Healthcare PPE: Full Face Snorkel / Scuba Masks with Existing HME Connected with 3D Printing

For medical / healthcare professionals in need of protective gear, or perhaps without PAPR gear. Several groups have shown this approach to be valid to protecting the wearer from the disease. The images below link to a Pall element, and a past paper on their use in infection control.

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FAQ on Medical PPE, Facemasks, N95, etc.

These are my personal views and not that of any employer. The best resource on this is the summary from the Smart Air Filters website by their CEO, Paddy Robertson.  If you want to approach problem solving in manufacturing – start with Goldratt.


Do you know that healthcare providers and hospitals need masks?

Yes, we do! Every part of the global mask supply chain has been running flat out since late 2019, when the seriousness of the Corona virus outbreak became clear. Materials are moving through the supply chain as fast as they can.

I’d like to buy what the mask makers buy, when can I get some?

Right now, every plant I know that is part of this supply chain is running flat out. Rolled good plants can’t keep up with orders. Facemask plants can’t keep up with orders. This is an efficient supply chain with experienced, professional manufacturers that know how to get the most out of their people and plants. With the current public health emergency, most companies are not taking on new orders. The fastest way to get materials out is to follow the current path.

If a roll was sold to you, it would be like taking a mask away from a physician that really needed it.

I’m with a hospital that really needs some, can you ship me something?

Hospitals should be reaching out to distributors or to mask makers. A hospital spending its time looking for rolled good inventory is wasting its time. Focus on getting the next nearest shipment of masks.

Mask Specific Questions

I’m going to use HEPA filters since that is the highest standard – won’t that work?

HEPA is both a standard for completed filter elements used in wafer fabs, flat panel TV production, and drug making, as well as a commercial claim. For the HEPA standard, most filters are made of wetlaid glass fibers or they use PTFE – material similar to that used in Gore-tex jackets. Both of these materials have very low air permeability – healthcare workers could not breathe through them! While they would be very efficient, physicians would have to move the mask to breathe, making the whole exercise pointless.

There are commercial HEPA-claim filters (not ‘True HEPA”) that use charge to get higher efficiencies. For more on charge, see below.

I need polypropylene HEPA fibers, do you have them?

Fibers can’t have a HEPA claim – it is only used on the finished HEPA element. As discussed above, polypropylene (“PP”) is not used in HEPA.

I may have the material wrong, we are looking for the HEPA filter material that does uses a polymer instead of fiberglass?

Your options would then be to use a PTFE – which would also not be breathable. There are very small volumes of materials with synthetic HEPA on the market. They would be difficult to use in a facemask.

We’ve seen rolls marketed online, but we haven’t been able to secure any in a timely manner?

Almost every government globally is struggling to get appropriate PPE for their healthcare workers. I would not believe that a container will leave from a foreign site and get to your location. If you did receive a roll, I would expect it to be a grade that is not commercially relevant to your work.

What can we do then?

I’d follow the guidance here and make:

  • a form fitting mask
  • using two layers
  • that somehow incorporates charge –
    • Use a pocket to include a swiffer refill
    • make one of the layers wool, or some other ‘static-y’ material

American Based Manufacturing Questions

Why did all of the manufacturing go to China?

My personal impression is that the capitalist pressure to ‘maximize’ shareholder return did not line up with a common-sense appreciation that in times of needs, a culture needs to be self-reliant. Beth Macy’s excellent book Factory Man, shows how the US effectively traded the jobs of millions of Americans in exchange to help bring China out of poverty, but this trend continued to the point of absurdity.

Doesn’t that make you angry?

There are news stories about angry participants in this supply chain, but my view is that it makes me feel more sad than upset. Even now the cries of, “we don’t know how to do this in America” – c’mon. Yes, we do. It is just a skill that has been ignored.

What other products are made with these materials?

Nonwovens are used in many industries. They are used in wound care, in car production, as surfacing veils for aerospace, and as crucial components in filter elements for the production of pharmaceuticals and drinking water.

Does everyone know hospitals need masks?

