Masks are an integral component of personal protective equipment, especially in the case of infections that may be contracted through a droplet or airborne transmission. As the Covid-19 pandemic has shown, this holds true for both healthcare workers and the general public.
Generally, the effectiveness of a mask is largely dependent on the percentage and size of particles that it can filter and upon how well it fits the facial features of the wearer to ensure that there are little to no spaces or gaps between the face and the mask. The additional important element to consider is the fluid/droplet resistance of the mask. Both of which offer high levels of resistance.
Particularly, because of the better fit, and respiratory protection offered by KN95 and N95 masks, they are preferred over surgical masks, which, on the contrary, only offer protection against particulate matter and act as a barrier against fluids(1).
How do the N95 and KN95 respirators differ
Primarily, the N95 masks are according to the US standards of respirator masks and governed by NIOSH; the KN95, on the other hand, are according to the Chinese standard. KN95 is the Chinese equivalent of the N95 mask. Because of the shortage of N95 respirators early in pandemic, especially for medical personnel in high exposure environments, the import of KN95 masks had to be authorized under Emergency Use Authorization (EUA).
However, these respirators are not entirely the absolute same. The following compares the two respirators.
- Filter Layers: Both N95 and KN95 masks usually have five layers for the filtration of airborne particles. However, the layers in N95 masks were found to be at least eight times thicker than those of KN95, thus possibly offering higher filtration ability. However, the thickness of material itself is not the most conclusive indicator of filtration ability and much depends on the independent testing of each mask. There are many KN95 masks that have been tested to filter as much or more than N95 masks. The quality of the material itself, varying by each manufacturer, is the ultimate factor in its filtration efficiency. (2)
- Performance Of Filters: The N95 masks have demonstrated filtration efficiency of a minimum of 95% for particles sized 0.3 microns. (3) As opposed to this, National Institute for Occupational Safety and Health (NIOSH) approved KN95 respirators have shown efficiencies of lower or greater than 95% when compared to other approved respirators for the most penetrating particle size. (4) Both N95 and KN95 masks are also very effective in limiting infection from harmful airborne particles.
- Flow Rate: The breathability of both the respirators on comparison shows that the N95 respirator allows an inward flow rate of 85 L/min during inspiration (5) which is comparable to that of the KN95 respirators. The exhalation resistance, in turn, is also comparable at less than 245 Pa for KN95 and less than 250 Pa for N95. Again, this largely depends on the quality of manufacturing and buying KN95 masks only from trusted, vetted suppliers.
This comparison essentially demonstrates that the filtration ability of the KN95 respirators, even those that are NIOSH approved, is comparable to that of the N95 respirators. The main difference being the fact that N95 masks have dual ear bands and KN95 masks have an earloop design. KN95 mask is generally much more comfortable to wear for extended periods of times.
Not only is the KN95 essentially is similar to the N95 respirators in its ability to filter out smaller particles efficiently, but the existence and wide availability of counterfeits is more of a problem that makes these respirator masks largely unreliable for use, especially for health care workers who need additional protection. Therefore, it cannot be stressed enough that purchasing from reliable and trusted supplier is essential in ensuring that you receive the protection you expect.
For the general population, and in low-exposure areas with decreased risk of transmission of infection, the use of either KN95 or N95, if available, may be suitable and inherently superior to the protection offered by surgical masks or masks made of cloth.
- Center for Devices, Radiological Health. N95 Respirators, Surgical Masks, Face Masks, & Barrier Face Coverings [Internet]. 2021 [cited 2021 Nov 14]. Available from: https://www.fda.gov/medical-devices/personal-protective-equipment-infection-control/n95-respirators-surgical-masks-face-masks-and-barrier-face-coverings
- Yim W, Cheng D, Patel SH, Kou R, Meng YS, Jokerst JV. KN95 and N95 Respirators Retain Filtration Efficiency despite a Loss of Dipole Charge during Decontamination. ACS Appl Mater Interfaces [Internet]. 2020 Dec 9 [cited 2021 Nov 14];12(49). Available from: https://pubmed.ncbi.nlm.nih.gov/33253527/
- Qian Y, Willeke K, Grinshpun SA, Donnelly J, Coffey CC. Performance of N95 respirators: filtration efficiency for airborne microbial and inert particles. Am Ind Hyg Assoc J [Internet]. 1998 Feb [cited 2021 Nov 14];59(2). Available from: https://pubmed.ncbi.nlm.nih.gov/9487666/
- Brochot C, Saidi MN, Bahloul A. How Effective Is the Filtration of “KN95” Filtering Facepiece Respirators During the COVID-19 Pandemic? Annals of work exposures and health [Internet]. 2021 Apr 22 [cited 2021 Nov 14];65(3). Available from: https://pubmed.ncbi.nlm.nih.gov/33125464/
- Cho KJ, Reponen T, McKay R, Shukla R, Haruta H, Sekar P, et al. Large particle penetration through N95 respirator filters and facepiece leaks with cyclic flow. Ann Occup Hyg [Internet]. 2010 Jan [cited 2021 Nov 14];54(1). Available from: https://pubmed.ncbi.nlm.nih.gov/19700488/