Suggestions for Comfortable and Effective Face Masks, e.g. Korean KF94’s

With Covid cases and deaths surging despite widespread vaccinations, face masks are back in. Back when the pandemic first hit in early-mid 2020, all commercial masks of any kind were allocated to medics/first responders. Back then, the only mask option for the rest of us was to cobble together something made of regular cloth. But studies I looked at show that the protective performance of those cloth masks, and even standard rectangular surgical masks, is quite poor [1], compared to the KN95 and similar masks which are now available to the public.

The Delta variant of Covid has certain mutations which cause it to bind more strongly to human cells and hence multiply much faster than the original strain of Covid-19. The death toll in the U.S. alone is now over 1200 per day (which is a really big number, if you think about it) and rising, while other national economies are starting to feel the effects of new lockdowns. The vast majority of hospitalizations and deaths now are occurring among those who have not been vaccinated. Nevertheless, vaccinated people may be potent in spreading Covid. The reason is that the virus multiplies wildly during the first few days of infection, before the body’s immune reaction kicks in and starts to kill off the virus. A study by Coleman, et al. found that singing and talking generally produced much more Covid-laden aerosols than simply breathing, but also that Covid aerosol production seemed to really spike at around day 3 of illness, which is usually well before any symptoms are noticeable.

A cloth or surgical mask is probably better than nothing, but is much inferior to other mask options which are now widely available. If you are going to bother with a mask at all, why not use a more effective one? A well-known effective mask is the KN-95. It has a kind of aggressive beak-like profile, as shown below, and typically uses elastic earloops. It gives good protection because it seals to the face (including around the nose, thanks to a malleable metal strip there) and is made of appropriate multi-layer filter materials. It is the standard protective respiratory mask in China, whereas in the U.S. the standard protective mask is the the thicker, more-rigid “N95”, with elastic straps that go around the whole head, not the ears.

Image Source: Amazon

I got a box of ten KF95’s back in June of 2020. I loved them – they were comfortable, worked OK with my glasses, and clearly sealed well to my face. However, I gave some of these away to family members, lost a few, and used the rest so many times so they started to lose their shapes.

There are lots of KN95’s for sale on Amazon, all made in China. Not all of these may be of the same quality. Some but not all of these brands were tested and approved by the FDA for emergency use; this article from March 2021 notes some of these brands that were for sale on Amazon at that time. It seems the approved Powecom masks are still for sale.

A problem with most of these Amazon KN95’s is that the earloops are painfully tight around the ears. I pored over the comments to try to select masks where at least some of the reviewers claimed the masks didn’t hurt. Alas, all my new KF95’s are pretty much unbearable for a guy like me with maybe an oversized head. (I compared the length of their earloops with my original comfortable KF95, and indeed the earloops are clearly shorter on all the new ones).

In the course of reading dozens of reviews of KN95 masks, I saw several comments recommending KF94 masks instead. These are made in South Korea. They are standard personal protective equipment in that country, and as such must meet certain standards for fine particle capture. They look a little different than most masks, but seem less beak-like than the KN95s. They have a flattish rectangular middle part which is the main filter, with two triangular sections that cover the nose and the chin:

Image: Amazon

So I got a box of KF94’s, large size, and they are wonderfully comfortable for me. No stress on the ears, and sealing over the whole face. The shape of the mask keeps it from rubbing on your mouth. The “Large” size I got was actually a tiny bit looser than felt optimal, so I tied tiny knots in the lower part of the earloops to shorten them a bit. My wife uses a mask extender strap (e.g., HX AURIZE Mask Extender Strap on Amazon) around the back of her head to pull the KF94 earloops a little tighter, with the added benefit that if she wants to take the mask off temporarily, it can hang around her neck via the extender strap. In sum, the KF94s are a win, and I highly recommend them.

I see on Amazon that small (for e.g. 7-12 year old children) and medium KF94 masks are also available. One caveat on buying is to make sure that you are buying from an actual Korean seller, else you risk getting an inferior Chinese knockoff.

Back to my unusable KN95’s. I know that you can use mask extender straps like the HX Aurize straps linked above, or similar homemade hacks, to go behind your head and take some of the direct pressure off the back of the ears. However, I found using a behind-the-head strap still put pressure on part of my ears, and was just an added complication. I thought, surely there must be some way to make those darned earloops simply longer. What I did for one mask was to cut the earloops close to the bottom of the mask, and tie in a small rubber band into each loop, to make them effectively longer. (I put a dab of glue on the cut ends of the earloops, to keep them from unravelling). That worked out well, so I can recommend this as a “hack”. I also see on Amazon that you can order ¼” wide white elastic ear loop type band material, and I think I will buy some. I can then take more of my tight KN95 masks, cut the existing earloops, and tie in an extra inch or two of this elastic to get the length right for my head size.

