My Exclusive Interview With the Inventor of the N95 Mask, Part 1
There’s been a lot of misinformation in the press about COVID-19.
Especially when it comes to masks.
It’s more important today than it has ever been to fight misinformation and poor logic.
That’s why I was thrilled to have the chance to sit down with Dr. Peter Tsai, inventor of the N95 mask.
Last week, I shared a few details about my conversation with Dr. Tsai. (If you missed it, click here.)
Today, I’m pleased to bring you Part 1 of the transcript of that conversation. Let’s jump right in…
Ray Blanco: Hi, everyone. This is Ray Blanco, your editor and lead analyst here as usual. Thanks for tuning in. As you know, we’ve been covering COVID-19 here at Technology Profits for months, but these days, there’s still a lot of conflicting information about how the virus disseminates, including how we can protect ourselves doing things like using face masks.
But today I have a special expert guest on this subject. His name is Peter Tsai. He is a material scientist and engineer, and he invented the filtration fabric that is used inside the N95 mask. He made this invention 25 years ago, and it has become very important today.
How are you doing today, Dr. Tsai?
Dr. Peter Tsai: I’m very good, thank you.
Ray Blanco: Excellent. Could you tell us a little bit about your own personal background and how your research led to the creation of the N95 mask?
Dr. Peter Tsai: Yes. In 1980s, I joined a textile group at the University of Tennessee. They had a microfiber process. That is melt blowing. That is a process to make microfibers for different applications. And one of the major applications is for an air filter. So at that time, we thought that in addition to the new chemical mechanism to attract the particles, if we could put the charges into the fibers, that would increase the efficiency by electrostatic attraction and it was true. After our experiment, we found that the charged fabric can have 10 times higher efficiency than the uncharged one.
So after the N95 specification that is U.S. standard was going to be issued in 1995. That is the year, 1995. This has nothing to do with N95, OK? Then companies approached us to see if this technology could meet the requirement for N95. Now we found that this technology exceeded the requirement for N95, so they licensed our technology and they used our technology to make the charged microfiber fabrics for the material for N95.
And by the way, N95, the “N” means not oil-resistant. This respirator is used not in oily environments. Like spray painting. All these operations. So this respirator is not suitable for that application. And “95″ means the efficiency of the submicron particles. In this case, we use 0.07 microns of the particles to do the testing. Then the efficiency needs to be higher than 95%. That is called N95.
Ray Blanco: Fascinating. This material, what is the material itself? How is it made?
Dr. Peter Tsai: The material is made by a process called melt blowing. Melt blowing is to make microfibers directly from the polymer resin. In this case, this polymer resin, it’s PP. Polypropylene. We melt the polypropylene in [another substance]. Then, we use extrusion force to force the melt through an orifice, a small hole. Then each hole makes a fiber. For example, in the industrial scale, usually, the width is 1.7 millimeters wide. It has about 1,500 holes there; 1,500 fibers are made simultaneously. Then, we use that hot air moving at high speed to attenuate to the fiber. Attenuate means to pull in the drape, the fibers to make the fiber thinner, and thinner. This is a way to make microfibers. Then the microfibers bend on a corrector. It makes the wave. That’s a microfiber fabric. The process is called melt blowing because we melt the polymer and then we blow the fibers. It’s called melt blowing.
After that, we do electrostatical charge in all the fabric.
Ray Blanco: What you mentioned is the very special property of it that helps boost its filtration capacity.
Dr. Peter Tsai: Yes. Two characteristics. One is because it’s a microfiber. A microfiber has higher surface area, even the same weight. Then, electrostatic charges the inside of the fiber. It improves the efficiency by 10 times. In this way, it can meet the efficiency we need, and it does not adversely increase the residual drop. That means that reusability is still there. For a respirator, you need to need to have the efficiency, but you need to have comfort when you wear the respirator. It needs these two characteristics.
Ray Blanco: Dr. Tsai, how durable is this electrostatic effect? I mean, my personal example, back around 2014, I bought a box of 3M N95 masks. As you probably remember, a lot of people were worried about an Ebola outbreak at the time. They say Ebola was not airborne, but you never know. Ha, ha! New evidence could emerge. I did buy a box. This is about six years ago. Do they still retain this charge for this amount of time at ambient room temperature?
