Some scientists are recommending wearing two masks at the same time to boost protection against the spread of the coronavirus.
While the best masks — N95s, which are typically used by health care workers — remain in short supply, Dr. Linsey Marr is one medical professional who is saying layering other masks may help prevent catching COVID-19.
Marr said that "if you combine multiple layers, you start achieving pretty high efficiencies" of blocking viruses. Marr was one of the authors of a recent commentary on a study about the effects of double-masking on the spread of the coronavirus.
According to the study, masks reduce the spread of the coronavirus because the virus particles cannot navigate the fibers of the masks.
"Filtering is not sieving out things that are too large to pass through holes in the material. Rather, air must curve as it flows around individual, tightly packed fibers of the material, like a race car swerving around cones of an obstacle course," the commentary said. "As the air curves, the aerosols it carries cannot make the sharp bends and therefore slam into the fibers, or they come too close to the fibers and stick to them."
Experiments testing the effectiveness of masks have found that they can be at least 50% effective in either direction.
Marr said that the point is not to make the masks airtight, but to make it more difficult for viruses to penetrate. This can be done by layering two non-specialized masks, such as cloth masks or surgical masks, on top of each other, or to wear a cloth mask that has a pocket for a filter material.
"The air has to follow this tortuous path," Marr said. "The big things it's carrying are not going to be able to follow those twists and turns."