This Kind of Face Covering Won't Protect You From COVID, Study Warns
They may be more comfortable, but data shows they're just not as safe.
By now, medical experts agree that wearing a face covering is one of the best ways to slow the spread of coronavirus, especially if it's done in combination with social distancing and regular hand washing. And while some may disagree on exactly which type is the best overall, it's also becoming clear that certain kinds of face coverings can be less effective. According to one recent study, face shields won't protect you from COVID as well as traditional masks do.
The new research, which was just published in the journal Physics of Fluids, finds that while face shields are capable of stopping large droplets expelled with coughing, sneezing, or loud talking, they don't fully keep potentially contaminated aerosols from traveling around the plastic visor and moving around the room. "Over time, these droplets can disperse over a wide area in both the lateral and longitudinal directions, albeit with decreasing droplet concentration," the study authors wrote.
The study also found that masks with ventilation holes were similarly inadequate for protecting against the spread of COVID, saying that droplets were able to pass freely through the valve and out into the general space. In contrast, some non-surgical grade face masks were able to contain aerosol droplets from traveling forward, even when violently expelled during coughing or sneezing.
Data was collected through a visualization that used a mannequin's head connected to a fog machine and pump. A "laser sheet" was then used to illuminate the vapor being passed through the mannequin's head, which was outfitted with a face covering and simulated different behaviors such as breathing, talking, coughing, or sneezing, Live Science reported. During the face shield simulation, it was found that while many particles were directed towards the ground, some were able to float near the bottom of the visor before floating in the air up to three feet away from the mannequin.
Other studies have upheld the findings that one type of face covering can do more than others to stop the spread of COVID. An August article in Nikkei Asian Review showed that a Japanese supercomputer known as "Fugaku" ran droplet spreading simulations involving different types of masks. The results showed that standard light-blue disposable medical masks were the most effective at containing potentially contaminated aerosols, stopping nearly all particles versus the 80 percent stopped by masks made of woven material or polyester.
This data is also in line with the current Centers for Disease Control and Prevention (CDC) guidelines, which state, "At this time, it is not known what level of protection a face shield provides to people nearby from the spray of respiratory droplets from the wearer … Therefore, CDC does not currently recommend the use of face shields as a substitute for masks." And for more on how you can make your PPE even more effective, If We All Do This "The Pandemic Would Probably Die Off," Scientist Says.