Creating N-99 Masks for All Employees in the Middle of a PPE Shortage

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At Regenexx, we innovate, that’s what we do. However, these past two months we’ve had a problem. How can we keep our patients and employees safe? After all, physician offices are essential in the crisis and should be open. Hence, as an example of how we innovate, this is the story of how we made 3D printed N-99 masks for everyone in our Colorado office and for every Regenexx provider around the country who wants one.

The Problem

You’ve likely heard that we have a severe shortage of N-95 masks for front-line healthcare workers. The “95” means that the mask filters out 95% of all particles, including the small ones that float in the air after someone with COVID-19 coughs. However, physicians and staff who don’t work on the front-line in the emergency room, but who instead work in clinics also need these masks.

While you can find N-95 masks that used to sell for 50 cents for ridiculous prices online, every mask you buy takes one away from an ER doctor, a nurse in the ICU, or a paramedic who can’t control all aspects of their environment in the same way that we can in a private clinic. Hence, the idea of outfitting all of our employees with disposable masks that would rob thousands of units a month from that supply chain didn’t seem right. As a result, we needed a reusable N-95 mask that we could build that wouldn’t impact front-line health workers.

A Solution?

A few weeks ago, my partner, John Schultz, M.D. sent me an email that was put out by a sales rep for a 3-D printer used in dental offices. The 3D file was for a reusable N-95 mask design. Intrigued, I hunted down several more 3D models online. Many of these involved cutting up large fiberglass HEPA filters for HVAC units, which I read could cause serious lung issues for the wearer. However, there was one design that looked like a winner. Someone in the 3-D printer community had redesigned the cut-up HEPA filter mask to use a series 700 Roomba HEPA filter. It turns out that the high-end robot vacuums like to clean your air as they do their thing. Some more online research showed that while this idea on its face sounded nutty, this could really work, as these HEPA filters were widely available, cheap, not made from fiberglass, and this option involved no dangerous cutting of air conditioner filters.

So John Schultz and I began working together to source a local professional 3-D printer company and I bought Roomba HEPA filters for about 90 cents apiece on Amazon. The pro-3D printer worked up a prototype, but the original design online didn’t really fit these cartridges well. In addition, the prototype was of a hard material that was going to be tough to wear all day. Hence, we opted for a rubber-type material and our 3-D printer professional made some edits to the 3D file to get the Roomba cartridges to fit tightly.

Prototypes and Final

The original second-generation prototypes were black, which was pretty off-putting (Darth Vader-esque). Hence, we finally went with medical white. The final product is below (story in the video above):

The Smoke Test

OSHA has a fit test that they use for healthcare workers and others that wear these respirators all day. They use a few different substances, but by far the most noxious of these is a chemical “smoke” irritant made from Stannic Chloride. You basically have a glass ampule where you break open both ends and the air causes the chemical reaction. You place this ampule on one the end of a rubber bulb and push smoke out of the other. How do you know it’s working? I got a small whiff of this stuff and immediately began violently coughing. Hence, if you can expose the person wearing the respirator to the chemical smoke and have them not react, the respirator is working well. That’s in the video above towards the end where you see Dr. Schultz wearing the swim goggles to protect his eyes.

N-99 vs. N-95

HEPA filters are technically N-99 in that they remove 99% of the particles in the air down to 0.3 microns. Given that the small water droplets that hang in the air and contain the virus are in the 1-5 micron range, either N-95 or N-99 will work. However, because these masks use HEPA filters, they are classified as the higher rated N-99.

What Else We’re Doing

Every Regenexx clinic is going above and beyond to protect patients. This is what we’re doing in our Colorado HQ clinic:

Also, if you’re more comfortable staying at home and getting a new patient evaluation or follow-up that’s covered by insurance by using your computer, tablet, or smartphone, we have developed an entire Telemedicine system that allows you to watch a video on self-exam and fill out a form for your Regenexx physician. We have super-specialist physicians standing by all around the country to get you seen:

The upshot? We’ve been working overtime these past few weeks to innovate! We’re also supporting the front-line healthcare workers by reducing our PPE usage as we open our clinics back up to begin to perform elective procedures again!

[If you know a front-line healthcare worker that still can’t get a daily supply of N-95 masks, reach out to us in the Blog comments and I would be happy to supply them the name of our local 3D printer who has these files and who can print these in small, medium, or large. The mask can be made for about $45 and uses 90 cent HEPA cartridges that should last at least a week or more. It can also be sterilized daily with medical grade disinfectants. We don’t make anything off these masks, that’s the 3D printer’s price, so you will pay him directly!

