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What data is there on the DIY Surgical Mask Brace?

This solution has not yet been tested to the N95 standard, CDC/NIOSH 42 CFR 84. We are in line at AFFOA to get this testing completed. While we wait, we're being proactive about our testing. There are two main metrics that are required for good mask function:  fit and filtration.

Fit: The fit of N95s is tested with a quantitative measurement system called a Porta Count Pro+. The passing score on this system for an N95 is 100 or above. The University of Pennsylvania Perelman School of Medicine, and another American medical school have piloted studies using this system with our DIY Surgical Mask Brace. All physicians tested so far have passed the fit test with a score over 100 when properly tensioning the side bands. Check out the latest published data here.

Filtration: This solution utilizes ASTM-Level surgical masks, which are held to a filtration efficiency at 0.1 micron particles of 95%. How does this compare to 42 CFR 84? For more detail, check out our blog post.

Because initial data for fit is excellent, and the filtration is good, we expect that this solution will make a difference to the many people who do not have access to N95s, but do have access to surgical masks.

Can I use cloth as an alternative to a surgical mask?

Cloth can be dangerous. An effective filter for COVID-19 is able to block out COVID-19 sized particles. How big are those particles? Research suggest that the hardest particle size to capture is 0.3 microns. If you took 250 of those particles and stacked them in a row, that would be equal to the diameter of one human hair. These particles are not visible to the naked eye.

How do you check if your material is a good choice? Try #TheWindowTest. If you hold most cloth up to a light, you’ll notice that you can see pin holes of light coming through. If you can see the pin holes of light with your naked eye, then COVID-19 particles can get through.

In addition to the fabric’s ability to filter, you must also consider stretchiness, breathability, and water resistance. If a fabric is too stretchy, the pin-hole size can increase while you're wearing it, making it an ineffective filter. If it’s not breathable enough, our health care workers won’t be comfortable while wearing them and won't be able to do their jobs effectively. If not resistant to splashes of water (like a paper filter, for example), the filter could degrade, or, via capillary action, virus-laden particles could travel from the outside of the mask to the inside of the mask.

Don’t we need an Exhalation Valve as seen on the N95 masks?

This is a misconception, many people think the Exhalation Valve is meant for filtering particles, but actually the valves are used only to improve venting of the mask so that they are less stuffy and more comfortable to wear. Some N95 masks do not have the valve and that’s okay, because it is not required for filtering.

Can I use the Surgical Mask Brace for small faces?

The DIY Surgical Mask Brace can be modified to fit a number of different face sizes and shapes - all you need to do is find a central rubber band thickness and diameter that creates a good seal for you.

The V2 Surgical Mask Brace can also be modified to fit a number of different sized faces. Simply print the design out at 50%-90% scale.

Once you have a Surgical Mask Brace attached to your face, perform a seal check as recommended by the CDC. Cover the area within the rubber band completely with one or both hands and exhale sharply. If you feel leakage, there is not a proper seal. Readjust the brace to improve the fit and repeat the test.


Is a Surgical Mask + a DIY Surgical mask brace equal to an N95?

Not yet tested. The surgical mask brace design has not undergone the CDC test method outlined in 42 CFR 84, which qualifies N95 respirators.

Do we have to use ASTM Level 1 masks?

Fix the Mask recommends using ASTM Level 1, Level 2, or Level 3 masks with our design because those are standardized to have a high particle filtration efficiency. ASTM Level 1 guarantees sub-micron particulate filtration efficiency at 0.1 microns is ≥95%. ASTM Level 2 and 3 guarantee sub-micron particulate filtration efficiency at 0.1 microns is ≥98%.

Can you re-use a surgical mask?

Fix The Mask does not recommend re-using surgical masks.

Can my hospital participate in a fit test clinical study trying the DIY Surgical Mask Brace?

Please reach out to us at for our test protocol.


What testing standard is required for COVID-19?

No solution on the market today is guaranteed to protect against COVID-19, even N95-level masks. That said, some research papers suggest that viruses can be transmitted through aerosolized particles generated from coughs. The general consensus is that for a mask to be effective, it needs to filter out particles of this size.

What is the difference between ASTM, CDC/NIOSH, and FDA testing?

The CDC has a really helpful table published here. For a detailed break down, check out our blog post here.

Will European-standard or Chinese-standard masks work too?

Fix the Mask only recommends using ASTM Level 1, Level 2, or Level 3 surgical masks. The USA test standards differ from European test standards which differ from Chinese test standards. For a helpful summary, see this table put together by (source).


Why are you using surgical masks?

Surgical masks are regulated, and they are available.
Surgical masks rated to ASTM F2100 Level 1 or above (source) are rated to a sub-micron particulate filtration efficiency at 0.1 microns of ≥95%.
For every 1 N95 mask made, 300 surgical masks are made, according to the National Development and Reform Commission.

Why can't manufacturers just make more N95 masks?

The material required to make N95s is in short supply. What's more, N95s take a long time to make. They are all domed/duck-billed in shape, meaning many additional process steps are required to get from the flat material sheet to the final product. Chinese manufacturers are struggling to keep up with the demand with their current machines. They are trying to build more, but it takes time. (source).

Surgical masks, on the other hand, are simply heat-pressed laminated sheets. Surgical masks are a much more efficient use of our limited material supply (source).


What size rubber bands should I use?

For the central seal, Fix the Mask recommends using #32 or #64 for average sized faces, and #31 for small faces. For the side bands, #33 can be used around the ears, or safety pinned behind the head.

How does this solution solve the shortage?

ASTM-level surgical masks are currently being under utilized at hospitals because the leakage on the side exposes the wearer to potential COVID-19 particles. A strong seal makes those usable. Not necessarily N95 level, but certainly better than nothing.

At the end of March (peak pandemic for many parts of the world), China was making 200 million masks per day, but only 600,000 were N95 masks. N95s take longer to make because of they need to be formed into a shape that fits the face. Surgical masks, on the other hand, are just cut out of square sheets. N95 masks are a much less time-efficient use of our strained supply of melt blown fabric. If we push more demand for good quality filtration sheets, like ASTM surgical masks, we can fix the shortage.

Where do I buy rubber sheets?

Fix the Mask recommends or Fix the Mask does not receive any money at all in exchange for recommending these companies. We recommend them only because they supply good material in a reasonable time frame.

The DIY Surgical Mask Brace rubber bands on my ears keeps slipping off, what should I do?

What’s your teams background?

We are a group of ex-Apple and MIT mechanical engineers, a health startup serial entrepreneur, a marketing lead, and have been helped by many skilled individuals in various fields. See the 'Our Story' page here.


My question wasn't answered, can I talk to someone?

Absolutely! Reach out to us at and we will be happy to help.