Mask Design and Performance Testing

Product Development Insights

December 21, 2022

My background is in product design and development, and this piece has needed to be written for some time.  From 2020 until now the argument has persisted about mask effectiveness --  but missing has been a clear discussion about how masks are made, and how they are rated.  Deciding whether they ‘work’ hinges on knowing some actual details about them.  While I am not a PPE (personal protective equipment) expert, my office in China did look at how to design and produce masks during 2017, as a business case study. 

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The Standards and Materials

What is N95 and who sets the standard?

The industry calls these masks FFR’s (Filtering Facepiece Respirators).  NIOSH, or National Institute of Occupational Safety and Health, is the agency in the US responsible for the standard-setting on various types of Occupational safety equipment.  Think of them as the research arm of OSHA.  Title 42, Part 84 is the Code of Federal Regulations document covering FFR’s, and were written with coal mining and construction hazards in mind originally, which is probably why the standard focuses so heavily on particulates. 

N95 is a dust mask.  It is the familiar type used all during Covid and which can normally be obtained from Home Depot.  FFR’s are rated in three types, series N, R, and P:  Not Resistant to Oil; Resistant to Oil; Oil Proof.  View this as a hierarchy, since R and P-rated masks must withstand oil environments, which would otherwise degrade the performance of N-rated filter materials.  You may come across R95 or P95 masks, usually at a higher price but equally as effective.

“95” refers to 95% penetration, or capture of the standardized test particles in the test apparatus.  For “N” masks, the test particles are an aerosolized NaCl solution.  The test apparatus is essentially a pressure box, with the mask sealed so that the solution is forced into or through it at various pressures, to simulate increasing levels of use (i.e. heavy breathing).

In our case study, 95% was too low.  The imagined scenario was an urban warzone, with unknown contaminants or biologicals.  As an emergency product, it needed to be small and re-useable, and not require power filtration.  Fortunately, NIOSH specifies higher-level N99 and N100 standards, along with their “R” and “P” counterparts.  As the numbers imply, these capture test particles at no less than 99% and 99.97%, respectively.  Did you ever hear those discussed during Covid?  Me neither, but N99’s are what we procured for ourselves in 2020.   

What about that particle size?

Readers may be aware of masking debates related to particle size.  The NaCl aerosol specified by NIOSH has 0.075 μm particles (that is micrometer, a.k.a. micron), with a +/- 0.02 tolerance.  Less than a tenth of a thousandth of a millimeter.  NIOSH materials also reference a metric called MMAD (mass median aerodynamic diameter), with a value of 0.3 μm.  So MMAD is triple…which one to use?  Mass turns out to be very important for these tiny particles, in how far and fast they travel -- like down into the brachia of your lungs.  Without a scientific deep dive, know that both numbers are in the same general range of SARS-COV size. 

Going with 0.1 μm for the sake of argument, NIOSH considers this the Most Penetrating Particle Size (MPPS) relevant for testing.  As explained in their science blog, the MPPS means nominal worst case.   It turns out the filter material will stop both larger and smaller particles at an even higher percentage rate.  How can this be?  Because smaller particles are contained by electrostatic forces, and even Van Der Waal’s forces (molecular).  MPPS is chosen as the most difficult sized particle to trap, by a combination of its size, shape, and mass.  Larger particles of course encounter physical obstruction or entanglement.  So it does not necessarily follow that small particles slipping between fibers have a clear shot.  At least 95% of them will still be contained by these other forces, and they are not easily dislodged.  The common misunderstanding of a 0.1 μm particle falling through a 0.3 μm mesh is too simplistic.

Notably, there has been an active debate since at least 2009 regarding NIOSH’s lack of procedures or ratings to test filter respirators with Biological Aerosols.  The official position is that a particle is a particle.  The medical community is not so sure.  At least during 2014 when this was written, there was healthy discussion on the matter.  Until actual testing is written and performed on biologicals, I consider NIOSH’s mask ratings to be theoretical for viruses and bacteria.  It is just personal gut check; I want to see the evidence rather than assume.

Non-Woven Textiles, and Mask Construction:

NIOSH does not specify mask details beyond performance-related requirements, which leaves room for experimentation by manufacturers (a good thing).  Sewn, heat seamed, and compression molded are the three primary styles.  Minimum specs are:

a)     For re-useable masks, the presence of an outer layer is required, and must seal properly.

b)     Passing the standard tests described above, and being prominently labeled.

c)     Having a “head harness” that provides adequate tension and even pressure distribution to the face.  It looks to me like NIOSH advises against ear-loop bands for this reason.

d)     Being non-irritating, which often means masks will have an inner layer for comfort. 

