With the Omicron variant, N95 or equivalent masks are needed to stop infection, according to epidemiologists

Centers for Disease Control and Prevention photo shows a green N95 mask.

The Omicron variant of the coronavirus “spreads much more quickly than its predecessors” and research “suggests the virus has acquired the ability to gain a foothold regardless of a person’s vaccination status,” so epidemiologists recommend you start using an N95 mask or an equivalent, Sandra Guiterrez writes for Popular Science.

“The fibers in a cloth mask are just not dense enough to filter out a large number of particles in the air that may contain Covid-19,” Guiterrez reports. “Then there are surgical masks, which are good at protecting people against infection but not in the way you might think. They protect others if you’re infected because they block your exhaled aerosols from traveling as far as they would without a mask in the way—they don’t protect the wearer as much. . . . The gaps between a surgical mask and your skin make them unsuitable for the level of infectiousness researchers have seen with the Omicron variant.”

N95s have three layers of polypropylene, and the middle layer has an electrostatic charge that allows it to filter out 95 percent of particles, giving the mask its name. “While N95s are widely considered the golden standard for particle filtration, there are other masks that do an equally good job, such as the KF94, FPP1, FPP2, and FPP3,” Guiterrez reports. “The only difference among them is their country of origin. N95s are manufactured under a strict U.S. protocol that is regulated and certified by the National Institute of Occupational Safety and Health.”

The KF94 mask is South Korea’s version of the N95, while FPP masks are the standard in the European Union. “These types are also subject to careful government oversight and perform with similar efficacy to N95s,” Guiterrez notes. They will provide equal protection against Covid-19.”

The most widely available foreign-made mask in the U.S. is the KN95, made under a Chinese protocol. Guiterrez reports that it doesn’t fit as snugly as the other masks, because it has a vertical fold or hinge, which “tend to slide up and down, preventing a proper seal and forcing wearers to touch it constantly to readjust.”
Also, “In September 2020, the Emergency Care Research Institute found that 70 percent of KN95 masks didn’t meet minimum U.S. standards,” Guiterrez notes. “The Centers for Disease Control and Prevention’s website warns that 60 percent of KN95s in the US are actually counterfeit. . . . There’s no way to be sure if they are actually protecting you or anyone around you.”

The CDC website offers guidance for identifying fakes, and has an online search platform where you can see if a brand/model has been certified by NIOSH. Appendix A of Food and Drug Administration list also shows brands and products approved for emergency use.

Guiterrez also cites advice to look for a mask with head straps instead of ear loops: “This feature helps provide that much-needed seal while making it comfortable to wear your mask for prolonged periods of time.”
For many people, the biggest downside of N95 masks is that they are designed for only two to three hours of use. “If you have to regularly interact with someone who’s infected with Covid-19, experts recommend you change your mask every time you come into contact with them,” Guiterrez reports.

However, the masks can be rotated. Peter Tsai, the inventor of the material used to make N95s, suggested in a study back in May 2020 that people use four masks — wearing one while the others undergo decontamination in separate paper bags at room temperature for three days, “enough time for any traces of the virus on the mask to die out,” Guiterrez writes.

 “If you want to be extra careful, you can increase the number of masks in rotation and, say, have one for each day of the week. For this method to work, it’s crucial to identify each mask—you can use a number or color system—to avoid errors, and use a clean paper bag every time you start the decontamination phase.”

Getting rid of the virus “doesn’t mean the mask is clean,” Guiterrez cautions. “There are countless pathogens living in our mouths and airways—not to mention bits of decomposing food—and these also get stuck in our masks every time we breathe out, eat, or talk. . . . If you’re not bothered by weeks-old bacteria living in your mask, or think this is a small price to pay to keep plastic out of the landfill, rotating your N95s is a reasonably safe way to protect yourself and others against Covid-19.”

Also, “you cannot rotate masks forever,” Guiterrez reports. “Wearing your mask day in and day out will eventually affect its ability to do its job. Learning how to spot signs of degradation will help you know when it’s time to get rid of it. . . . As soon as the noseband starts bouncing back and is no longer able to stay in place, or the elastics don’t provide as much tension as they used to, throw your N95 away.” One signal: If you wear glasses and they fog up, you need a tighter mask.
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