Study: Face Shields Not A Good Mask Substitute 〈Tested – Method〉

The Centers for Disease Control and Prevention (CDC) and other health authorities do not recommend face shields as a primary substitute for cloth face coverings because they lack a peripheral seal.

In laboratory simulations, face shields blocked only 2% of exhaled cough aerosols, whereas N95 respirators blocked 99% and medical masks blocked 59%. Comparison: Face Shields vs. Masks Study: Face Shields Not a Good Mask Substitute

While shields block the initial forward "jet" of a cough or sneeze, smaller aerosolized droplets can easily flow around the sides and bottom of the visor. The Centers for Disease Control and Prevention (CDC)