Non-Woven Textiles are the filter material of choice by manufacturers, as they are able to be controlled or ‘tuned’ to various filament sizes and densities.  They have a preferred cost / benefit ratio, in business speak.  There is a wide variation available, but they are predominantly mats of synthetic polymer filament, and are not biodegradable.  Some masks are available with materials like silk or sheep’s wool, which have a lot of promise in my opinion.  For the purpose of this discussion though, assume the sky is the limit on choosing the right Non-Woven material for a given performance goal.  As long as the raw materials and assembly process remain consistent, there is no reason to think that a NIOSH-rated mask is anything less than the rating claimed.  As long as.

What about fitment?  Is it really so critical?

Yes!  What makes this a hot debate, and a logical fallacy, is that the predominant surgical-style masks worn all throughout Covid by font-line personnel, do not fit and are not N95 rated.  They feature ear-loops, no shape for sealing the face, and have a terrible efficiency variance from 17% to 90% .  NIOSH doesn’t even rate them, as they are FDA-approved gear.  For a supposedly deadly pandemic, this kind of mask should have been the last resort, especially with all of the lecturing the public endured about making sure your nose was covered, and warnings not to-re-use a disposable mask.  Remember this the next time someone extolls a “triple layer surgical mask.”  There are such things as N95s surgical respirators now, recently approved by NIOSH, but you rarely see them.

Fitment is crucial when 20% of breathing air may escape or intrude around the open edges.  Especially for our hero front-liners.  So it staggers belief that our pandemic overlords are OK with surgical loop masks, cotton ‘fashion masks’, and dirty half-worn N95s.  It shows they are really not serious about virus protection; their motivation is something else, and they are just making rules to follow.  That is partly what drove me to write this article.  Covid may have been flat in terms of its flu-like lethality,  but we should think about the next pandemic, not the last one.  Suffering ill-conceived guidelines was an annoyance; being prepared for a real crisis is another matter. 

What about KN95 (China) masks, and foreign standards?

Chances are most people gave no second thought to the “KN” rated masks, if they even noticed.  After all, it still says 95 so maybe it is the same.  Before March 2020 you would never have encountered one outside of Asia, since it is a Chinese rating.  These were only made available in the U.S. under Emergency Use Authorization (EUA),  the same authorization that gives indemnity to vaccine manufacturers.  There are still plenty of KN masks available online, despite the supply shortage being long past.  How good is the KN standard, and how faithfully is it enforced?  No idea.  EUA authorized these foreign masks during the Great Shortage of 2020.  As with anything Covid, doing one’s own research has become essential, since the medical and scientific communities have let us down repeatedly in recent years.

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Test Labs and Supply Chains

How important are test labs in all of this?

VERY, so here we go.  Every commercially available product must conform to some type of standard, such as we have been discussing with NIOSH.  Readers may be aware of standards such as UL, CE, CSA, ASME, and so on.  You may not know that foreign test labs are common, having approval by these regulatory agencies to conduct standardized testing abroad.  As with anything, your results may vary.  I can say that as someone who has managed teams seeking to pass ratings in both the US and China, and having spent time in some of these labs.  Outside of western countries, human motivation plays a significant role in the results one may get from that test lab.  I have analyzed products that never should have passed their rating test, and yet carry a rating sticker.  Sometimes products fail in one way, only to pass in another, depending on who is running the test. 

The best companies do their own internal testing, or partner with the only best labs.  A 3M mask, with filter material that likely came from DuPont, and tested by NIOSH themselves….that is trustworthy.  But a ‘Great Life Masks’ or whatever -- with Indian filters, Chinese assembly and testing, and sold only online -- is a more risky endeavor.  Many companies jumped on the bandwagon to sell masks during the last three years.  Their packaging will often be emblazoned with patriotic colors and convincing terms, because slick marketing works.  I hope this paints a clear picture for you, Reader.

What does it have to do with supply chains?