Dr. Peter Tsai: Yes. If they were properly made, the charges should be there for a long time. You check the box. It has a warranty of shelf time. Usually, it says five years. But some of my customers say nine years. If it’s not made properly in terms of material, process, charging, charging environment, everything, then the charges can go in a short time. In that case, they cannot put five years or 10 years as a shelf time for warranty. OK? Because for N95, nine of us audited the quality, even in the market or in the shelf so they have the technology to retain their charges. If in instruction manual, you see the shelf time is five years’ warranty, then it should be good for at least five years. From my experience, I created the charge decay for 15 years, then I formed it up even after 15 years. The charges are still there, and the efficiency is still there, higher than 95%.
Ray Blanco: Excellent.
Dr. Peter Tsai: So if they are authentically made, then it’s good. You need to read the instructions.
Ray Blanco: We’ve had a lot of people with conflicting information on the internet. A lot of people don’t have access to N95 masks, so they’re using the surgical masks or they’re making cloth masks. Like for example, surgical masks, I would not expect them to have the protective benefit of an N95 because I assume the filtration efficiency is lower. Does that mean that they should not be worn or they’re a waste of time?
Dr. Peter Tsai: No. There are basically two types of masks. When we say mask, usually, we say this kind of free form, the mask, or cloth mask. OK? Then sometimes people call this a mask, but specifically, this is a respirator. The difference is a mask does not have a good edge fit. When you wear it, a lot of air comes in from other side. That is a mask. The respirator has a good edge fit, so air does not come in from the side if you wear it properly. Then, in addition to that, masks has less efficiency than a respirator. These kinds of free-form masks are made out of vent-open fabric. These are higher efficiency than the cloth mask. But the cloth mask is washable. This is made out of vent-open fabric, so it’s not washable. There are two types of these free-form masks. One is for general use, does not have specification. Nobody regulated it. A medical face mask is then FDA regulated. There are specifications there.
A medical face mask is better than general-use face mask, even if they have a similar shape. But if they are masks, then they don’t have a good fit at the edge. About 40–60% of the air comes in from the side. But the function of a face mask of this type, or a cloth face mask, is to contain the virus inside the respirator for an infected person. Basically, 95% of the virus is contained. This is why everyone needs to wear a mask. If the infected one does not wear a mask, if you wear this kind of mask, then you are only about 30–40% protected. This is why you said this is good for protecting against the virus if the infected person does not wear it. Then it does not have a good efficiency to protect you. You are only 30–40% protected. But if everyone wears, then you are 98.5% protected. For the health workers, they need to wear N95 because this one has a good edge fit, so air does not come in from the side. This one has much higher efficiency than the mask.
Basically, these kinds of respirators are sufficient enough to protect the workers in the hospital. For general use, we just need to use this. When everyone wears, then we are 98.5% protected. In addition to that, we need to do combination of other things to fully protect us, like a screening, testing, isolation, hand washing, social distance.
Ray Blanco: Right.
Dr. Peter Tsai: OK, so a mask is just one way of defense. Not the whole thing. But it’s very important.
Ray Blanco: And combined, you cut down on transmission with each measure so that all put together you really reduce transmission with mask use, with social distancing, with washing your hands, of course, and everything like that.
Dr. Peter Tsai: Yeah. Testing, isolation, then the transmission reduces to zero. The problem is many people do not follow CDC guidance. That is something everyone needs to know.
Ray Blanco: Dr. Tsai, I hear that not very long ago, you were called out of retirement and that you’ve been very busy, you’ve been working some very long days. I hear 20 hours a week working on N95 masks because we’ve had a critical shortage of mask production, and I was interested in knowing what you were doing, and what you have perhaps discovered in that time.
Dr. Peter Tsai: Basically, longer than 16 hours a day. Sometimes. Sometimes 20 hours a day, not a week.
For example, the shelf lifetime, as you mentioned just now, how long it can be stored before we use and how long it can last during the time that we use, and see if they can resist the charge to decay by a filament or heat, or ethanol, or alcohol, something like that. I had experience with that already. So I felt obligated to provide information I have known for all my 35 years of experience. For the virologist to study using possible ways to do a sterilization for reuse of the respirators in this time of demand. Then after that, a group of people, many groups of people, in the world doing the study, we finalized several ways to sterilize the N95 to reuse. At the same time, I help out Oak Ridge National Lab to convert their production line to make microfiber fabrics for N95 material.
