Risk of infection despite the mask when sneezing and coughing

Everyday masks do not protect 100 percent against infection with the coronavirus. As the authors of a US study emphasize, distances are essential, even with mouth and nose protection. But there are also exceptions

Anyone who sneezes or coughs from a short distance runs the risk of contracting the coronavirus despite face and nose masks. This was the result of a study by American scientists with five different masks. Only a special particle mask offered one hundred percent protection against droplets with virus particles in the test. The study by a group led by Krishna Kota from New Mexico State University in Las Cruces (USA) is in the specialist magazine Physics of Fluids published.

Masks are no obstacle for the smallest droplets

"A mask definitely helps. But when people are very close together, there's still a chance the virus could spread or get sick," Kota said. The researchers built an apparatus in which they sprayed the tested masks with 40,000 droplets (for a sneeze) or 3,000 droplets (for a cough) at a distance of 1.83 meters. The speed in the middle of the droplet cloud was 11.5 kilometers per hour.

A two-layer fabric mask let 3.6 percent of the droplets through. As shown in previous studies, a sneeze can contain up to 200 million virus particles. In such a case, more than seven million virus particles would come through the mask, which is far more than the number of 1,000 particles that, according to previous findings, can be sufficient for an infection with the coronavirus. With a two-layer fabric mask with a filter for fine dust (PM 2.5), 1.7 percent of the droplets came through.

Keep the distances

Only the N95 mask, which meets a standard of the American Federal Agency for Occupational Health Research Niosh, filtered all the droplets out of the air. However, this only applies if someone else sneezes or coughs. If the mask wearer is the source of the cloud of droplets, 0.98 percent of the droplets can penetrate the N95 mask. The surgical mask (0.19 percent) and the masks with fine dust filter (0.19 percent) offer better protection here.

"It's not just masks that help. It's both the masks and the keeping your distance," emphasizes Kota. Their study confirms quantitatively that wearing masks and keeping your distance in most cases offer good protection against infection with the coronavirus, the researchers write. The researchers did not investigate the permeability of the masks without sneezing and coughing or the possible escape of the virus sideways.