is very strong ventilation, we thought it would ventilate a lot of aerosols. But 10 percent is really a small number,” said Suo Yang. “The ventilation forms several circulation zones called vortexes, and the aerosols keep rotating in this vortex. When they collide with the wall, they attach to the wall. But, because they are basically trapped in this vortex, it’s very hard for them to reach the vent and actually go out.”

The study can lead to practical guidelines and science-driven policy for mitigating the risk of airborne infection of Covid-19 post-pandemic before fully re-opening universities and many businesses.

The results of the study suggest:

  • Optimizing ventilation setting can significantly improve the efficiency of particle removal
  • Adjusting the placement of occupants in the room to avoid hot spots and frequent cleaning of surfaces prone to contamination can reduce the risks
  • Wearing masks to cut down the source of particle generation can significantly lower the risk of airborne infection

Air purifiers improve overall air quality reducing virus spread

According to Yang, the strategic placement of air purifiers can help to mitigate the spread of the virus in indoor spaces. This is true not only for music classrooms but for any classroom and closed space. When evaluating approaches to mitigate the risk the best idea is ventilation, but if the ventilation is not enough, then adding air purifiers can enhance the ventilation.

According to the researchers, putting an air purifier in the direct flow path of the aerosol near where the air comes out of the instrument, one can reduce the number of potential virus aerosols being spread. As a result, the air purifiers in combination with the room’s original ventilation can remove more than 99 percent of the virus particles in the air of the room.

Yang advised the School of Music administrators to use portable air purifiers placed directly in front of the instruments or the student who is singing.

The School of Music has followed the advice and strategically placed air purifiers in every rehearsal space in order to deliver the safest possible educational experience.