New Delhi (NVI): Masks and a good ventilation system are more important than social distancing for reducing the airborne spread of COVID-19 in classrooms, a study from the University of Central Florida suggested.
The research, published recently in the journal Physics of Fluids, the researchers created a computer model of a classroom with students and a teacher then modeled airflow and disease transmission, and calculated airborne-driven transmission risk.
The classroom model was 709 square feet with 9-foot-tall ceilings, similar to a smaller-size, university classroom.
The model had masked students — any one of whom could be infected — and a masked teacher at the front of the classroom.
Michael Kinzel, an assistant professor in UCF’s Department of Mechanical and Aerospace Engineering and study co-author said, “The research is important as it provides guidance on how we are understanding safety in indoor environments.”
“The study finds that aerosol transmission routes do not display a need for six feet social distancing when masks are mandated,” he added.
He said these results highlighted that with masks, transmission probability does not decrease with increased physical distancing, which emphasizes how mask mandates may be key to increasing capacity in schools and other places.
The team of researchers examined the classroom using two scenarios — a ventilated classroom and an unventilated one — and using two models, Wells-Riley and Computational Fluid Dynamics. Wells-Riley is commonly used to assess indoor transmission probability and Computational Fluid Dynamics is often used to understand the aerodynamics of cars, aircraft and the underwater movement of submarines.
Masks were shown to be beneficial by preventing direct exposure of aerosols, as the masks provide a weak puff of warm air that causes aerosols to move vertically, thus preventing them from reaching adjacent students, Kinzel said.
According to the researchers, a ventilation system in combination with a good air filter reduced the infection risk by 40 to 50% compared to a classroom with no ventilation.
Kinzel said that these results corroborate recent guidelines from the US Centers for Disease Control and Prevention that recommend reducing social distancing in elementary schools from six to three feet when mask use is universal.
“If we compare infection probabilities when wearing masks, three feet of social distancing did not indicate an increase in infection probability with respect to six feet, which may provide evidence for schools and other businesses to safely operate through the rest of the pandemic,” said Kinzel.
When comparing the two models, the researchers found that Wells-Riley and Computational Fluid Dynamics generated similar results, especially in the non-ventilated scenario, but that Wells-Riley underpredicted infection probability by about 29 per cent in the ventilated scenario.
As a result, they recommend some of the additional complex effects captured in Computational Fluid Dynamics be applied to Wells-Riley to develop a more complete understanding of risk of infection in a space, says Aaron Foster, a doctoral student in UCF’s Department of Mechanical and Aerospace Engineering and the study’s lead author.
The research is part of a larger overall effort to control airborne disease transmission and better understand factors related to being a super-spreader. The researchers are also testing the effects of masks on aerosol and droplet transmission distance. The work is funded in part by the National Science Foundation.
–PRT