(This just in: per comment sent in by Chris Falter, comfortable KN95’s with elastic loops which go around the whole head, not just the ears, are available here at The whole-head straps press the mask against the face more firmly than earloops can. Bonafidemasks also carries U.S. standard N95 masks.)


If you have to wear a mask in some hot environment such as working in a warehouse or attic, any kind of mask is a pain because your breath heats and moistens the mask and so what you breath in gets hotter and hotter. A device for this situation that gets good reviews on Amazon is a little fan-driven external filter you wear around your neck which pulls in fresh outside air, pushes it through a HEPA filter, then delivers this via a hose to inside your KN95 mask. You are always breathing in fresh, cooler outside air, instead of heated wet air through your mask. This gadget should protect you from other people, but has the significant downside that it will no longer protect other people from any infection you have, since excess air pumped into your mask may leak out around it, carrying out some of your breathed-out air.


Political hackles rise on the left and on the right when the subject of mask mandates is raised. Besides the discomfort and inconvenience of wearing masks, concerns have been expressed over the psychological/social effects, particularly on children, of having facial expressions largely hidden, when Covid infection among children and teens is typically found to be only a tiny risk factor compared to other causes of death in that age group. I have no new insights to offer on all that.

However, if it is deemed necessary to mask up, I’d suggest that the policy debate include what types of masks should be included. Why not use masks that are known to do a much better job at protecting from the spread of viruses like Covid? If you have the misfortune of being in a room where someone is talking and inadvertently filling the air with invisible Covid aerosols, would you want 50% protection or 95% protection? Is it just the cost or are there considerations of style or some subtle politics (I simply don’t know)? The good masks are not washable and are not reusable indefinitely, but if you have two or three of them, you can let each mask dry out for a day or two after each use to keep bacteria from getting hold.

KN95s from China and KF94s from Korea are now available in large quantities for less than $2.00 apiece, and surely America and Europe could produce massive quantities of such masks if there were the slightest political will to do so. (No one has explained to me why the West didn’t appear to make much effort to produce such masks either in early-mid 2020 when not even the Asian masks were available, or now after the fragility of global supply chains has been exposed – -but I guess that is another subject for another time).


[1] Some studies on masks:

(A)  Kim, et al. 2020. They had seven Covid-inflected patients cough five times with various masks on, and with petri dish sitting in front of them to catch germs. A surgical mask did no better than no mask at all (3 out of 7 patients’ petri dishes got infected in both cases), whereas zero out of 7 patients’ petri dishes got infected for a full N95 respirator made by 3M (not a Chinese KN95) or for a Korean-made KF94 mask.

(B)   Bundgaard, et al., 2020. Done in Denmark around April-June 2020. From 6000 participants, all of whom initially tested Covid-negative, half were randomly selected to wear standard surgical-type masks while in public and half to not wear masks. (These are the usual rectangular masks that do not seal tightly to the face). Incidence of Covid infection after about a month was assessed for each group. For mask-wearers, the infection rate was about 1.8% versus 2.1% for the non-masked group. According to standard statistical definitions, this was not enough to conclude that wearing that type of mask gave “significant” protection against becoming infected. That said, the difference between the 1.8% and the 2.1% is compatible with a 46% reduction to a 23% increase in infection using 95% confidence intervals. Depending on how you want to slice the numbers, it seems fair to say that there may have been “some” effect of the masks here. Also, it should be noted that this study tested whether masking could protect a healthy person from getting sick, but it did not test whether wearing a surgical mask would help keep an infected person from spreading the disease (I suspect there may have been more of an effect there, but realistically if someone were *known* to be infectious, no responsible study would have them running around in public with or without masks).

(C) Ueki, et al., 2020. They used two full size human mannequin heads, and tied masks on their faces. The “Spreader” head was piped to have a stream of covid-aerosol-laden air coming out of its mouth. The “Receiver” head had a pipe that pulled air in through its mouth and through a gelatin membrane filter to collect the covid viruses that made it through the masks. Some of the results are shown below. I am not sure how to summarize them accurately in a few words. Note that these plots are on log scales, so small visual differences in the bars are actually big (see the numbers at the bottom of the bars). It seems clear that the cloth (cotton) and the surgical masks blocked some virus spreading compared to no masks, but a full N95 mask was much more effective (the N95 was tested with its edges naturally resting on the contours of the mannequin face, and also “fit” with the edges sealed against the face with adhesive tape). A KN95 or KF94 mask was not tested here.