Yes!  Everyone who works in the medical PPE supply chain is working overtime and doing everything they can to push masks out to the hospitals.  There is a lot of PPE still made in the US, and that includes not only facemasks, but also gowns, medical barriers, the filters used in the ICU, and the filters in cartridges.  

How does the mask supply chain work? 

There are two main parts to the supply chain:

Rolled Goods.  Rolled good makers buy polymer – mostly polypropylene – and use it to make a nonwoven.  Several layers of nonwovens are then brought together by the next step in the supply chain, to make the mask.  The efficiency layer in a facemask is most often a charged meltblown.  

Converters.  Facemask makers receive rolled goods (sometimes in rolls that are 2 meters wide and kilometers long), and then convert them into facemasks.  Surgical masks are sewn.  N95 (NIOSH masks), and their cousins R95 and P95 (where R indicates some oil Resistance and P indicates even more) are thermo-formed and are more form fitting.  

What do you think about the recent 3M news increasing output to 100 million per month?

That’s great news.  I’d interpret that to mean that a converter, with some vertical integration – 3M and others make some Rolled Goods, but not all – is now capable of shipping 100 million masks per month.  Mask makers are often the constraint in the supply chain. The automated production lines that make masks are mechanically complex and can take a long time to build. Nonwovens lines tend to be larger and are used for many different end markets. For Nonwovens lines, it tends to be more an issue of pivoting the line to make this specific kind of material, and ensuring you can hit the standards of the grade that is required.

Why is getting masks to hospitals so hard?

The supply chain started running very aggressively as demand ramped in Asia in Q4.  China is a face mask exporter, and as China shut down its production, there was a double hit to production.  US demand was called up to not only service US demand, but to also export (before Corona crossed to the US).  Chinese supply has only come back slowly, many plants there are still closed – it is not clear if they have capacity to export now.

If anything the supply shock of China shutting down prepared the US supply chain to be ready, now all that capacity is being redirected here.

What guidance would you share to help medical professionals in the event of shortage?

Cough droplets from patients with corona virus are a safety issue.  The atmosphere is contaminated with an unsafe particulate; cough droplets full of corona virus generated by sick patients.

  • Declare war on the droplets.  Droplets are 100 micron – 5 micron in size. Follow common indoor-air quality and safety protocols.
  • Use room air cleaners.  
  • Use whatever PPE you can.   (DysonCamfilAustin Air, etc.)
  • Never use a wet facemask – wet helps the virus travel through the mask.
  • Look for ways to get charge into the mask.

How do charged masks work? 

Charge in the fibers – static electricity – attracts the particles as they flow through the mask.  This improves the masks efficiency.  Without the charge, most masks have very low efficiency.  For very small particles – 0.3 micron and smaller, polypropylene meltblown masks only work because of the charge.  

Does the charge attract viruses to my mouth?  

No – but that’s a good question.  The charge is very weak.  Think of the dangerous particle drifting in an ICU Room – it has many forces exerted upon it.  When a mask wearer inhales, that force draws the particle towards the wearer’s lungs – rather than pass through the mask, the charge acts as a special force that pulls the dangerous droplet to contact the mask.

What materials have charge that I could use?

Swiffer replacement refills have charge.  Wool has charge.  Anything that has static electricity naturally could be useful to use.  

What steps would you suggest so this does not happen again?

MAP THE SUPPLY CHAIN. I’d make a very clear map of the supply chain. 

  • Know every hospital
  • Know every distributor that sells to those hospitals
  • Know every mask maker that uses those distributors
  • Know every rolled good / nonwoven maker that sells to those mask makers

1. Canada had an inventory of N95 masks that had dry rotted.  Pay for a study of how to extend mask shelf lives.

2. Store inventory.  Make up fresh rolled good inventory every X years, such that it can be quickly converted to masks.

PRE-PURCHASE CAPACITY AND CAPABILITY. Pay for facemask capacity. Production equipment for masks is notorious for losing money.  Have the gov’t or other group buy equipment and pay some modest fee to have it maintained and ready for use.  

