Will a mask protect you from Covid if no one else is wearing it?

If I am the only person wearing a mask in a store or other indoor location, am I truly protected from infection?

It is true that masks work best when everyone in the room is wearing one. This is because when an infected person wears a mask, a large percentage of their exhaled infectious particles are trapped, stopping the viral spread at the source. And when fewer viral particles float around the room, the masks others are wearing would likely block the ones that escaped.

But there is also a lot of evidence showing that masks protect the wearer even when others around them are maskless. The level of protection depends on the quality of the mask and its fit. During an outbreak at a hotel in Switzerland, for example, several employees and a customer who tested positive for the coronavirus wore only face shields (no masks); those who wore masks were not infected. And a study from Tennessee found that communities with mask warrants had lower hospitalization rates than areas where masks were not needed.

“Healthcare workers, scientists who work with dangerous pathogens, and workers who may be exposed to dangerous airborne particles at work rely on specialized masks like N95s to protect themselves, we So know that well-fitting, high-efficacy masks work, ”said Linsey Marr, an engineering professor at Virginia Tech and one of the world’s foremost experts in viral transmission.

A number of laboratory studies have also documented that a mask protects the wearer, although the level of this protection may vary depending on the type of mask, the material it is made of, the experimental setup and how particulate exposure was measured.

But the gist of all the studies is that a mask reduces the potential exposure of the person wearing it. Here are some of the findings.

• A study from the Centers for Disease Control and Prevention found that a standard surgical mask only protected the wearer about 7.5% of particles generated by a sham cough. But tying the buckles and tucking in the sides of the medical mask reduced exposure by almost 65%. (Watch this video to see the “tie and fold” method.) Covering the surgical mask with a fabric mask, a technique known as double masking, reduced exposure to simulated cough particles by 83%.

• A study by Virginia Tech looked at how well homemade masks, surgical masks, and face shields provided wearer protection, based on particle size. Research has shown that most masks can block very large particles, such as those from a sneeze. But when the researchers looked at the smaller aerosol particles that are the most difficult to block, the protection ranged from near zero with a face shield to about 30% protection with a surgical mask. (The study percentages cannot be directly compared to those in the CDC Knots and Folds study because the testing methods were different.) Based on the results, Dr Marr and colleagues concluded that ” a two-layer fabric mask made of a soft, tightly woven fabric, combined with a filter material (such as a coffee filter or surgical mask), could provide good protection, reducing 70 percent of the most penetrating particles and trapping 90 percent or more of the larger particles. They also found that headbands or ties created a better fit than earrings.

• A Tokyo study tested how well different types of masks protected the wearer from real coronavirus particles. The study showed that even a simple cotton mask offered some protection (17-27%) to the wearer. Medical masks performed better, including a surgical mask (47-50% protection), loose N95 (57-86% protection), and hermetically sealed N95 (79-90% protection).

• While many lab studies test masks using mannequin heads, a 2008 study used real people to measure how well masks could protect the wearer against a respiratory virus. The study subjects wore different types of masks equipped with special receptors capable of measuring the concentration of particles on both sides of the masks. In this study, cloth masks reduced exposure by 60%, surgical masks by 76%, and N95 masks by 99%.

Although laboratory studies all show that a mask can protect the wearer, the performance of masks in the real world depends on a number of variables, including how regularly people use them, whether a person is in the area. high-risk situations and the rate of infection. in the community. A Danish study of 6,000 participants, half of whom were asked to wear masks, showed no benefit from wearing masks, but the study was widely criticized for its poor design.

Laboratory studies have shown that a high quality medical mask, such as an N95, KN95 or KF94, works best. Although vaccination is the best protection against Covid-19, even those vaccinated are advised to avoid crowds or large groups indoors when the vaccination status of others is not known. Since the Delta variant is much more contagious than the other variants, Dr. Marr also recommended wearing the highest quality mask possible when you can’t keep your distance or be outside – or when no one is around. of you do not hide.

“If I am in a situation where I have to rely only on my mask for protection – unvaccinated people may be present, there are people, I don’t know anything about ventilation – I would wear the best mask on my guard- dress, which is an N95, ”said Dr. Marr. “Because Delta has been shown to be much more easily transmitted and because people who have been vaccinated can transmit it, we need to wear the best masks possible in high risk situations.”