Face Masks: Learn ’em, Live ’em, Love ’em (And for pity’s sake, WEAR THEM!)
April 5th, 2020 by Blaise

Most folks connected with me on social media have only seen the occasional comment or link from me about how the SARS-CoV-2 crisis is being handled in the U.S., but have no idea that I’ve spent the last three weeks working on practical and citizen-available ways to improve the survival rates of our medical personnel and our species (with the permission/support of my employer, General Electric, no less!).

Mask Selfie
Yes, I had to cut my own hair, shut up!

My wife Sabrina and I are among the founders of our local makerspace, the Tech Valley Center Of Gravity, and we are actively involved in numerous ongoing projects with members of that group to produce various types of readily constructed protective and medical equipment to address the lack of availability to medical personnel and people in general. The avenues are numerous, from 3D printed medical faceshields to ventilator parts to n95 mask sterilization chambers to effective cloth facemasks to my personal baby, a positive-pressure, filtered facemask with integrated faceshield (the prototype works, FYI, but I need to do some serious engineering review before trusting someone’s life to it!).

At any rate, unless you are a member of our makerspace’s Facebook group, the little you’ve seen from me on the “Coronavirus” topic has been incidental information I’ve run across as the result of the extensive research I’ve been engaged in pursuant to these projects, but it is by no means indicative of my level of knowledge on some parts of our current predicament. Everything I’ve said so far is a preface to explain that while I am not a doctor, I have accidentally become somewhat expert in a few small areas of the science of protecting individuals from the transmission of disease.

At the beginning of the CoVid-19 crisis, the CDC and NIH made a TERRIBLE mistake for a good reason. The good reason was that as soon as news of the epidemic was widespread, people started hoarding a particularly effective kind of respirator mask called an “N95” mask. These masks are so named by NIOSH because they are Not resistant to oils, and can remove 95% of particles of 0.3 micron diameter and above. This is important, because they are considered the gold standard for protecting medical personnel from infectious disease while treating patients. Therefore, to stem the hoarding of these masks (and surgical masks in general), these agencies fibbed to the American public, telling them that while commercial facemasks were vital and effective for medical personnel, facemasks of any kind did not protect the general public from disease.

This lie was twofold. First, it was false because regardless of the ability of a mask to protect its wearer, facemasks of any kind give significant protection to those in the vicinity of the wearer if they are infected, so widespread use would always have been an effective method of slowing transmission. Second, it was false because there is significant science to support the fact that not only are masks protective to the general public if properly worn, but that even homemade masks can be quite effective in protecting the wearer from infection, if proper procedures are followed.

This lie has resulted in a big chunk of the American public no longer trusting these agencies, because you don’t need a degree to have serious logical objections to the idea that something cannot protect you unless you have the magic of belonging to a particular profession. It also had the effect of making a different big chunk of the American public feel the need to shame people who wore respirator/surgical masks in public. That said, given that the CDC and NIH have officially changed their tune and now recommend that everyone wear masks in public, the main point of this article is not to analyse this failure, but rather to inform on the efficacy of masks in general and the procedures you should follow to use them effectively.

On the topic of commercial mask efficacy, and I hope somewhat heartening for medical professionals, a study from last fall found that there is no statistical difference in effectiveness at preventing viral infection between an N95 mask and a standard surgical facemask. Likewise, a dentist friend who is hooked into some research tells me that in the next (May) journal of the American Dental Association, there will be a research paper published that found that normal ASTM level 3 surgical masks, when fitted properly and used with eye-protection/faceshield, are 98% effective at preventing transmission of SARS-CoV-2 to the wearer in dentist-close quarters with an infected person. As far as I can tell, that is again approximately as good as the estimated transmission rate for an “N95” mask with faceshield. This is very good news overall, as surgical masks are *much* easier to find and cheaper to buy (although still challenging to obtain in the current situation), so medical personnel without access to N95 masks still have a fair chance of being protected with standard masks that are likely much more plentiful in their facilities.

On the topic of home-made/DIY mask efficacy, in 2008, a Dutch study found that found that a simple mask made from common dish-cloth stopped up to 60% of particles in the 0.2 micron range, i.e. the hardest virus-bearing droplet size to intercept, and much higher percentage of particles in larger ranges. Additionally, a study published last week by the Wake Forest Baptist Medical Center found that masks constructed of “two layers of high-quality, heavyweight quilter’s cotton with a thread count of 180 or more, and those with especially tight weave and thicker thread such as batiks” were able to filter up to 79% of 0.3 micron particles (compared to surgical masks, which only filter up to 65% of them). It also found that “A double-layer mask with a simple cotton outer layer and an inner layer of flannel also performed well.” This means that while it is not necessarily as good as a commercial mask, a homemade mask can offer significant protection. Weighing this with the previously referenced research showing that wearing masks significantly reduces the wearer’s ability to transmit virus, it is clear that every one of us should always be wearing the best available masks in public if we want to fight the spread of CoVid-19. My mask protects me and you!