Contact Info to get a mask printed:

Nick Yosha | VP of Sales and Marketing
3D Printing Colorado |
6901 West 117th Avenue, Unit 4 | Broomfield, Colorado 80020
303-466-0900 | [email protected]]

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23 thoughts on “Creating N-99 Masks for All Employees in the Middle of a PPE Shortage

  1. Stacey Kaufman

    You are AMAZING!
    I’m going to reach out to my daughter in law who is an EMT in Lee County Florida and a friend who’s a hospital nurse in Arizona.
    On a side note, would it be selfish of me or smart of me, as a PICL patient, (who will need to be in the airports and spend about 5 hours on a plane to get to you for my scheduled upcoming PICL), to purchase masks for me and my sweetheart who’s traveling with me, so I don’t risk getting the COVID cough and ruining my PICL? I’m 61 and he’s 72. I don’t want to take away from frontline workers, of course, but I am somewhat scared.

    1. Chris Centeno, MD Post author

      The good news about this mask is that it takes nothing from the front line to wear one, so if you want one for personal use, I would go for it. Realize that it may take a week or so to get it printed as it took us a bit.

  2. David Litoff

    I am interested in these masks. We have a supply of surgical masks for our office but would like to get some n95 or similar quality masks. This look very good. If you can send me the name of the 3D printer I would like to order some for my office staff.

    1. Chris Centeno, MD Post author

      Will do David!

  3. Marc Cahn


    I would love to get the name of the 3D printer who makes these masks. I am planning on trying to open in the near future and could use them the link to where you purchased the HEPA cartridges. Thanks. I hope you are doing well.



    1. Chris Centeno, MD Post author

      I will get that to you Marc!

  4. Edith(Edy) Johnson

    Very interesting read. Love that everyone uniting to find best solution.
    Keep on keeping on.

  5. AL Wekelo

    Bravo that’s the way to do it well done!

  6. joseph camporeale

    I am a Pharmacist and would be interested in the name of your supplier
    Thank you

    1. Regenexx Team

      Hi joseph,
      We’ll be posting that info tomorrow.

  7. Paul V Ames


  8. Stacey Kaufman

    Thanks for the info. I spoke with Nick.
    1. Only making medium and large now.
    2. They don’t supply the filters or straps.
    3. I found filters, but where are you getting straps?
    A million thanks!

    1. Chris Centeno, MD Post author

      The straps are large hair ties. Dr. Schultz making a “how to” video tonight…

  9. George Garines

    Dr. Centeno would you please give me the exact Roomba HEPA filters you purchased on Amazon. I went on the website but there are so many filters I don’t know which ones to purchase. I want to purchase the N99 mask but will need the exact filters to fit it correctly.

    Thank you so very much for your Blogs. I read them weekly and they are truly informative. I also want to thank you personally for your work with Regenexx because I am a former patient and it worked miracles on my arthritic shoulders and tears in my shoulder tendons.

    George Garines

    1. Chris Centeno, MD Post author

      Thanks, George! The whole DIY video including the Roomba info is here:

  10. Stacey Kaufman

    I ordered masks and filters but please need the information on which and where to purchase the straps you use.

    1. Chris Centeno, MD Post author

      See the link in the blog

  11. Harlan J. Weiss, MD

    Please get me the information on the 3D printer mask, as all I can get currently get to use in clinic to see patients are disposable KN95 masks at $25 per 5.

    1. Chris Centeno, MD Post author

      Harlan, this is the blog that has all of that info:

  12. Brian Jakubowicz, MD


    I purchased the 3D printed masks about 1 month ago(1 medium and 1 large). When I started wearing them people though I was crazy…now they tell me how cool it looks and ask where they can get it.

    I did however run them through the irritant smoke test with the Roomba HEPA filter and while the masks (medium without weatherstripping and large with) have a good fit, the smoke at about 6 inches away comes right through the HEPA filter. I tried 3 different filters on both masks and the same outcome. Any suggestions?


    Brian Jakubowicz, MD

    1. Chris Centeno, MD Post author

      Yes, we found that taping our filters in with duct tape helped.

  13. Breno Machado


    I live in Brazil and would like to print this mask for my use and of my family.

    Can you send me the STL files?

    Kind regards,


    1. Chris Centeno, MD Post author

      I would get in touch with the person listed in this blog at 3D Printing of Colorado:

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