Amid a slow vaccine rollout and expanding reports of a highly contagious new variant of the COVID-19 virus, masks are increasingly recognized as a critical tool in slowing the pandemic.

But how do you choose? One year into the pandemic, there are still no filtration standards or labeling requirements. Masks range from hospital-caliber N95s to silky Mickey Mouse gaiters.  They may not fit. They may filter poorly.

“It’s really the Wild West out there,” said Joseph Allen, associate professor and director of the Healthy Buildings program at Harvard University’s T.H. Chan School of Public Health.

“We’re a year into this pandemic. It shouldn’t take hours and hours for a consumer to try and figure out what’s a decent mask,” he said.

And while there’s been great innovation in the realms of vaccines, therapeutics and testing, “it’s shocking that we haven’t seen any innovation on the side of this simple and most effective tool.”

But a growing body of research is teaching us more about masks. Here are answers to some of the most commonly asked questions.

Q: What constitutes a good mask?

A: The N95 mask — 95% effective — is the gold standard, but it’s in short supply.

The KF94 mask, the Korean version of an N95 mask, offers high-level protection. These masks are rigorously screened.

KN95 masks are the Chinese equivalent of N95s.  But you need to do your homework to be sure that it’s a mask that has been vetted and verified. Buy it only if the manufacturer holds a “NIOSH Certificate” — that’s from the National Institute for Occupational Safety and Health.

Blue surgical masks are about 70% effective.

A cloth mask may be between 20% to 70% effective, depending on its construction and the fabric that is used.

— Joseph Allen from Harvard University’s T.H. Chan School of Public Health.

Q: What about “double-masking”?

A: The Centers for Disease Control and Prevention has not addressed layering masks.

You might consider layering your face coverings if you are spending time indoors in crowded spaces or in areas where transmission rates are high. People who are medically vulnerable could also consider doubling up.

There are two approaches. One is to wear a tightly fitted, multiple-layer cloth covering over a surgical mask. They other is to wear a three-layer mask with tightly woven fabric outer layers.

— Dr. Monica Gandhi, professor of medicine and an infectious-disease expert at the University of California at San Francisco

Q: What mask is best if I’m just out on a hike or sitting on a park bench?

A: Choose your mask based on the level of risk for that activity. If you’re out for a jog with no one around or on a walk outside with a friend, a simple two- or three-layer cloth mask is fine.

If you’re conversing, the power of masking doubles if both people are wearing them. That’s because the particles have to pass through the material twice — once after being emitted and again before someone breathes them in. Research shows that two masks that are 70% efficient combine to reduce more than 90% of particles. Two N95s result in greater than a 99% reduction in exposure.

— Joseph Allen

Q: How do I test a mask’s fit?

A: The mask needs to go over the bridge of your nose, down around your chin and flush against your cheeks.

Every time you put on a mask, do a “user seal check.” Put your hands over the mask to block the air moving through it, and exhale gently. You shouldn’t feel air coming out the side or up toward your eyes. Then, test to make sure it stays in place by moving your head side to side and all around. Try reading out loud and see if it slides around when you talk.

— Joseph Allen

Q: Why can’t healthcare workers reuse N95 masks?

A: In medical settings, a significant percentage of N95s failed a fit test after four or five “donnings” and “doffings.” They no longer fully sealed the face.

There’s no universal guidance on best practices for disinfecting and reusing N95s. Some research supports sterilizing N95s with bleach. Use of ozone has also been approved by the FDA for some reusable medical devices. But these tactics need further research to ensure safety.

— Get Us PPE, a national organization founded by emergency physicians  in response to urgent PPE shortages.

Q: I keep my mask stored in my car. Is that OK?

A: Yes, but if you have a cloth mask, you want to be washing the mask daily. Hang it up after you’re done using it, because the virus decays or inactivates over time. How long does that take? It’s influenced by the temperature and humidity where it’s stored — but over a day, it’s going to be OK.

— Joseph Allen

Q: Are neck gaiters safe?

A: Gaiters are popular because they are often made of lightweight, breathable material and don’t require ear loops; they conveniently sit on your neck, like a scarf.

A single-layer gaiter, alone, isn’t adequate. But when it is doubled up, it is highly effective at blocking a range of particle sizes. In experiments done by Virginia Tech professor Linsey Marr, a doubled-up gaiter blocked more than 90 percent of the particle sizes tested.

— Linsey Marr, professor of civil and environmental engineering at Virginia Polytechnic Institute and State University

Q: How should I clean my mask?

A: Reusable masks should be washed regularly. Always remove masks correctly and wash your hands after handling or touching a used mask.

Include your mask with your regular laundry. Use regular laundry detergent and the warmest appropriate water setting for the cloth used to make the mask. To dry, use the highest heat setting and leave in the dryer until completely dry.

— CDC

Q: If I’m vaccinated, do I still need to wear a mask?

A: Yes. Although the Moderna and Pfizer/BioNTech mRNA vaccines are more than 94% effective in fending off symptomatic COVID-19, asymptomatic infection could not be ruled out in either trial among vaccine recipients.

Additionally, the duration of vaccine protection is not yet known and widespread vaccination to reach population-level immunity — 60% to 70% — will take some time.

— Monica Gandhi

Q: How could masks be improved?

A: So right now, we have masks that have sufficient filtration — 95% or 94% filtration efficiency is excellent.

But we need masks that fit better, particularly in the bridge around the cheek. There have been some efforts to develop “add-ons” that you would wear on top of a mask to help improve fit, but other innovations are needed.

Probably the most important thing from a consumer perspective, though, is standardization and labeling, to guide the user what should be worn during which activities. This would boost confidence that a mask would meet a minimum performance requirement.

— Joseph Allen