BAD IDEAS. Don’t invest in a horde of inventory.  Invest in systems and processes that can handle a future threat of unknown size and scope.  For instance, NC State was going to get a Nat’l Academy center of excellence on advanced PPE, that was never funded even though it was approved.  That would have had small volume production, but most importantly, it would have produced 100s of grad students with work experience in these fields.  As a culture we have not produced many people who can answer these questions.  

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Medical PPE and Corona Virus: The Ideal and Improvisation

I am not an expert in this space, but my credentials are reasonable. This is my personal outlook, not that of any employer.

There are heartbreaking stories of hospitals calling for PPE – especially facemasks – and courageous stories of people cobbling together devices to reduce the likelihood that a healthcare provider could get ill while treating a patient with COVID19. This post leans heavily on information from the Smart Air Filters website written by their CEO, Paddy Robertson. I summarize those documents here.

Step 1: Reduce the Danger of the Environment; Declare War on the Droplet

The virus dies as an aerosol. It lives in droplets. When there are enough coughing patients in the room, the likelihood of infection grows because the air is full of droplets.

Before being concerned with PPE, address this issue as much as possible:

  • Increase air turn over.
  • Filter the air.
  • Change the filters often.
  • Put out specific air treatment technologies – such as room-air cleaners, ionizers and UV-C light, that are known to kill the virus.
  • Add room air cleaners (DysonCamfilAustin Air, etc.)

Before Improvisation – How do Masks Work?

Masks involve several layers of technical fabrics (often nonwovens or other porous materials). The performance of the mask comes from the combined performance of the materials.

Types of Masks

N95 or NIOSH masks (also N99, N100) are designed to capture particulate. They fit snug to the face, but they are not necessarily droplet proof.

Surgical masks are droplet proof, but they are exposed on the sides, so that an aerosol could get around them.

Surgical N95 Masks, or S95, have the best of both worlds. They have high capacity of an N95, but have also been through the droplet testing of the surgical standards. (Nelson Labs is the dominant provider of testing to these standards, including ASTM-F2100.)

The Ideal Mask & PPE For Corona Virus

Given the dangers of COVID19, the ideal mask would appear to be an S95 mask, that is changed out on a regular basis. All of these masks are designed to be disposable. It would be reasonable to wear more extreme protective gear – protective shielding – and perhaps even have a powered air purifier attachment.


Masks work because they have the right amount of breathability (air flow), efficiency (what % of particles do they catch), and life. Life is the easiest – masks are designed to be disposable with short lives.

Efficiency is harder. Small particles – those below 0.3 micron – the formal cut off of HEPA measurement, are often captured with charge. In filtration particles can get caught primarily by making physically small holes (mechanical filtration, where there is a physical mechanism that stops the particle), and electrostatic filtration (where the filter media – the facemask) has a charge, that is used to attract the particle. For small particles, especially below 0.3 micron, that electrostatic force is powerful enough to have a big impact on filtration. Charged filter media is widely used in facemasks.

Filtration has a lot of bad jokes – this one is about breath-ability and air permeability. A table is 100% efficient at filtering your dinner from hitting the floor. Get it? However, the breath-ability is awful. Likewise, if you make a facemask that is too efficient, it is hard for the wearer to breath. When the air flow gets too low, or when the resistance is too high, this hurts the wearer’s compliance. Healthcare workers start to slide the mask over, which defeats the whole point of the mask in the first place.

The layers of a surgical and also S95 masks, are also going to have a hydrophobic treatment to prevent droplets from passing through, and therefore be able to slow down the passage of bacteria and viruses. They do not stop the water flow forever. If we run a water hose over a surgical mask, the mask becomes inundated, and its useful life is over.

Thoughts on Mask Cleaning

There are two characteristics of the mask that are important to preserve in cleaning:

  1. DRY. If the mask is wet, it is likely easier for bacteria and viruses to get through the existing fluid. Make sure the mask is dry!
  2. CHARGE. Charge is part of the efficiency. This improves also by drying the mask out, but also look to give it some static charge. Rub it on wool, run it over an incandescent lightbulb, etc.

My personal priority would be to focus on not getting the mask too wet. I’d rather have multiple masks that I’m swapping out often, making sure that no liquid ever gets through, than to have one ‘new’ mask that I wear all day.

