August 23, 2021 -- Plastic barriers that separate people in stores, restaurants, and classrooms may not be as effective at stopping the spread of COVID-19 as originally thought, according to The New York Times.
Scientists who study air flow, ventilation and aerosol droplets say the barriers may not help, and in fact, could make the situation worse by blocking normal air flow, the newspaper reported.
Typically, as people interact and breathe in a room, currents and ventilation systems recirculate the air and disperse the exhaled particles. With plastic barriers, however, particles could get trapped in “dead zones” and build up.
“If you have a forest of barriers in a classroom, it’s going to interfere with proper ventilation of that room,” Linsey Marr, professor of civil and environmental engineering at Virginia Tech, told the newspaper.
“Everybody’s aerosols are going to be trapped and stuck there and building up, and they will end up spreading beyond your own desk,” she said.
Several variables factor into the efficacy of plastic barriers, The New York Times reported. Shields may stop big respiratory droplets from coughs and sneezes, for instance, but they may not do much to prevent small aerosol particles from viruses such as COVID-19 from spreading.
“We have shown this effect of blocking larger particles, but also that the smaller aerosols travel over the screen and become mixed in the room air within about five minutes,” Catherine Noakes, a professor of environment engineering at the University of Leeds, told the newspaper.
“This means if people are interacting for more than a few minutes, they would likely be exposed to the virus regardless of the screen,” she said.
The effectiveness of plastic barriers likely also depends on the location and setup, the newspaper reported. A bus driver with a large barrier, for instance, may be able to avoid inhaling the particles that passengers are exhaling. A bank cashier or store clerk behind a large barrier may also be partly protected.
Even still, scientists say more research is needed. For instance, taller barriers are more likely to be effective. However, a large number of barriers in one room could likely block air flow.
Researchers have recommended that schools and offices focus on ventilation, masks, and vaccines to slow the spread of the coronavirus.
“Air flow in rooms is pretty complicated,” Richard Corsi, dean of engineering at the University of California at Davis, told the newspaper.
“Every room is different in terms of the arrangement of furniture, the height of the walls and ceilings, the vents, where the bookshelves are,” he said. “All of these things have a huge impact on the actual flow and air distribution in a room.”