Along with social distancing and frequent hand washing, mask wearing is one of our best defenses against COVID-19. But as the Mayo Clinic warns, not all masks are created equal, and some can be downright dangerous. In a policy posted on its website, the Mayo Clinic has outlined which mask types are welcome on clinic grounds, and which are banned. Among their list of "acceptable masks" are homemade masks that cover the nose and mouth and surgical or procedural masks. The one mask type explicitly branded as "unacceptable" on the Mayo Clinic's list? Any mask with vents.
Their reasoning is simple. While vented masks may help keep particles away from the wearer, "masks with vents or exhalation valves allow unfiltered exhaled air to escape," they explain.
The Centers for Disease Control and Prevention (CDC) has issued a similar warning, and has included vented masks on their own list of masks to avoid. The agency explains that "this type of mask may not prevent you from spreading COVID-19 to others. The hole in the material may allow your respiratory droplets to escape."
As it turns out, that's putting it lightly. To illustrate just how flawed these masks are, Matthew Staymates, a research engineer with the National Institute of Standards and Technology (NIST), created a series of videos comparing vented and non-vented masks. Using an imaging system that "causes differences in air density to show up on camera as patterns of shadow and light," the videos demonstrate how large quantities of unfiltered air exit vented masks.
"When you compare the videos side by side, the difference is striking," Staymates said. "These videos show how the valves allow air to leave the mask without filtering it, which defeats the purpose of the mask."
In short, if your aim is to stop the spread of COVID-19 and keep not only yourself but others safe, it's time to nix valved masks from your PPE rotation. Read on for more mask types that are putting you and others at risk, and for more essential mask news, check out The White House Just Mandated Masks in These 5 Places.
Masks with one layer
According to the CDC, any mask you choose should include either two or three layers. Research has shown that single-layer masks fail to protect you and those around you. One study published in the medical journal BMJ found that "home-made cloth face masks likely need a minimum of two layers, and preferably three, to prevent the dispersal of viral droplets from the nose and mouth that are associated with the spread of COVID-19." And for more masks to avoid, check out The CDC Warns Against Using These 6 Face Masks.
Knit or loosely woven masks
Choosing a mask that's made with a tightly knit material is essential for safety, the CDC says. Not sure if your own mask makes the cut? The CDC suggests holding it up to a light source to see if any visible light passes through it. If so, you should toss your mask in favor of higher quality materials.
In the absence of medical grade protective equipment like a surgical mask, experts suggest using fabric masks that use quilting cotton, silk, or even an added layer of nylon. "For minimizing the chances of transmission, it is important to use masks made of good quality, tightly woven fabric, as well as mask designs that provide a good seal along the edges without being uncomfortable," Siddhartha Verma, PhD, the lead author on an influential study of mask efficacy, recently told Healthline. And for more regular COVID updates, sign up for our daily newsletter.
Scarves or ski masks
The CDC also warns against masks that are actually scarves, ski masks, or balaclavas, which do little to protect against COVID-19. "Scarves and other headwear such as ski masks and balaclavas used for warmth are usually made of loosely knit fabrics that are not suitable for use as masks to prevent COVID-19 transmission," says the health agency. Instead, the CDC recommends wearing these items for warmth over a more protective mask. And for more essential mask guidance, check out The FDA Issued a Warning Against This Kind of Face Mask.
Masks that do not fit properly
Finally, finding a properly fitting mask is crucial to ensuring your safety, as well as the safety of others. According to the CDC's recommendations, an effective mask fits "snugly around the nose and chin with no large gaps around the sides of the face." Beyond the obvious drawbacks of a mask that leaves air gaps for droplets or aerosolized particles to travel through, experts warn that ill-fitting masks require more manual adjustments. The more you touch your face, the more likely you are to spread COVID via contaminated touch. And for more on ineffective face coverings, check out This Type of Face Mask Isn't Protecting You From COVID, WHO Warns.