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Most researchers say the screens most likely help in very specific situations. A bus driver, for instance, shielded from the public by a floor-to-ceiling barrier is probably protected from inhaling much of what passengers are exhaling. A bank cashier behind a wall of glass or a clerk checking in patients in a doctor’s office may be at least partly protected by a barrier.
A study by researchers with the National Institute for Occupational Safety and Health in Cincinnati tested different sized transparent barriers in an isolation room using a cough simulator. The study, which hasn’t yet been peer-reviewed, found that under the right conditions, taller shields, above “cough height,” stopped about 70 percent of the particles from reaching the particle counter on the other side, which is where the store or salon worker would be sitting or standing.
But the study’s authors noted the limitations of the research, particularly that the experiment was conducted under highly controlled conditions. The experiment took place in an isolation room with consistent ventilation rates that didn’t “accurately reflect all real-world situations,” the report said.
The study didn’t consider that workers and customers move around, that other people could be in the room breathing the redirected particles and that many stores and classrooms have several stations with acrylic barriers, not just one, that impede normal air flow.
While further research is needed to determine the effect of adding transparent shields around school or office desks, all the aerosol experts interviewed agreed that desk shields were unlikely to help and were likely to interfere with the normal ventilation of the room. Depending on the conditions, the plastic shields could cause viral particles to accumulate in the room.
“If there are aerosol particles in the classroom air, those shields around students won’t protect them,” said Richard Corsi, the incoming dean of engineering at the University of California, Davis. “Depending on the air flow conditions in the room, you can get a downdraft into those little spaces that you’re now confined in and cause particles to concentrate in your space.”
Aerosol scientists say schools and workplaces should focus on encouraging workers and eligible students to be vaccinated, improving ventilation, adding HEPA air filtering machines when needed and imposing mask requirements — all of which are proven ways to reduce virus transmission.
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