( D) The effectiveness of masks depends on two main factors. One is how well the mask seals to the face (lest air simply bypass the mask altogether). There is obviously a big difference between cloth or surgical masks which fit loosely on the fact, versus N95/KN95/KF94 masks which seal fairly tightly to the face, and have a malleable metal bar which molds around the nose. The other factor is how well the mask material traps viral aerosol particles as breathed air is forced through the material.

In a 2021 study by Lee, et al., Mask material was clamped between two flanges, and contaminated air was forced through the mask material. In this arrangement, there was no leakage around the mask material. Fine dust and a bacteria-containing bioaerosol were used to test the filtering ability of four types of mask material: woven cloth (typical of the popular cotton or polyester cloth face masks), nonwoven flat rectangular surgical type masks, and two Korean filter mask types, namely KF80, and KF94 masks. These two types are fairly similar except the KF94 are certified to be more efficient at filtering out fine particles than are the KF80’s. Four different brands or models of each of the four mask types was tested. As might be expected, the KF94’s gave the best filtration performance, followed by the KF80 and surgical masks (close to each other), while the woven cloth gave significantly poorer filtration performance. This paper references a number of prior studies showing high penetration of aerosols through cloth masks.

(E) A survey of research by Jeffrey Anderson (August, 2020) summarized many real-life randomized controlled trials with populations wearing/not-wearing masks (presumably the surgical kind, not N95/KN95/KF94 better-sealing types) which found generally no benefit to the public wearing these types of  masks in reducing the incidence of virus transmission. (These studies were mainly pre-Covid, dealing with SARS and other viruses). This overall result is roughly consistent with the Danish study mentioned above, which did not find a significant difference for using those types of masks for Covid.

(F) See comment below by Chris Falter, and my response, re recent mask study in Bangladesh.

G) A study by Asadi, et al. (2020) was done where volunteers wore various types of masks and breathed/talked/coughed and the total amount of aerosol particulates was measured. A well-fitted high-end surgical mask (nose piece shaped around nose, and outer part of mask seemed to seal closely to skin due to generous pleats in mask) and a KN95 mask gave significantly less particulates for talking and coughing than no mask. Interestingly, the surgical mask seemed even more effective than the KN95. Various homemade cloth or paper towel masks did not seem to give a decrease in particulates, but maybe that is because the mask material itself gave off some particulates.

About Scott Buchanan

Ph D chemical engineer, interested in intersection of science with my evangelical Christian faith. This intersection includes creation(ism) and miracles. I also write on random topics of interest, such as economics, theology, folding scooters, and composting toilets, at . Background: B.A. in Near Eastern Studies, a year at seminary and a year working as a plumber and a lab technician. Then a B.S.E. and a Ph.D. in chemical engineering. Since then, conducted research in an industrial laboratory. Published a number of papers on heterogeneous catalysis, and an inventor on over 100 U.S. patents in diverse technical areas. Now retired and repurposed as a grandparent.
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2 Responses to Suggestions for Comfortable and Effective Face Masks, e.g. Korean KF94’s

  1. Chris Falter says:

    Good, helpful post! If your post causes a run on KF94 masks that wipes out the supply, I can suggest an alternative: My wife and I have been using comfortable, Powecom KN95 masks that have wrap-around straps. We get them from bonafidemasks(dot)com. I am a data scientist that works for a consulting firm in northern VA, and I have no affiliation with the vendor other than that I am a satisfied purchaser of their KN95 masks.

    Also, Yale economists Jason Abaluck and Mushfiq Mobarak announced just today a preprint of a massive, long-duration random control trial of surgical mask wearing in Bangladesh. The results show a strong effect of the intervention for preventing COVID-19 infection and symptoms.

    A nice, journalistic synopsis is here:

    The preprint is available here:

    • Chris, thanks for the info on good KN95’s and on the Bangladesh study.

      It is encouraging that some effects of the masking in public were observed in that study, but they were still pretty modest. It amounted to a 1% drop in infections (from 7.6% to 8.6% COVID-like symptoms in the “intervention” [more-masked] vs. control populations) or about a 10% relative drop in infections. Some portion of that drop may also be due to the practice of more rigorous social distancing in the intervention population. On the other hand, this was not a 0% vs. 100% masked experiment like the Danish study – – public mask-wearing was estimated (from field observations) as 42.3% in the Bangladesh intervention group vs. 13.3% in the control population. Presumably a 0% vs. 100% test would have given stronger results for masking.

      All that said – – if we are going to mask up, it seems there is a case to be made for using more-effective masks as opposed to any old rag.

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