The same way, they teach the industries to convert their lines into making microfiber fabrics. I have several existing customers, and I have them to do the production in full capacity. Also several new companies want to install the machine. They want to set up the conversion machine to make respirators. They need to have the knowledge, what kind of fabrics to make, what kind of fabric to choose to make, what kinds of respirators or masks. So during this period of time, in addition to that, a lot of questions asked of me about how to sterilize the mask and how to set up a machine. And also the media asking me the questions in order to educate the people so everyone has the knowledge about respirators and the performance of respirators, how to wear them, how to keep them, how to [don] them. Everything together to make it be easy. But I’m happy to do it because this is an opportunity for me to serve the community.
If there’s something I can’t do, I did not do, that I will regret for the rest of my life, right?
Ray Blanco: Right.
Dr. Peter Tsai: But if I can have the opportunity to help people to save lives, then that will be a good memory for the rest of my life after my retirement.
Ray Blanco: I think everybody in the country, in the world, appreciates that we have scientists and engineers like you working on these problems.
Are there actual methods, good methods, for sanitizing these masks that allow reuse and don’t destroy the electrostatic properties of the fabric?
Dr. Peter Tsai: Yes. There are four methods validated by the NIH. It is if we reverse hydrogen peroxide, heat, dry heat, at 70 degrees for 60 minutes, and 70% ethanol. Reverse hydrogen peroxide is in industrial scale, so you need to have the equipment, very precise equipment, to use.
UVC, there are some concerns it will be uniform to sterilize the whole piece of the fabric. It may only sterilize the surface, because it may not penetrate the first layer. There’s a severe concern there. 70 degrees Celsius for 60 minutes. You need to have a way to control the temperature in a great range. From 70–75 degrees Celsius. The kitchen oven, from my experiment, uses an infrared thermometer. The temperature range is too big. It drops very low, and then when it’s kicked on, temperatures go up too high. Then if you set my kitchen oven temperature, the lowest temperature is 170 degrees F. That’s about 75 degrees C. That is OK. But in other settings, if you put it on, let’s say, 170 but it already went down to 55 degrees C, if you put that tire on the upper position of 170 degrees C, it went up to 190, or 200, or 210, something like that.
The oven is an oven for you to cook and does not have a good control in the temperature range. So if you really want to use the heat, then you need to have a good control of the temperature range, between 70 degrees and 75 degrees.
Ray Blanco: Isn’t that the high heat, since it’s polypropylene, right, plastic? Is it that it melts it, or is it that it distorts it and then it no longer fits properly?
Dr. Peter Tsai: No. The melting temperature of PP is 160 degrees Celsius.
So if you treat it at 70 degrees C, then it does not hurt. But the respirator has a composition of different materials under the PP. Other materials like outer layer or inner layer may not resist the temperature too high. You need to check after your treat, see if you it altered the shape, as you said. Then it no longer has a good fit, so you need to check. For three, or four, or five times, maybe OK, but after six or seven, eight times, then the shape may be severely changed. In that case, you don’t have a good tight fit. You cannot use it anymore. OK? If the shape does not change, then it can be sterilized for 10–20 times, because from our experiment, 70 degrees C dry heat for 24 hours does not have the charge decay. It’s a very insignificant charge decay from 99% to 98.5%. The efficiency of N95 just needs to be over 95%. It is still way above the efficiency required for N95.
Then ethanol can sterilize the virus, but ethanol will tear charges. You can use ethanol to sterilize the respirator, but not for reuse. It’s for disposing. After you sterilize it, then you dump it into the trash bin, so the janitor can pick them up when they collect garbage and they will not get infected. That’s the purpose of sterilizing using ethanol…
Keep an Eye out Tomorrow!
Tomorrow I’ll share Part 2 of this interview. In it Dr. Tsai reveals one everyday item you can use to boost the effectiveness of your mask. (And a few that have been rumored to but won’t.)
Stay safe (and healthy) out there!
To a bright future,