Supply chains are the bane of every product developer.  Non-Woven Textiles with their variety of types, densities, layering, etc. are the critical spec component of the system.  They will be procured in large rolls for mass production.  500 meter length, 5.5 ft. width, that would probably be a small roll…imagine the weight.  Let’s say a specific fiber product was chosen by the development team, and qualified under NIOSH testing, and therefore needs to be the same as used in production.  But as soon as there is pressure on the supply chain, this textile is out of stock.  Big problem.

This scenario was common during Covid, across many supply chains.  Countries were commandeering supplies like textile rolls and mask molding machines.  Taiwan’s government assumed oversight of mask production and control.  China appropriated even foreign-owned factories, if they were critical.  Orders of PPE product were being seized at airports by governments who were desperate to procure supplies. 

When we researched the supply for our test case, the three primary sources of Non-Wovens were China, India, and the US.  Without delving into the geopolitics and trade route logistics, we can summarize it: the best mask producers have secured a reliable source of components, either by vertically integrating, or by locating nearby their suppliers, or keeping two years of supplies in stock.  In a crisis then, the unknown companies will often fail to deliver your order, or tend to substitute untested materials.  Prudent consumers will use this down-time between pandemics to secure whatever supplies are needed for next time, thus avoiding sub-standard choices and panic buying.  Maybe the last boxes available at WalMart are not the ones you want.

Then there is the problem of quality:

Someone has to say it: apart from Japan, most Asian sourced components are notoriously out of spec.  Usually under spec.  I cannot stress enough how often this happens.  Order a batch of screws and discover 90% of them are in the 10th percentile for size – not a standard bell curve or tolerance range.  This abnormal distribution is the supplier’s attempt to ‘short’ the material while remaining within spec.  There is something cultural at work here, which requires a lot of effort to overcome.  What you may call cheating, or contract violation; they would call ‘looking for opportunity’, or ‘building trust’.  Take this seasoned observation for what it is.  I am describing a kind of pervasive thinking that is a fact of life here, from Indonesia, to Vietnam, to China, and just about every Asian / ASEAN location I can think of.  I ended up marrying and settling in the Philippines and yes, it is the same too.  I euphemistically call it Being Frugal.

So here is the scenario that might play out for our theoretical N95 Non-Woven filter materials:  By the second year, the filter material would probably be under spec, forcing us to either hope NIOSH doesn’t notice, or requalify the mask rating with another filter.  The fragility of the supply chain was already a big problem, and now this.  Imagine the hair-pulling that developers go through trying to populate components on a circuit board, or to build an iPhone -- making sure the product is identical in Year 2 compared to Year 1.  It is only possible by robust risk management practices, which is a culture only the biggest and best companies seem to have.

This was just a glimpse.  Most mask companies navigating this production web are relying on fragile supply chains, or questionable test labs, and opportunistic suppliers who are probably lax on the product spec.  Then there is the huge annual workforce turnover rate, currency volatility, and ever-changing regulations.  What I am saying, Readers, is that faith in the system is probably misplaced, so let the buyer beware.  If the company making masks is also making socks, then it may be time to worry about quality.

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Putting it Into Perspective

Here are my working recommendations, knowing what I know.  You can add to it your own observations:

1.     We don’t really know how effective the masks are against viruses, because they were not specifically tested for it.

2.     If the threat is truly dire, look for the 99 and 100 rated masks, even though certainty is not possible.

3.     To get the highest trust possible, buy from a reputable company with its supply chain in your own country.  Secure them now, while we are between crisis cycles.  

4.     Consider that replaceable filter inserts may be easier to obtain (or make) during a prolonged crisis, since disposable masks will all be snapped-up by hospitals and governments.  It makes more sense to have a mask that you know fits and seals well, and is re-useable. 

Current research and testing by NIOSH is vectored toward nano scale as the next frontier of filtration, and developing better wearable powered filtration systems (known as PAPR in the industry) at 100% efficiency for medical front-liners.  This tells me they recognize better protection is needed, which again underscores the inadequacy of the Covid standard for masking in public.  What we saw during the recent mass delusion was, basically, anything you put on your face is OK.

Homemade Masks:

I will close with DIY masks, which I have been critical of in the past.  Friends and family in the US were engaged in home mask-making during the height of the 2020 panic, while I was scrambling in the Philippines to get supplies of N99 filters.  Many here were happy to just put a bandana over their faces.  Cotton can be from 5%  to 80% efficient.  Which one was your church group using for its homemade masks?  What about those Lycra masks from your workplace, with the company logo?  The spirit of DIY is fantastic, it is just the execution that may have been a little un-serious.  Something is better than nothing seems to have been the operative theory of most people.  Maybe I am the one looking at this in the wrong way.

