We know that plastic face shields are ineffective at preventing the transmission of the airborne coronavirus. Shields should only be used in conjunction with masks that go over the nose and mouth. What about the plastic barriers that went up last year in grocery stores, gas stations and offices? We’ve been under the impression that those must work somewhat to help keep people safe. The New York Times has a new article about barriers, citing multiple studies and quoting engineers and scientists. Studies show that plastic barriers are only good at blocking large droplets. Unless a room is designed by an airflow specialist, the barriers can work to concentrate aerosols in a smaller area. The Times tells readers to imagine aerosols like cigarette smoke. If you had people smoking (talking) in a room all day, of course giant shields would trap that air somewhat. Here’s some of that article, with more at the source:
Intuition tells us a plastic shield would be protective against germs. But scientists who study aerosols, air flow and ventilation say that much of the time, the barriers don’t help and probably give people a false sense of security. And sometimes the barriers can make things worse.
Research suggests that in some instances, a barrier protecting a clerk behind a checkout counter may redirect the germs to another worker or customer. Rows of clear plastic shields, like those you might find in a nail salon or classroom, can also impede normal air flow and ventilation.
Under normal conditions in stores, classrooms and offices, exhaled breath particles disperse, carried by air currents and, depending on the ventilation system, are replaced by fresh air roughly every 15 to 30 minutes. But erecting plastic barriers can change air flow in a room, disrupt normal ventilation and create “dead zones,” where viral aerosol particles can build up and become highly concentrated…
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.
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.
Early this year, well before vaccines were available, I went to pay taxes at my local county office. None of the staff inside had masks on and instead used plastic barriers with giant openings at the bottom separating them from the public. The county office one town over had an outbreak two weeks prior to that. I was mortified to see that but I felt somewhat safe because I was double masked. I kept my mouth shut because those people can make my life miserable. Plus I figured that they would learn the hard way soon enough.
The only thing surprising about these findings is that fact that it took so long for this to become public. Engineers have known this and some of these studies were conducted years ago using other airborne diseases. I guess we’ve been so busy fighting multiple battles that the plastic shield issue seemed like a minor one. I’m tired but the only thing I can do is continue to wear a mask, socially distance and get the booster shot when it’s available.
Maybe shields that allow for air flow are OK though, like this one which just separates staff and customers:
photos credit: Avalon.red and via Instagram