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My Exclusive Interview With the Inventor of the N95 Mask, Part 2

Last week I had the pleasure of interviewing Dr. Peter Tsai, inventor of the N95 mask. Recently, he was pulled out of retirement to help with the current COVID-19 pandemic…

When we left off yesterday, Dr. Tsai was sharing different ways he’s found to sterilize the masks for reuse.

(If you missed Part 1 of the transcript, simply click here.)

Today, Dr. Tsai shares some tips to build a more effective DIY mask and best practices for mask care…

Ray Blanco: What do you think the best method might be for… your typical hospital isn’t going to have a large hydrogen peroxide vapor sterilization facility. On a nonindustrial scale, what is the best technology, if there is one, for reuse from the ones you mentioned?

Dr. Peter Tsai: Yeah, I tested using hydrogen peroxide. Not vaporous hydrogen peroxide, because I don’t have that equipment. But I boiled hydrogen peroxide, 3% in the market, and after I tested, it did not have the charge decay. You can treat it for three minutes, take it out, get it dry, then you can reuse it, and the virus is killed. I did not have the experiment to see if that peroxide will kill the virus.

But some people indicated that commercial hydrogen peroxide has different rates. Some may work, some may not work. After the experiment, peroxide may have residue on the respirator. So this is the concern using peroxide. OK? Then an article from The New England Journal of Medicine shows that survivability of the virus on plastic surfaces is three days. I proposed a lot if you reuse a respirator up to four days of each use, then the virus already died. They committed suicide. They cannot survive for that long.

Then conservatory speaking, N95 is suggested that you use this up to seven days. In this case, if you go out to do shopping, you stay at home most of the time, you go out for shopping or something two days a week, then you just need to prepare two respirators, right?

Ray Blanco: Right.

Dr. Peter Tsai: These Tuesday, you use number one, Friday, you use number two, the next Tuesday, you use number one again. That is a good way to reduce the consumption of the respirators, right? Because if everyone wears a respirator, then that is a large quantity of the respirators needed, right? The industrial scale to sterilize the respirators, like vaporous hydrogen peroxide… I have the contact with a company that two weeks ago told me they already sterilized, so far, 1 million pieces of the respirators. But if we wear a respirator a day, the USA has a 300 million people, right? That’s a large quantity.

Yeah. You need to do sterilization in home. Rotation of the use of the respirator, I think, is a good way to reduce consumption.

Ray Blanco: Minimum wait, because you say the virus survives on plastic surfaces, about three days, right?

Dr. Peter Tsai: That’s right.

Ray Blanco: You wait four days, maybe just have one, use it only once a week, I guess, right?

Dr. Peter Tsai: That’s right.

Ray Blanco: Maybe seven respirators and just rotate like that, and you can get some more life out of them.

Dr. Peter Tsai: Yeah. Yeah. Conservatively, seven days. Because three days is under the condition of 70 degrees Fahrenheit, 50% relative humidity. Environment, the temperature can be higher or the humidity can be higher and lower, so conservatively, seven days. Higher temperature, higher moisture, days’ survival time of the virus.

Ray Blanco: Dr. Tsai, not all of us have N95 masks. They’re hard to get, which is why you’re working, I know, so much right now. Do you have any advice? People are making cloth masks at home when they can’t get not even the surgical-type masks. Do you have any advice to be able to build a more effective do-it-yourself mask with materials you might have at home?

Dr. Peter Tsai: Yes. You can use a cloth, like a sweater. The efficiency depends on how tight the threads are woven. If the density is high, then it’s difficult for breathing. In this case, you can use very thin fabric that you insert an air filter between. Then when you take off the respirator, you pull out that piece of air filter, then you can wash the cloth mask. OK? You should not use a coffee filter, or you cannot use a paper towel, because coffee filters and paper towels are made of wood pulp. They are not fibers.

Ray Blanco: Right.

Dr. Peter Tsai: They are hydrophilic.

Ray Blanco: OK.

