What’s The Difference Between N95 and KN95 Masks?

Due to the shortage of N95 masks for healthcare workers and first responders, the Center for Disease Control (CDC) has authorized the use of KN95 masks in place of N95 masks for the response to COVID19. With such similar-sounding names, it can be confusing to understand the difference between N95 and KN95 masks. What are KN95 masks, and are they the same as N95 masks? In this article, we will explain the difference between KN95 masks and N95 masks, and how we can clean them.

N95 Respirator Masks

N95 respirator masks follow the United States National Institute for Occupational Safety and Health (NIOSH) standard, they are the most well-known respirators which filter up to 95% of particles and create an air tight seal around the face. These type of respirator masks are not specifically regulated by the FDA, rather they are regulated by the CDC and NIOSH. 

KN95 Respirator Masks

KN95 masks follow the Chinese government regulation GB2626-2006 and are rated to filter 95% of particles. In April of 2020, in order to help expand the availability of general use face masks for the general public and particulate filtering facepiece respirators for healthcare professionals during the COVID-19 pandemic, the FDA issued guidance authorizing the use of KN95 masks as suitable NIOSH alternatives under certain emergency circumstances (Source:FDA https://www.fda.gov/medical-devices/personal-protective-equipment-infection-control/faqs-shortages-surgical-masks-and-gowns and FDA https://www.fda.gov/media/136449/download).

On May 7th of 2020, the FDA updated the April guidance and issued further guidance limiting the use of certain KN95 masks as suitable NIOSH alternatives in a healthcare setting (Source: FDA https://www.fda.gov/media/136663/download).

What are the differences between N95 and KN95?

Both ratings require masks to be tested for filtration efficiency at capturing salt particles (NaCl). Both are tested at a flow rate of 85 L/minute. However, there are some differences between N95 and KN95, highlighted here.

Most of these differences are small and would be uninteresting to the average mask user. However, here are the key differences:

1. To be certified as a KN95 mask, the Chinese government requires the manufacturer to run mask fit tests on real humans with ≤ 8% leakage. The N95 mask standard does not require manufacturers to run fit tests.

This does not mean that fit tests aren’t helpful. Many hospitals and companies require their workers to be fit-tested. However, those are requirements of companies themselves, not for the US NIOSH certification on the mask.

2. N95 masks have slightly stricter requirements for pressure drop while inhaling. That means they’re required to be slightly more breathable than KN95 masks.

3. N95s also have slightly stricter requirements for pressure drop while exhaling, which should help with breathability.

How do we clean them?

Even though N95 and KN95 are recommended to discard after one-time use, there are ways to clean them properly so we can reuse them for a few more times.

Unlike a cotton face mask where we use water, detergent, or alcohol disinfection, it's recommended to use UV light disinfection or steam the mask with hot vapor from boiling water to clean the mask. Why? Both N95 and KN95 are based on the principle of electrostatic adsorption. The melt-blown cloth of the mask is filled with permanent static electricity. The small molecules of each filter cloth are covered with a lot of high current (lots of electrons moving through a cross-section of conductor per second), and small particles will be adsorbed after passing through. If you use water, detergent, or alcohol disinfection to clean the mask, the static electricity will disappear, and the filtering effect will be greatly reduced. It is also recommended to clean it after each use.

What is UV Light Disinfection?

UV light offers a potential option that can be a safe and cost-effective way to sanitize masks, if the right amount of light, for the right length of time, is dosed by a well-understood optical device.

UV light penetrates the mask and works by damaging the molecular bonds that hold together the nucleic acids (DNA or RNA) of the viruses or bacteria and stops them from infecting and/or replicating within a human cell. The UV light used is shortwave and cannot be seen by the human eye so to effectively kill the virus requires an understanding of the irradiance—amount of light energy or UV intensity—the length of time the mask is dosed, and knowledge of the UV optics of the disinfection device. 

References:

1. Admin. “KN95 Mask vs N95 Mask – Current FDA Guidelines Surrounding COVID-19 Pandemic.” Accumed, 8 Apr. 2020, accumed.com/blog/kn95-mask-vs-n95-mask/.
2. “Introduction to UV Disinfection.” TrojanUV, www.trojanuv.com/uv-basics.
3. “KN95s: COVID-19: Oklahoma State Department of Health.” KN95s | COVID-19 | Oklahoma State Department of Health, coronavirus.health.ok.gov/kn95s.
4. Letzter, Rafi. “Doctors Scramble for Best Practices on Reusing Medical Masks during Shortage.” LiveScience, Purch, 24 Mar. 2020, www.livescience.com/sanitizing-medical-masks-for-reuse-coronavirus.html.
5. TalhelmThomas, Thomas, and University of Chicago Booth School of Business. “What's The Difference Between N95 and KN95 Masks?” Smart Air, 9 June 2020, smartairfilters.com/en/blog/whats-the-difference-between-n95-and-kn95-masks/.
6. “UV Light Method Shows Promise for Sanitizing N95 Masks.” StackPath, 8 Apr. 2020, www.bioopticsworld.com/biophotonics-tools/article/14173690/uv-light-method-shows-promise-for-sanitizing-n95-masks.