Article 3: Is Washing Masks Effective After Virus Exposure?

Is Washing Masks Effective After Virus Exposure_ – Smart Air FiltersDownload

Masks work worse after washing. Don’t wear a wet mask! Masks depend on charge to work. Find ways to add back charge.

List of Improvisation

If I had to, I’d:

  • Use a form fitting mask design.
  • Use two pillow cases from the research above.
  • I’d add in a pocket to put in a high air perm insert, and would use something like a swiffer dryer sheet. Modern masks work based on charge.
  • I’d never wear a wet mask. A saturated mask gives disease a faster path to travel.
  • I’d do everything possible to reduce the droplet danger in the room.
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DIY Face Masks, Homemade Masks, Facemask Cleaning, and N95 vs Surgical for Corona Virus; The Excellent Paddy Robertson Posts from Smart Air Filters

I am not the author of these posts – they are from the Smart Air Filters website by their CEO, Paddy Robertson. With the COVID-19 and Corona Virus emergency, many are struggling to download these articles to make use of their information. I’m only providing them here until his website is back up or the current quarantines in the US and Europe are over. (Thank you, Mr. Robertson.)

These articles cite a primary source as their inspiration: (2013) “Testing the Efficacy of Homemade Masks: Would They Protect in an Influenza Pandemic?”

Article 1: What are the Best Materials for DIY Masks?

Use two pillow cases, that works well enough. From a personal standpoint, I’d add a swiffer dry sheet to get some electrical charge.

Article 2: Can DIY Masks Protect from Corona Virus?

They are about 50% as efficient as a surgical or N95 mask.

Article 3: Is Washing Masks Effective After Virus Exposure?

Masks work worse after washing. Don’t wear a wet mask! Masks depend on charge to work. Find ways to add back charge.

Article 4: N95 vs Surgical Masks – Which is Best for Corona Virus?

It depends. In a room with lots of droplets, N95 has a better seal. Surgical protects against droplets.

Article 5: How Long do Pollution Masks Last?

Get 3 hours out of your mask!

Best Illustrations

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ICU, IAQ and COVID-19: Hospital and Intensive Care Unit (ICU) Indoor Air Quality (IAQ) and Corona Virus

[I’m not an expert, but based on the degree of panic and activity and Corona Virus, I’m writing this in an attempt to be helpful.]


  • The virus does not survive as an aerosol like measles, but it does appear to survive longer as a droplet than rhinovirus. I believe the reports of Dr. Ian Mackay (Flight of the Virus), that the virus does not survive outside of a droplet.
  • Physicians who have treated this disease have died from exposure to the virus. (Dr. Marcello Natali in Italy, and Dr. Li Wenliang in China.)
  • PPE shortages – facemasks, etc. – are putting physicians at risk.
  • However, before addressing the PPE shortage, how can we reduce the risk of the ICU?

Airborne Droplet Dangers of the ICU with Corona Virus

Patients are coughing.

The patient is putting droplets – laden with corona virus – into the air.

If inhaled in sufficient volume, that virus is a danger to infect anyone in the environment.

All of the previous dangers of the ICU still exist – the extreme nature of this airborne droplet danger changes how safety should be approached.

Safety Approaches to Air Quality Danger

If a production site works with particulates that can explode, there are clear OSHA guidelines for how to work with that material. In a similar fashion, from working with industrial mix stations – if there is explosion risks, there are basic guidelines from Europe as well in how to manage that risk. For certain flammables under low concentration, the air in a room must turn over 6 times per hour. As those concentrations increase, the air turnover per hour increases – as high as 10 or more times per hour.

If there are enough cough droplets in the air from corona, there is risk for anyone in the room. To reduce that risk, follow established standards:

  • Turn the air over. Keep the air moving.
  • Reduce the life of droplets by reducing the humidity.
  • Filter the air to capture droplets on filter media.
  • Change out air filters as often as possible.
  • Put out specific air treatment technologies – such as room-air cleaners, ionizers and UV-C light, that are known to kill the virus.