Dr. Peter Tsai: The breathing resistance is very high, because they are very compact. They are hydrophilic, so if there is a droplet that lands on it, then the droplet will spread out. Then it may penetrate through the paper towel or filter. Then it will contaminate your nose or mouth. It does not have a good efficiency. The resistance is very high, so paper towels and coffee filters are not good material to use.

Shop towels can be a material to use because they’re made of fibers.

Ray Blanco: Shop towels, the blue towels that you get at the auto part store?

Dr. Peter Tsai: Yes, yes.

Ray Blanco: OK.

Dr. Peter Tsai: It’s made of fibers, so it has a higher efficiency.

Ray Blanco: Interesting.

Dr. Peter Tsai: Yeah. And they’re made of fibers, so the air resistance is not that high. It is made of PP or PET. Basically, it is hydrophobic. But they need to have an additive, because they are not made for mask application. They apply some kind of hydrophilic agent. In that case, then it is not hydrophobic, it is hydrophilic. The way to test, you put a drop of water and see if it beads up or it just spreads out. If it beads up, then you know it is hydrophobic.

Ray Blanco: Yes.

Dr. Peter Tsai: It’s good.

Ray Blanco: Yes.

Dr. Peter Tsai: Then if it spread out, then probably you can wash it. That kind of fabric is very strong, so you can wash off the agent. Then you can use it to insert between two pieces of cloth for a DIY mask. Then, if you want to have a higher efficiency, the air filter at home, MERV-14, is the best one.

Ray Blanco: Really, I just changed my air-conditioning filters. They were MERV-11. My wife has allergies, so I got her a better filtration level. Hopefully that helps. MERV-14 is the one you want?

Dr. Peter Tsai: It’ the highest efficiency we can get for a home filter.

Ray Blanco: OK.

Dr. Peter Tsai: That MERV-14 has a similar efficiency as this three-fold mask. Similar efficiency, but more problems. It is even more perishable.

You need to put a piece of fabric between two pieces of the cloth. OK? Then after each use, you take it off. Then you wash the cloth mask. Then after the mask gets dry, you insert another one between. It has the efficiency there. Also, these cloth masks can protect. The cloth there can protect the filtration layer. With these kinds of fabric, the filtration layer is in the middle. The outside layer and inside layer are just to protect the inside layer, the middle layer. That is the filtration layer.

Ray Blanco: Fascinating. And as you mentioned, if you’re infected, 95% containment, right? If you have COVID-19, 95%. If you are healthy, it will give you 30–40% maybe, but both people, you’re talking about over 90% reduction in transmission, correct?

Dr. Peter Tsai: 98%.

Ray Blanco: Yes.

Dr. Peter Tsai: If an infected person wears a mask, then 95% of germs will be contained inside the respirator. Wear a mask, OK? Because the mask has a good contact with the mouth and the nose, so the droplet has a direct [contact] with the mask before they’re exposed to the outside.

This is why a mask like this does not have a good efficiency. It has a good efficiency. It does not have a very high efficiency like an N95. It does not have a good edge fit, but still 95% of the germs are contained inside the mask. If an infected person does not wear a mask, the germs are exposed into the air, and then if the healthy person wears a face mask like this, they are only 30–40% protected.

Ray Blanco: Excellent. I want to thank you, Dr. Tsai. Very interesting discussion we’ve had today, and I appreciate that you’re taking some time out of your busy schedule to talk to me and our readers. I wish you the best of luck. The work you’re doing now, who knows, maybe you’ll have another discovery, a better type of way to protect ourselves with the material science that you’re dealing with right now. I’m very grateful for your time, and I want to thank you, and I wish you the best.

Dr. Peter Tsai: Thank you very much.

Ray Blanco: Thank you.

To a bright future,


Ray Blanco

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Ray Blanco

Ray Blanco is the editor of Technology Profits Confidential as well as Breakthrough Technology Alert, FDA Profit Alert, and Technology Profits Daily. Ray has been with Seven Figure Publishing since 2010. In 2019, his closed positions in Technology Profits Confidential outperformed the S&P500 by 50%.

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