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Frank Bures: What's in a mask? Differences between N95, KN95 and other masks

Frank Bures: What's in a mask? Differences between N95, KN95 and other masks

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At the end of July, the CDC made new mask recommendations for mask wearing because lots more people were getting infected, going to the hospital, and dying from COVID-19. In general, they are saying to mask up indoors in public places, especially in areas where cases are increasing. They also have said all teachers, staff, students, and visitors should mask up in schools. One headline on a recent article was “mask-to-school time.” So, what is the best choice of mask for protection?

The gold standard in the U.S. for medical settings is the N95 mask. But KN95 masks are also advertised. The K represents Chinese-certified masks. Other choices are the typically blue pleated surgical masks and cloth masks. Production of the latter in the early pandemic days became a true cottage industry. The N and KN95 ones have a high filtration rate of particles from the air and a very snug fit. They are labeled respirators because you must breathe through them, not around at the edges like you do with the looser fitting cloth and surgical ones.

N95 masks are tested and approved for medical personnel use by the National Institute for Occupational Safety and Health (NIOSH), which is part of the CDC. The KN95s are from China, and tested and approved to different standards by a similar government agency there. They are both made of tough but flexible polypropylene fibers about 5 layers thick with a pore size of 0.3 microns. They both filter out about 95% of particulate matter 0.3 or larger, and even smaller.

N95s can filter out about 99.8% of particles 0.1 microns in diameter per a 2017 study. The SARS-CoV-2 virus is about 0.1 microns wide and often is hooked water vapor particles that increase its diameter. The particles smaller than 0.3 wander into a N95 mask and wind up moving in a zigzag pattern to get trapped on the fibers. Plus, the masks use electrostatic absorption, which helps trap the particles. The same conditions apply to KN95s. Reuse of any mask is another topic.

N95s have head straps, which help the seal be snugger, while KN95s have ear loops. The testing differences revolve around N95s undergoing a “breathability” testing, which makes them easier to breathe or respire through than the KN95s. KN95s, on the other hand, do undergo testing for facial sealing at edges on human faces, which assures their fit. Because of the desperate shortage of personal protective equipment (PPE) at the beginning of the pandemic, the CDC authorized substitution with KN95s as suitable.

Surgical masks made with 3 layers can do a pretty good job of blocking floating microscopic germs, but in an ICU or operating room closed space that leakage becomes crucial. The discussion was brought up in several references about fake or counterfeit masks that come nowhere near 95% filtration. The N95s do have a NIOSH approval stamped on them.

Other countries make and test their own masks. The KF94 comes from Korea, and means Korean Filter with 94% efficiency. Others are Europe (FFP2), Australia, (P2), and Japan (DS). For common daily purposes these are pretty much equivalent. Surgical masks are made to be fluid resistant to protect against large droplets, splashes or sprays of body (NOT bodily) fluids as in surgeries. Dr. Fauci has recently recommended double surgical masking as greater protection.

Cloth masks filter the least particles, but are better than no mask, period. One home sewn model we obtained had two layers and a filter in the middle. One like that could be considered.

The contentious argument whether to wear a mask at all or not is completely political, and disregards the reality of the microbial world we live in, with the literally millions of microbes we encounter daily. When the bad ones come to town, we need to use all of our weapons to combat them as long as these current viral varmints are swirling and swarming around us. This is especially true in close and crowded quarters, like schools. Today it was reported there have over 1,400 school closures across the country in the last few days. 250, 000 children are known to be infected recently. The viruses don’t seem to be going away soon.

Should you wear a mask in public places? Why not? Every little bit helps both you and the entire community to avoid infections. The longer the viruses are allowed to incubate in us humans, the more mutations and variants will emerge to prolong this mess. Consider wearing an N95 or KN95 type mask and give your face a “seal of approval.” For those of us who wear glasses it lessens the fogging. I’ll close with someone else’s quote: those who wear glasses and a mask are entitled to “condensation.”

Dr. Bures, a semi-retired dermatologist, since 1978 has worked Winona, La Crosse, Viroqua, and Red Wing. He also plays clarinet in the Winona Municipal Band and a couple dixieland groups. And he does enjoy a good pun.


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