If I was running an ICU and was Concerned About Corona Virus Exposure

I would do everything possible to reduce the indoor air quality risk, which would include:

  • Making sure there was lots of air turnover.
  • Make sure that air turnover is filtered.[1]
  • I would change the filters often for the ICU area. Daily would not be too much.
  • I would add room air cleaners (Dyson, Camfil, Austin Air, etc.)
  • I would add UV-C lights (and appropriate eye protection when using them)
  • I’d do everything I can to make a hostile environment for droplets.
  • I’d open windows and try to let in as much sunshine as possible (UV, new make-up air that is uninfected, air flow, and improved evaporation).

1: Question – Do Cruder, Non-HEPA Filters Work?

Yes, they are better than nothing. Fibers in filters have capacity. They catch dirt. Many types of filters only work when they are loaded with dirt – this dust-cake is what creates the actual filter layer.

The virus is also traveling in droplets which can be as large as 100 micron. A MERV 5 filter is 20% efficient, and at MERV 7 is 80% efficient, and it only gets better as it gets higher. If the air is being turned over multiple times per hour, then the there is a high probability that droplet – and the related virus get trapped.

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Personal Credentials on Porous Materials, Facemasks, Indoor Air Quality, Hospital ICUs, and Infectious Disease

I’ve spent nearly 15 years working with porous materials – helping companies develop improved porous material products, designing the production systems that deliver membranes and nonwovens, and overseeing these supply chains. I am not a facemask expert – but I’ve worked all around this space and led several facemask product development efforts. I am not an infectious disease expert. I am not an expert in the design of hospital ICUs.

I’ve served on the board of INDA, the US nonwovens trade association. Nonwovens are the primary materials used in facemask production. They are also the dominant material used in filters for indoor air quality (“IAQ”) worldwide. Through that, I’ve joined multiple ASHRAE committee meetings and been a featured speaker at filtration, fiber, aerosol particulates, and membrane trade shows.

The nonwovens and engineered materials industry plays a major role in producing materials essential to reduce the spread of COVID-19.  From disinfecting wipes to face mask material to Personal Protective Apparel and more, INDA member companies are providing products to help people be safer in difficult environments.

From the INDA website on Corona Virus

There are many standards relevant to how IAQ is measured, how filters work, and how to measure the capture of particulates – especially when those particles (or aerosols) may involve bacteria or viruses. Most of my time now is spent with the standards around liquid filtration – B. diminuta and S. marescens.

These are my personal opinions – not those of my employer. I currently work at H&V, where I am responsible for the liquid filtration portfolio at one of the world’s largest makers of porous materials, I was CEO of Elmarco, the leading global technology provider for nanofibers and electrospinning – in total I spent nearly 9 years pioneering the most advanced fibrous products globally.

My undergraduate degree is in biology. Prior to my time in porous materials, I’d worked in finance with private equity groups that invested in the healthcare, life science, drug development, biopharma and other supply chains.

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Constraints, Corona & Covid: Update with Everlywell testing, Chloroquine and Plasma Treatments

Goldratt teaches that to improve a system, we must identify the constraints, and then systematically work to relieve them. There are several constrains in the global pandemic:

  1. Is the information about the Coronavirus accurate?
    • How does it spread? (It does *not* aerosolize.)
    • When do symptoms become evident?
    • How many people who get the disease require medical assistance?
    • How many die?
  2. Can we test and identify people that have the virus?
    • Everlywell, an Austin, TX start up that was on Sharktank, has announced a future personal test kit.
  3. If someone comes down with COVID19, is the right equipment available?
    • PPE for the physicians (facemasks, etc.)
    • Respirators and ventilators for treatment
  4. Are there medicines and therapies that can treat or prevent the spread of the infection?
    • Is there a vaccine?
    • Are there medicines which help those who are infected?

A third medicine has been identified – another anti-malarial drug, Chloroquine. It is sold by Aventis (formerly Rhone Poulenc) under the trade name Nivaquine. A less aggressive version, hydroxychloroquine is also shown to work.

It also appears as if blood transfusions from those who have had the disease may also help immunize and activate the immune systems of others.

