Scientists at Florida Atlantic University Warn of Failure of Face Shields and N95 Face Shields as Methods to Prevent Spread of Coronavirus.
A study conducted by researchers from the Florida Atlantic University (FAU) College of Engineering and Computer Science found that neither face masks nor N95 valve masks (also called “selfish masks”) are effective in preventing the spread of Covid-19.
The study was published on September 1 in the journal Physics of Fluids and used laser lighting as well as a mixture of distilled water and glycerin to recreate the aerosol droplets that are exhaled when coughing or sneezing and that are mainly responsible for the contagion of Covid-19.
The results obtained in the laboratory showed that the masks are able to effectively block the initial advance of the jet, however this is not enough to prevent the spread of the virus, since the expelled drops move around the visor with relative ease and spread over a large area depending on the environmental conditions.
Over time, these droplets can be dispersed over a large area in lateral and longitudinal direction, albeit with a droplet concentration diminishing, “said Manhar Dhanak, director of SeaTech and coauthor of the study, about the masks.
As for the face mask equipped with an exhalation valve, the trials showed that a large number of unfiltered droplets passed through the mask, making its ability to contain the virus questionable.
The researchers warn that these two types of protections are not useful to prevent the spread of Covid-19, so they call on the population not to trust them as the only prevention measure.
In the United States, “we are seeing a growing trend for people to substitute cloth or normal surgical masks for clear plastic screens or masks with exhalation valves,” said Siddhartha Verma, lead author and professor in the Department of Oceanic and Mechanical Engineering of the FAU.
He added that masks or face shields have holes along the bottom and sides that allow particles to escape, while masks with valves allow air to escape freely.