Comparing KN95s, KF94s, and Mask Fitters


Summary of effective filtration of KN95, KF94, and FTM Mask Brace on 4 subjects
  1. Effective filtration varied by up to 30% between team members depending on who was wearing a given mask
  2. Some people can get good seal with a KF94 (but not everyone)
  3. Ear loop masks like KN95s may not be a good option
  4. Any of these masks is better than no mask. Don’t let anyone tell you that N95s/KN95s/KF94s “don’t work” or “do almost nothing” if they don’t seal well, but do consider using a mask fitter to improve your fit.

What are these masks??


A KN95 is a mask that has been certified to a Chinese standard called GB2626. This standard is similar to the NIOSH N95 standard. You can see a summary of the differences here.


A KN94 is a mask that has been certified to a Korean standard called KMOEL — 2017–64. This standard is similar to the NIOSH N95 standard. You can see a summary of the differences here.

FTM Mask Brace

The FTM Mask Brace is a mask fitter which goes over the outside of a surgical mask to create high quality fit. It has been awarded a Workplace Performance Plus rating by the CDC when paired with an Armbrust USA Surgical Mask and has been validated to improve fit by experts and in published papers.


We tested a PSA KN95 (the original link we used to purchase is no longer available), a Dr. Puri KF94 (L), and an FTM Mask Brace + an Armbrust Surgical Mask (aka a Better Mask High Filtration System).

  1. Normal breathing
  2. Deep Breathing
  3. Turning head side to side
  4. Moving head up and down
  5. Talking (reading a predetermined passage called the Rainbow Passage)
  6. Grimacing
  7. Bending Over
  8. Normal Breathing (again)


Why was the fit so different between masks and between team members? We think there are three reasons:

  • Masks move around when you do
  • Ear-loop masks have bad fit
  • Face shapes aren’t the same

Masks move around when you do

You’ll notice in the full data that performance of each mask varies during each exercise. This is because the mask shifts around the face while the participant is moving.

Ear-loop masks have bad fit. Head straps, ear savers, and mask braces improve fit.

Ear-savers pull ear straps behind the head to avoid pressure on the ears.

Face shapes aren’t the same

Andrew has a slightly angular face with a slightly pronounced nose
Katherine has a soft, oval shaped face with a slightly pronounced nose.
Rod has an angular face with the most pronounced nose of our team members.
Sabrina has a soft, round face and a small nose.

But wait, aren’t KF94s and KN95s required to pass certain fit requirements?

Yes, KF94s and KN95s are supposed to only allow 8% leakage. Leakage is particularly hard to measure because face shapes are so different. What’s the “average face” that is allowed to have 8% leakage? How do you ensure most/all people experience low amounts of leakage?


Sample Size

Clearly, our sample size is quite small. We aren’t making the claim that the FTM Mask Brace is THE solution for universal fit for every person. We’re still working on manufacturing larger braces to pair with larger masks.


There is of course a chance that our KN95 was a counterfeit. After all, the CDC says that 60% of KN95s are fake. NIOSH also revoked approval for dozens of models of Shanghai Dasheng “respirators,” underscoring the prevalence of counterfeit masks.

Well why didn’t you test x, y, z, mask/fitter/filter combination?

Fit testing takes time. If there’s specific data you feel is missing, let us know at and we’ll share the feedback with our team for our next blog post.


As the Delta Variant has become more prevalent, the importance of mask fit is becoming common knowledge. But when you’re picking the right mask for you, don’t just pick your best friend’s favorite mask. Make sure the mask you’re using actually creates a seal with your face.



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Fix The Mask — the technical.

Fix The Mask — the technical.

The latest data and information on the Essential Mask Brace and masks in general.