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Constraints, Corona, and Covid: Treatments – Remdesivir and Camostat Show Promise

Goldratt teaches that systems should be judged by their output, addressed at the highest level, and constraints should be removed. For a patient that has the disease, some treatment options are emerging.

Remdesivir: Nucleotide analog

Produced by Gilead, this class of drug has existed for some time and has been shown to perform well against RNA virsues.

Camostat: Serine protease inhibitor

A German research team found that a cell line was susceptible to Sars-2, and then showed that Camostat was capable of slowing and perhaps stopping the damage created by the virus.

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Corona Virus, Public Health, Goldratt, Goals and Global Health

As SARS-2 containment and COVID19 treatment increase in importance – many global, regional and national systems are activating, cooperating and working towards solutions. The complexity begs for an application of Goldratt’s principles:

  1. Pick a Goal.
  2. Identify constraints between the current setting and your goal.
  3. Remove the biggest known constraints.
  4. Achieve Goal.

The Life Science’s tradition of “First, do no harm” is a noble and well established goal. Do not diminish the public’s health. The virus does diminish health, so stopping its spread (while doing “no harm”), becomes important, as does treating those who have contracted COVID19.

Developing Data

In The Goal, Alex notably never has to deal with an absence of data or a resistance to data development and usage. Alex also exists in a world where there is a strong sense of community and teamwork.

Neither exist clearly in the global response to the new Coronavirus. In the US now, testing capacity is limited. Globally, nations are releasing ‘test’ data that has come under question and faces skepticism.

Testing for Corona

If testing and data are crucial to developing a response to the disease, then that is the current constraint. Goldratt teaches to remove the constraint; testing must be addressed.

Testing is currently performed with the polymerase chain reaction (“PCR”) a method widely taught in high school and college biology classes that breaks, copies and then measures DNA for comparison. Specifically, a reverse transcriptase PCR is used, and there has even been success in using a chest CT scan as a diagnostic tool.


Testing for Corona is the first step in creating an appropriate response. There is a lack of testing equipment;

  1. Create more testing equipment – reduce the constraint directly.
  2. Identify bypasses to the constraint – such as using Chest CT scans, as has been shown to be predictive of positive diagnosis of Corona.

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Fluid Notes: Solar Power, Ceramic Pressure Exchangers and the Cost of Desalination

A group out of MIT made an announcement that they are able to harness solar power with a low cost – lower cost than a conventional desal plant – that was able to deliver 6 liters per hour per square meter of collector. Published in the Journal of Energy and Environmental Science, the paper outlines a device that functions as a multi-layer still, using several evaporation and condensation steps to produce water that exceeds current drinking water standards.

As users on a Hacker News thread pointed out – this is a very energy intense process that requires 173 kWh of solar energy, compared to the 3.2 kWh often used for all of the processes in a conventional desal plant like San Diego’s Carlsbad site. The MIT group isn’t radically altering how the current municipal distribution network for drinking water would work – it is instead providing a technology that would allow for a more off-the-grid (“OTG”) approach for desalination, in the same way that generators allow electricity in wilderness cabins. Depending on the setup costs, it’s easy to see a set up where intercoastal waterways and other marshy areas could support units like this that generate reliable small volumes of liquid to support a single household that might not otherwise be able to justify the cost of a desal situation.

Desalination Materials: Ceramic Pressure Exchangers

Looking at how an OTG situation could change how certain areas can create clean water at a lower cost calls back to past technologies that allowed the centralized growth of desalination. Desal occurs at high pressures – this is one of the biggest differences between air and water filtration.

Salt ions are tiny, and even with cross-flow or tangential filtration, it takes very fine pores (~2 nm or less) and high pressure to create potable water from a saline source of water. The energy required to create that pressure was costly and couldn’t be easily recaptured.

The invention of a specialized ceramic pressure exchanger by Richard Stover allowed desalination plants to conserve and recycle that energy, dramatically lowering the cost to create drinkable water.

Energy Recovery Inc’s (“ERI”) ceramic pressure exchanger made a major impact on the energy requirements to create drinking water using desalination.
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