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Plexiglass dividers at the VP debate won't do much, experts say

Kamala Harris requested the plexiglass barriers in response to Mike Pence’s potential exposure to President Donald Trump.
Image: Plexiglass installed onstage for the vice presidential debate in Salt Lake City
Commission on Presidential Debates staff clean the freshly installed protective plexiglass panels put in place as a coronavirus disease precaution between the candidates' seats for the 2020 vice presidential debate.BRIAN SNYDER / Reuters
/ Source: NBC News

When Vice President Mike Pence and Sen. Kamala Harris square off on the debate stage Wednesday night, a pair of plexiglass barriers will separate them.

The barriers are just one of the coronavirus precautions being added for the debate. Pence and Harris will also be positioned 12 feet from each other, instead of 7 feet. And they have each been tested for the coronavirus, as have people attending the event, who will be required to wear masks.

But despite being treated as a safety measure, the plexiglass barriers will be almost entirely for show, said Jose-Luis Jimenez, a chemistry professor at the University of Colorado who studies how the coronavirus can spread through the air.

"Aerosol transmission is basically like smoke," Jimenez said. "If one of the candidates is smoking and you put up plexiglass barriers, it won't matter. The smoke will just go around those barriers."

The extra precautions were put in place after the White House emerged as a coronavirus hot spot and with mounting evidence of the risks of airborne transmission of Covid-19. Experts say the partitions do not provide adequate protection for the candidates or the attendees.

Harris, the Democratic vice presidential nominee, requested the plexiglass barriers in response to Pence's potential exposure to President Donald Trump, who tested positive for Covid-19 last week and was hospitalized for several days. Pence initially rejected the need for the dividers, but his team has since backed down.

Airborne transmission is a known risk. Both the World Health Organization and the Centers for Disease Control and Prevention have expanded their guidance on the coronavirus to include the possibility of airborne transmission, which means the virus could be spread through tiny droplets, or aerosols, that linger in the air.

But plexiglass barriers primarily shield against droplets that get expelled when people cough, sneeze, speak or sing. Droplets can carry the coronavirus, but this type of transmission is unlikely to be as much of an issue if the debaters are 12 feet apart.

"Plexiglass barriers are designed to keep somebody's spit from hitting you in the face, but when you're distanced, any spit that flies out of your mouth will drop to the ground, but aerosol particles will remain aloft and mix into the space," said Shelly Miller, a professor of environmental engineer at the University of Colorado Boulder.

Ensuring that a space is properly ventilated is the most effective way to protect against aerosol transmission indoors, Miller said.

Guidelines from the American Society of Heating, Refrigerating and Air-Conditioning Engineers suggest that HVAC systems outfitted with the highest-grade filters that do not affect airflow could keep virus-laden aerosols from circulating indoors. Portable air cleaners with HEPA (high-efficiency particulate air) filters could also be used to disinfect indoor air, according to the professional organization, which has more than 57,000 members worldwide.

"You want to make sure you're inhaling as little as possible of the air exhaled by other people," Jimenez said.

The Commission on Presidential Debates has not made public any information about ventilation systems inside the debate hall.

Though there are only hours remaining until the candidates take the stage, there are ways to make last-minute safety adjustments using off-the-shelf products, according to Dr. Donald Milton, a professor of environmental health at the University of Maryland.

Milton and his colleague Jelena Srebric, a professor of mechanical engineering at the University of Maryland, simulated conditions with a person singing while flanked by two box fans equipped with HEPA filters, each spaced roughly 3 feet apart. The researchers found that they could reduce the particle concentration in the air by 50 percent by using the fans to suck in the singer's exhaled air and scrubbing it with the filters.

The experiments were initially designed to test how music teachers could safely resume classes, but Milton and Srebric said the same principles could be applied to the vice presidential debate. The scientists submitted a letter Tuesday to the Commission on Presidential Debates outlining the results of their simulation and offering to help implement similar systems in the debate hall in Salt Lake City.

So far, they haven't heard anything in response, but they remain hopeful.

"We've made a lot of efforts to reach out to people, both on the Republican and Democratic side," Milton said.

Yet even if precautions are taken for Wednesday's debate, some experts were concerned about the message that it could send to Americans watching from home.

"It's not just whether this is risky for the two candidates, it's also about the kind of example we set," Jiminez said. "If we show that it's OK to be indoors without masks at some distance, then we're communicating to people that it's safe — but in general, that is not safe."

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