Yet almost three years later, many of the Something-Is-Better-Than-Nothing crowd are still at it.  For them, the air itself is suspicious, and so is that visitor ringing the doorbell.  At a local mall a few weeks ago, 70% of shoppers were masked despite no requirement to do so…and most of those were useless cloth fashion masks.  Fear has profoundly affected the collective psyche, even though the death rate was never worse than Influenza.  Maybe this was the whole point of the Covid exercise.  Our N99s are still in the package, unused.  We bought them as a cautionary measure when not much was known.  By April 2020 it was apparent that Covid itself was not risky enough to justify wasting them.  Our house all caught Covid eventually, recovered normally, and never had it again.  We never wore masks, and did not take the vaccination.

Maybe either point of view could be considered paranoia; maximum protection, or any random piece of cloth.  It is not easy discerning what is real in the fog of this info war.  What is clear to me: they want you to put something on your face, even if it only marginally works.  That is a major alarm bell.  I want the damn thing to work if there is really a need for it.  And if there is no real need for it, then get out of my face with your guidelines.  It brings to mind a scene in the movie K-19 in which a Soviet crew must enter the reactor room to repair a coolant pipe, wearing nothing but a chemical suit.  There were no radiation suits available, you see.  So the doctor would take dosimeter readings and say, “yep, good,” but the men still died from radiation exposure.

If the worst case happens:

My outlook on DIY masks has changed over time.  Because for a true dystopian world-crisis, they may be the only long-term solution.  Don’t expect mask supplies to last any longer than six months, except for those being hoarded in government warehouses.  We should applaud those who are actively working on this problem now, by doing their own testing on things like Hepa filters and vacuum cleaner bags.  Home grown solutions would likely be all we can rely on in such a scenario, just like water from your own well and veggies from a local garden.  So if it turns out that 3 layers of silk pajamas do a 99% job of filtering a contagion, then this is important to know.  Until the grassroots figures it out, I urge you to have enough N99 or N100 stock on hand along with your other preparations.  The supply chain is not dependable in its current state, and is getting worse instead of better.

So take this guidance or don’t, Reader, my goal was to present you with the information.  The next pandemic has already been gamed-out by the usual suspects, judging by their latest exercise in October called Catastrophic Contagion.  In its description, they imagine a higher fatality rate than COVID-19, disproportionately affecting children and young people.  Let’s see if Mr. Gates’ and the WHO’s amazing powers of prediction come true again; and if it will be real, or an overblown figment of the collective imagination.  Maybe your fear trigger is those evil Chinese or Russians, rather than Fort Deitrick or DARPA.  I don’t know what will happen, but the final act is shaping up to be a whopper -- or a WOPR depending on your perspective (10 points if you get the pun).

As I often point out, we live in a world out of control.  By the Biblical clock, it looks like a rapture event could be soon.  The dire predictions of global depopulation sure make sense to me, based on recent history.  But we never truly know, do we?  I will not live in a state of fear, and I encourage you to live boldly as well.  Knowing that you know, if you belong to Christ, and being vigilant.  The enemy doesn’t stand a chance.    

Visayas, out.

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https://www.cdc.gov/niosh/ppe/

https://www.cdc.gov/niosh/docs/2021-107/pdfs/2021-107.pdf?id=10.26616/NIOSHPUB2021107

https://www.ecfr.gov/current/title-42/chapter-I/subchapter-G/part-84

https://www.federalregister.gov/documents/2020/04/14/2020-07804/approval-tests-and-standards-for-air-purifying-particulate-respirators

https://blogs.cdc.gov/niosh-science-blog/2014/04/02/respirator-filter-testing/

https://blogs.cdc.gov/niosh-science-blog/2009/10/14/n95/

https://www.cdc.gov/niosh/npptl/stps/pdfs/TEB-APR-STP-0059-508.pdf

https://blogs.cdc.gov/niosh-science-blog/2020/04/23/imported-respirators/

https://www.cdc.gov/coronavirus/2019-ncov/hcp/ppe-strategy/international-respirator-purchase.html

https://www.centerforhealthsecurity.org/our-work/exercises/2022-catastrophic-contagion/