Research finds that wearing masks and maintaining ventilation are better than maintaining social distancing to stop the spread of the new coronavirus
Recently published on “Physics of Fluids” The research paper comes at a critical moment when American schools and universities are considering the start of the fall.
“This research is very important because it provides guidance on how to understand safety in indoor environments,” said Michael Kinzel. Kinzel is an assistant professor in the Department of Mechanical and Aerospace Engineering at UCF and a co-author of this research paper.
He pointed out: “Studies have found that when a mask must be worn, aerosol transmission does not require a 6-foot social distance. These results emphasize that with a mask, the possibility of transmission is not It will decrease with the increase of physical distance, which emphasizes that the requirement to wear masks may be the key to improving the ability of schools and other places (epidemic prevention).”
In this study, the researchers created a A computer model of a classroom with students and teachers, then modeled airflow and disease transmission and calculated the risk of air-driven transmission.
The classroom model is 709 square feet with 9-foot ceilings. In the model, there are a student wearing a mask and a teacher who also wears a mask, the latter standing in front of the classroom.
The researchers used two scenarios-a ventilated classroom and an unventilated classroom-and used two models, Wells-Riley and computational fluid dynamics. Wells-Riley is commonly used to evaluate the probability of indoor propagation, and computational fluid dynamics is commonly used to understand the aerodynamics of cars, airplanes and submarines.
Kinzel said that wearing a mask has proven to be beneficial by preventing direct exposure to aerosols because the mask provides a weak warm air that causes the aerosols to move vertically and prevents them from contacting nearby students. .
In addition, compared with a classroom without ventilation, a ventilated classroom combined with a good air filter can reduce the risk of infection by 40% to 50%. This is because the ventilation system creates a stable air flow, which allows a lot of aerosols to enter the filter. Compared with the unventilated situation, the aerosols gather above the people in the room and filter out a part of the aerosols.
Kinzel said that these results confirm the recent guidelines of the US CDC, which recommends reducing social distance in elementary schools from 6 feet to 3 feet when masks are widely used.
“If we compare the chance of infection while wearing a mask, a social distance of three feet does not mean that the chance of infection is higher than six feet. This may be safe for schools and other businesses during the remaining time of the pandemic. Operations provided evidence,” Kinzel said.
When comparing the two models, the researchers found that Wells-Riley and computational fluid dynamics produced similar results, especially in the case of no ventilation, but Wells-Riley would The probability of infection is underestimated by about 29%.
The lead author of this study, Aaron Foster, said that in this regard, they recommend that some additional complex effects captured in computational fluid dynamics be applied to Wells-Riley to develop a A more complete understanding of the risk of infection in a space.
“Although the detailed computational fluid dynamics results provide a new perspective on risk changes and distance relationships, they also verify that the more commonly used Wells-Riley model captures most of the ventilation with reasonable accuracy Benefits. This is important because these are public tools that anyone can use to reduce risk.”