FAU Study Finds Certain Face Coverings Ineffective for Protecting Against COVID-19
A new study conducted by Florida Atlantic University’s College of Engineering and Computer Science finds that face shields and masks with valves do not aid in preventing the spread of COVID-19. In fact, they may have adverse effects.
The study done by researchers at FAU’s College of Engineering and computer science was conducted in order to increase public awareness about the effectiveness of face shields alone as well as face masks with exhalation valves.
According to the FAU News Desk, researchers at FAU’s College of Engineering and Computer Science “used qualitative visualizations to test how face shields and masks with valves perform in impeding the spread of aerosol-sized droplets. Widespread public use of these alternatives to regular masks could potentially have an adverse effect on mitigation efforts.”
The study involved a simulation in a laboratory setting using a laser light sheet and a mixture of distilled water and glycerin to generate the synthetic fog that made up the content of a cough-jet. Additionally researchers used a mannequin as the test subject, while simulating coughing and sneezing to mimic human moisture expulsion.
Subsequently, by placing a plastic face shield and an N95-rated face mask with a valve on the mannequin, they were able to demonstrate how both masks blocked moisture from exhalation.
“From this latest study, we were able to observe that face shields are able to block the initial forward motion of the exhaled jet, however, aerosolized droplets expelled with the jet are able to move around the visor with relative ease,” stated Manhar Dhanak, Ph.D., department chair, professor, and director of SeaTech. “Over time, these droplets can disperse over a wide area in both lateral and longitudinal directions, albeit with decreasing droplet concentration.”
To simulate the performance of the face shield, researchers used a horizontal laser sheet in addition to a vertical laser sheet revealing how the moisture moves horizontally. Researchers noted that not only do the droplets spread forward, but they also spread in a reverse direction.
Consequently, face shields hinder forward motion of the exhaled droplets to some extent, and masks with valves do so even less effectively. However, once released into the environment, the small moisture droplets spread widely depending on the environmental circumstances.
Siddhartha Verma, Ph.D., lead author and an assistant professor says, “There is an increasing trend of people substituting regular cloth or surgical masks with clear plastic face shields as well as using masks that are equipped with exhalation valves. A driving factor for this increased adoption is better comfort compared to regular masks. However, face shields have noticeable gaps along the bottom and the sides, and masks with exhalation ports include a one-way valve which restricts airflow when breathing in, but allows free outflow of air. The inhaled air gets filtered through the mask material, but the exhaled breath passes through the valve unfiltered.”
Regardless of the comfortability that these alternative face coverings offer, researchers note that surgical or high quality cloth masks may be better equipped to prevent the spread of COVID-19.
