How Well Does One-Way Masking Protect You From COVID?

Mask mandates have largely been lifted across the country for indoor places, planes, and public transit. But the striking down of mandates leaves immunocompromised people and unvaccinated individuals, like kids, vulnerable to infection.

Many are continuing to “one-way mask”: wearing a face covering when others around them aren’t, despite lifted restrictions. But how much can one-way masking protect you?

Choose High-Quality, Well-Fitting Masks

Experts say its effectiveness depends on a few factors, like the type of mask you're wearing.

“The type of mask you wear, especially in a one-way masking scenario, makes a difference,” Vincent Hsu, MD, executive director of infection prevention at AdventHealth Orlando, told Verywell. “Wearing a well-fitted mask such as an N95 or KN95 is more effective than a cloth or surgical mask, but wearing any quality mask is better than none.”

Currently, the BA.2 variant still accounts for the majority of COVID-19 cases in the country, but the number of infections caused by the Omicron BA.2.12.1 subvariant is steadily growing every week.

The more transmissible variants of COVID-19 have mutations that make the virus bind even more tightly to receptors on cells, such as those in the nasopharynx, so being exposed to fewer viral particles may still lead to an infection, Stanley H. Weiss, MD, a professor of medicine at the Rutgers New Jersey Medical School and professor of biostatistics and epidemiology at the Rutgers School of Public Health, told Verywell.

To protect against these mutations, you’ll need a higher level of protective gear, which is why he recommends well-fitting, high-quality N95 or KN95 masks.

“Both the type of mask and fit are very important,” Weiss said. “Even short exposure time without these can lead to viral acquisition. Covering the nose well is critical—yet many people let their mask slip below the now or fail to get an excellent fit around the nose, putting themselves at high risk.”

The CDC’s mask guidance specifies that the mask must cover the nose and mouth, fit under the chin, and feel snug on the face. There are plenty of ways to improve the fit, such as wearing a cloth mask on top of a surgical mask or using mask fitters.

The Risk of One-Way Masking Situations

Although masks work best and provide the most protection when everyone is wearing them, they are still effective even if you’re the only one masking. But different situations pose varying levels of risk.

Transportation

The ventilation of a mode of transportation plays a role in how much risk it poses to its passengers.

Within any closed environment—including vehicles—the speed of air exchange is important for diluting contaminated air. If the person sitting nearby is wearing a well-fitted mask, the chance of releasing infectious particles is tremendously reduced, Weiss said.

“Not all modes of transportation have similar ventilation capacities, but most commercial aircraft have high levels of ventilation, thus making transmission much less likely from passengers seated away from you,” Hsu said.

Although the HEPA filtration systems that airplanes use do not completely eliminate the risk of virus transmission aboard flights, they remain highly effective at reducing it. So one-way masking may be more effective on a plane than it might be in another type of vehicle.

For instance, buses and trains tend to be more crowded and poorly ventilated, Chris Beyrer, MD, MPH, an epidemiologist at the Johns Hopkins Bloomberg School of Public Health, told Verywell. When it comes to one-way masking, the key factors are community transmission, rates of vaccination, crowding, and ventilation, he added.

Indoor Venues

Indoor spaces are far riskier than outdoor spaces because it’s more difficult to keep people apart and there’s usually less ventilation. The air exchange rates of restaurants, schools, and other indoor places are likely still limited unless their HVAC systems have been revamped, Weiss said. Therefore, one-way masking poses a high risk.

Many now recognize the importance of ventilation in buildings and are working to upgrade their systems, Hsu said. “Crowded restaurants remain a higher risk than other indoor venues due to the fact that you can’t wear a mask when you eat,” he added.

A 2021 preprint study posted at DepositOnce found that going to museums, theaters, and operas is far safer than going to other indoor environments if they are kept at 30% capacity and everyone is wearing a mask and following proper precautions. This scenario carried the lowest risk, according to their findings.

Shopping at a supermarket at 80% occupancy while wearing a mask is considered almost twice as risky, and working in a multi-person office at 20% occupancy with a mask on carries about three times the risk. Meanwhile, going to an indoor swimming pool with 100% occupancy or a restaurant with 50% occupancy—where people don’t usually wear masks because they’re swimming or eating—is more than four times as risky as the lowest-risk scenario.

“Recognize the importance that ventilation plays in public areas,” Hsu said. “It is difficult to know how well ventilated an enclosed space is, but we recognize good ventilation and air circulation play a crucial role in diluting the effectiveness of virus transmission.”

Outdoor Places

The outdoors carry a much lower risk and masking is rarely recommended, Beyrer said. Even without wearing masks, individuals are less likely to be exposed to COVID-19 outdoors, according to the CDC.

Compared to indoor activities, outdoor recreation such as hiking, kayaking, fishing, or biking are likely much safer. However, outdoor activities are still affected by increasing levels of community transmission, depending upon how close you are to others, Hsu said.

“Every individual needs to assess their medical conditions and risk of severe disease and will need to make a choice about whether traveling in public places is worth the risk of infection, despite being up to date on vaccines,” he added. “The higher the community transmission levels, the greater the risk.”

Staying Cautious

Although COVID-19 restrictions have loosened significantly over the past few weeks, it’s crucial to remember that there are still thousands of Americans who get infected by the virus every day. Unvaccinated and at-risk people remain at risk for severe outcomes. 

“The BA.2 and its sub-variants are highly infectious in the days before symptoms, when someone is still asymptomatic, and thus can unknowingly pass it on,” Weiss said. “At least some people remain infectious five days after initial symptoms, and this proportion may be higher than seen in other variants. Thus, the risk of passing it on is higher than in the past, and it is now harder to feel safe just because those around you seem well.”

Aside from watching the variant that is currently circulating in your area, it’s also important to be consider the incidence of COVID-19 among the people you're going to be exposed to.

For instance, people on various forms of transportation may come from a place with a rising incidence of infections, therefore the risk that they pose can be much higher than what you’d expect based on the community transmission of your local area alone, Weiss added.

Ultimately, spending a greater amount of time in a public place will increase the risk of transmission, Hsu said. It can be difficult to gauge the potential risks of a given activity—especially when you can’t be sure that other people will be wearing masks. So to increase your protection against COVID-19, make sure you are up to date with your COVID-19 vaccination.

“The best protection is being vaccinated and boosted,” Beyrer said. “Adding a mask further reduces risks, but not completely, since Omicron and its new subvariants are so much more infectious than earlier variants of the virus.”

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.