Understanding KN95 and Surgical Face Masks

Posted by Hieu Huynh | Jun 03, 2020 | 0 Comments

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Understanding KN95 and Surgical Face Masks

Understanding KN95 and Surgical Face Masks

Each country has its own standards and minimum test requirements for PPE, especially for KN95 and surgical face masks. As face masks became a rare commodity, many of us gladly purchased what we believed to be quality masks. How do you really know the mask's efficiency rating? What do all of these random numbers mean on the packaging? After pouring over hundreds of different KN95 and surgical face mask manufacturing documents, these performance standards became golden. However, be ready to throw in some Physics and Chemistry knowledge to truly understand how they function. Grab your mask packaging and compare the listed standard on the charts below.


Face mask filtration tests generally focus on the Bacteria Filtration Efficiency (BFE). This is where N95 and KN95 masks get their name- they filter out 95% of the available bacteria. Relying solely on bacteria filtration levels in today's world is risky. The bacteria that is being tested is usually around 3.0 µm (micrometers). SARS-CoV-2 aka Coronavirus is only about 0.1 µm.

Not all masks are created equal. For that reason, both the BACTERIA Filtration Efficiency (BFE) and the PARTICLE Filtration Efficiency (PFE) of a mask is important. For example, a mask with a BFE rating of 99 percent at 3.0 microns provides less protection than a mask with a PFE of 98 percent at 1.0 micron. Do not be misled by a high BFE/PFE rating without knowing the particle size that it filters. Always locate the BFE and/or PFE as well as the particle size it is claiming for the mask you choose.

Here is a mask filter magnified, showing the mask fibers and captured particles.

The 0.3 microns size is used in testing since it is the most difficult to capture and is the “most penetrating particle size” (MPPS). Of course, it is easier to trap larger particles. Thankfully, particles smaller than 0.3 microns are actually easier to filter. Yes, that sounds strange, but check out something called the “Brownian motion”. This describes how smaller particle's mass do not float around, being influenced by the air. Instead, these tiny particles will interact with molecules in the air. These tiny particles react as if they are in a pinball machine and dart around erratically. This random motion actually makes them easier to capture.

Once you've verified that your face mask has adequate filtration, please remember that a good seal is just as important to protect yourself. Try on your mask and try to smell strong odors. Make adjustments until you find the most effective fit. Also, take a quick deep breath and ensure the mask sucks on to your face or if you feel air rushing in the sides of the mask. Men, if at all possible, lose the facial hair for the time being. There are so many variables to optimizing face mask protection. All we can hope for is that everyone does their best.

Please contact our office if you have any questions or if we can help you in any way!

Disclaimer. These materials are intended to provide helpful information to medical personnel. They are in no way a substitute for actual professional advice based upon your unique facts and circumstances. This content is not intended or offered, nor should it be taken, as legal or other professional advice. You should always consult with your own professional advisors (e.g. attorney, accountant, insurance carrier).

About the Author

Hieu Huynh

Managing Partner


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