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Study explores the spread of Covid-19 infected aerosols indoors

CAPE TOWN – A new study by the University of Minnesota College of Science and Engineering, has analysed the spread of Covid-19 indoors which may help schools and businesses take further precautions to reduce transmission.

Mechanical engineering associate professor Jiarong Hong and assistant professor Suo Yang based their experiment on the transmission via aerosols that are ejected from our mouths as we speak or exhale with the researchers finding that SARS CoV-2 virus attaches itself to these aerosols landing on nearby surfaces or directly inhaled by another person.

The experiment consisted of eight asymptomatic Covid-19 individuals with a precise measurement of aerosols released which were numerically captured allowing researchers to create a model on external flow in three different interior spaces such as an elevator, classroom, and a supermarket.

The researchers then went on to compare how ventilation on different levels within the environments affects the transmission of theses infected aerosols with simulations of ventilation systems inside an elevator or supermarket with inlets and outlets along with different faces of a ventilation box in classrooms.

The study found that good ventilation systems may filter some of the virus out the air but may still leave more viral particles on surfaces. With a 50-minute simulation on a classroom with an asymptomatic teacher consistently talking, they found that only 10 percent of aerosols were filtered out the air by a ventilation system but left the majority of particles deposited on walls.

“Because this is very strong ventilation, we thought it would ventilate out a lot of aerosols. But, 10 percent is really a small number,” said 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, and it’s very hard for them to reach the vent and actually go out.”

The simulation shows the transmission of infected aerosols with a ventilation system placed in two different areas with one directly above a teacher, which in most cases is doing the most talking, displays how significantly it reduces the spread of aerosols. This insight could inform how classrooms are arranged and help other businesses with their placing of ventilation systems too as lockdown restrictions begin to ease.

“After our work goes out, I think more people will ask for help because I think many businesses reopening will have this need—movie theatres, drama theatres, any place with large gatherings,” Yang said. “If you do a good job if you have good ventilation at the right location, and if you scatter the seating of the audience properly, it could be much safer.”

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