Importantly, there is more to material selection than just filtration efficiency. The best filtering materials might make inferior masks because they are harder to breathe through, causing air to be sucked through the edges of a mask unfiltered rather than through the material, so this gets complicated. This article, based on a number of referenced studies, details relative performance and effectiveness at small particle filtration for a number of commonly available materials. That said, remember that the resistance to air-flow is proportional to the surface area you are trying to breathe through, so increasing area can allow otherwise unsuitable choices to become more feasible.

Likewise, your mask becomes significantly more effective if you wear a faceshield with it. Faceshields won’t stop the really tiny particles from working their way around to your face, but they prevent most of the larger ones, especially those projected by coughing, sneezing, and other “splashy” events, from making contact. They also protect your eyes from those contacts, which is important because your eyes have mucus membranes just like your nose and throat, and so can be an avenue for infection. Note that solid safety glasses can be effective in protecting your eyes, but do not keep droplets from soaking into your mask, so are not as effective!

But here’s the thing. None of these things protect you at all if you don’t wear them correctly and follow proper procedures when wearing them!


  • In general, a mask needs to be sealed to your face well enough that when you inhale, no air is drawn around any edges of the mask.
  • In particular, the curves between your nose and eyes tend to leave a gap between mask material and skin, breaking the seal of your mask. This can be overcome either by wearing a mask that covers the entire nose right up to the eyes so the mask material has a much flatter line to conform to (less effective), or by using a mask that has a bendable metal strip or wire where it passes over the nose that can be formed by the user to fit their particular face (more effective).
  • Faceshields must curve around the face far enough that there is no straight-line path from the air around you to either your eyes, nose or mouth to be effective. If a faceshield is attached directly to a headband, make sure that the headband seals to your forehead. If not, the shield must curve up over your forehead. Likewise, the shield must extend around your face out past the temples.
  • Like faceshields, safety glasses can only effectively protect your eyes if there are no straight-line paths between the air around you and your eyes. Make sure they fully contact your forehead, wrap around the sides of your head back to the temples, and don’t gap over your cheekbones.


No matter how nominally effective a particular piece of protective gear is, if you fail to follow sterile procedures with it during and after use, IT WILL NOT PROTECT YOU AT ALL!

  • Before going out in public with any protective gear, triple check its comfort and fitting (per above). You may be in it for hours, so a) if it’s uncomfortable, you may subconsciously do something that renders it ineffective and b) it is a waste of time and effort to even wear it if it isn’t fitted properly.
  • Always assume any piece of protective gear is contaminated from the moment you put it on, and treat it accordingly.
  • Any piece of protective gear must be sterilized immediately upon removal, and cannot be used again without it.
  • Any facemask worn has to be worn continuously until you are ready to discard/launder it. You can’t pull them down for a moment to take a drink, smoke a cigarette, or “take a break”. (It is theoretically possible to do this if you follow extreme sterile procedures, but I wouldn’t try it if you aren’t an experienced medical professional!)
  • If you wear an N95 or surgical mask, and do not have access to specialized disinfection equipment (you can’t just wash them in soap or alcohol), throw them out immediately after use.
  • If you wear a cloth mask, it must be laundered between every use. You can’t wear it, then stick it in your pocket and wear it again later. That contaminates your hands, your pocket and its contents, and the sterile side of the mask you are about to put back on, at the very least. You’ve rendered it useless.
  • Do not adjust your facemask during use. Its seal against your face is the only thing protecting you, and if you break that seal at all, you have utterly eliminated any benefits it may have provided. Get any comfort or fit issues taken care of before you start!
  • Do not adjust or otherwise touch a piece of protective equipment once it is on unless you can immediately sterilize your hands, because you will transfer anything contaminating it to anything you subsequently touch.

Wear it anyway

Even assuming you completely fail at ALL of the above rules, YOU SHOULD STILL WEAR YOUR MASK. No matter how contaminated/infected you are, wearing a mask, even incorrectly, significantly reduces the likelihood that you will transmit infection to others. You are still helping the general public, even if you don’t care about your own exposure.

So yes, if you wear a mask, there are people who will mock you. If you wear a mask, there are people who will try to shame you because of the misinformation propagated by the government. If you wear a mask, it’s inconvenient, uncomfortable, and a lot of work to get the procedures right. Nevertheless, if you wear a mask, you are helping yourself and others, and if everyone wears a mask, this crisis will be over much sooner, with much less loss of life.


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