New Research Shows Masks and Ventilation Stop COVID Spread Better Than Social Distancing

For the study, the researchers created a computer model of a classroom with students and a teacher, then modeled airflow and disease transmission, and calculated air-powered transmission risk. Credit: Michael Kinzel, UCF

The results indicate that masks and good ventilation could be the key to allowing more capacity in schools, companies and other indoor spaces.

A new study from the University of Central Florida suggests that masks and a good ventilation system are more important than social distance in reducing the spread of COVID-19 in classrooms through the air.

The research, recently published in the journal Physics of Fluids, comes at a critical time when schools and universities are considering returning to more personalized classes in the fall.

“The research is important because it provides guidance on how we understand indoor safety,” said Michael Kinzel, an assistant professor in UCF’s Department of Mechanical and Aerospace Engineering and co-author of the study.

“The study finds that aerosol transmission routes do not require six feet of social distance when masks are mandatory,” he says. “These results show that with masks, the likelihood of transmission does not decrease with increasing physical distance, highlighting how mask mandates may be the key to increasing capacity in schools and other places.”

“The results suggest exactly what the CDC is doing, that ventilation systems and mask use are most important to prevent transmission and that social distance would be the first to relax.”

In the study, the researchers created a computer model of a classroom with students and a teacher, then modeled airflow and disease transmission, and calculated air-powered transmission risk.

The classroom was 709 square feet with 9-foot ceilings, comparable to a smaller university classroom, Kinzel says. The model had masked students – one of whom could be infected – and a masked teacher at the front of the classroom.

The researchers examined the classroom using two scenarios – a ventilated classroom and one non-ventilated – and using two models, Wells-Riley and Computational Fluid Dynamics. Wells-Riley is often used to assess the likelihood of indoor transmission, and Computational Fluid Dynamics is often used to understand the aerodynamics of cars, aircraft and the underwater movements of submarines.

Masks have been shown to be beneficial by preventing direct exposure to aerosols, as the masks release a faint cloud of warm air that causes aerosols to move vertically, preventing them from reaching neighboring students, Kinzel says.

In addition, a ventilation system in combination with a good air filter reduced the risk of infection by 40 to 50% compared to a classroom without ventilation. This is because the ventilation system creates a constant flow of air that circulates many of the aerosols in a filter that removes some of the aerosols compared to the no ventilation scenario where the aerosols congregate above the people in the room.

These results confirm recent guidelines from the U.S. Centers for Disease Control and Prevention that recommend reducing social distance in elementary schools from six to six feet when mask use is universal, Kinzel says.

“If we compare the chances of infection when wearing masks, one meter away from social distance does not indicate an increase in the chance of infection from 1.8 meters, which may prove that schools and other businesses can operate safely during the rest of the year. pandemic, ”said Kinzel says.

“The results suggest exactly what the CDC is doing, that ventilation systems and mask use are the most important to prevent transmission and that social distance would be the first thing to relax,” said the researcher.

When comparing the two models, the researchers found that Wells-Riley and Computational Fluid Dynamics generated similar results, especially in the non-vented scenario, but that Wells-Riley predicted the risk of infection by about 29 percent below in the vented scenario.

As a result, they recommend that some of the extra complex effects captured in Computational Fluid Dynamics be applied to Wells-Riley to gain a more complete understanding of the risk of infection in a space, says Aaron Foster, a doctoral student at UCF’s Department of Mechanical and Aerospace Engineering and the lead author of the study.

“While the detailed Computational Fluid Dynamics results provided new insights into the risk variation and distance relationships, they also validated the more commonly used Wells-Riley models because they captured most of the benefit of ventilation with reasonable accuracy,” said Foster. “This is important because these are publicly available tools that anyone can use to mitigate risk.”

Reference: “Estimating COVID-19 Exposure in a Classroom: A Comparison of Mathematical and Numerical Models” by Aaron Foster and Michael Kinzel, Feb. 24, 2021, Physics of Fluids.
DOI: 10.1063 / 5.0040755

The research is part of a larger overall effort to control airborne disease transmission and better understand factors associated with being a super-spreader. The researchers are also testing the effects of masks on the transmission distance of aerosol and droplets. The work is funded in part by the National Science Foundation.

Kinzel received his PhD in Aerospace Engineering from Pennsylvania State University and joined UCF in 2018. In addition to being a member of UCF’s Department of Mechanical and Aerospace Engineering, part of UCF’s College of Engineering and Computer Science, he also works with UCF’s Center for Advanced Turbomachinery and Energy Research.