Plexiglas shields have become ubiquitous at offices, grocery stores and restaurants across the country in the coronavirus age. They were even installed on the U.S vice presidential debate. Given that they are just about everywhere, you may wonder how effective they actually are.

Businesses and workplaces have pointed to Plexiglas dividers as one tool they are using to keep people safe against the spread of the virus. But it’s important to know there’s little data to support their effectiveness, and even if there were, the barriers have their limits, according to epidemiologists and aerosol scientists, who study airborne transmission of the virus. 

The U.S Centers for Disease Control and Prevention (CDC) has offered guidance to workplaces to “install physical barrier, such as clear plastic sneeze guards, where feasible” as a way to “reduce exposure to hazards”, and the U.S Labour Department’s Occupational Safety and Health Administration (OSHA) has issued similar guidance. 

That’s because the Plexiglas shields can in theory protect workers against large respiratory droplets that spread if someone sneezes or coughs next to them, say epidemiologists, environmental engineers, and aerosol scientists. Coronavirus is thought to spread from person to person “mainly through respiratory droplets produced when an infected person coughs, sneezes or talks”, according to the CDC. 

Most droplets people release when they talk or breathe are in a “size range that will flow past the barrier” said Pratim Biswas, an aerosol scientist at Washington University in St. Louis. The dividers do not address all possible modes of transmission, such as aerosol transmission, or fully protect anyone from COVID-19. 

The National Restaurant Association said in a statement that Plexiglas shields and barriers are a tool that when combined with other practices – like face coverings, appropriate social distancing and handwashing – provide an additional level of safety.

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