Proper disinfection and decontamination of N95 or KN95 face masks is tricky business. You need to inactivate the virus without compromising the filtration and fit of the mask.
Other than the CDCs recommendations for extended use and reuse, there isn't much "peer reviewed" information available on decontamination of N95 face masks.
That doesn't mean there isn't any…
The Society of American Gastrointestinal and Endoscopic Surgeons list a few key principles for effectively cleaning face masks.
The method must sufficiently inactivate the viral load on the mask.
The mask cannot be soiled (bodily fluids, makeup).
The filtration capacity and ionic charge must be preserved as much as possible.
The fit of the mask cannot be compromised.
Several decontamination methods for inactivating the COVID-19 virus exist that show promise.
Decontamination Using Vaporized Hydrogen Peroxide
Researchers at Duke Health recently looked into sterilizing N95 face masks by means of vaporized hydrogen peroxide. Using "specialized equipment" in their biocontainment laboratory, they successfully decontaminated N95 face masks.
The vaporized hydrogen peroxide was able to permeate the mask layers and kill microbes without deteriorating the mask.
Not every hospital has this technology available to them unfortunately, but there are other potential methods of sterilization below.
Keep in mind none of these methods are endorsed by the CDC or the mask manufacturers; however, due to the severity of the current crisis may be helpful.
Decontaminating N95 Masks Using Heat
One study performed by the University of Tennessee performed a variety of tests using heat and suggested that heating a mask at 70C for 30 minutes can provide decontamination while preserving filter integrity.
Decontaminating Masks Using UV-C Light
Another method, already in use by some hospitals, uses UVGI (Ultraviolet Germicidal Irradiation) to kill Corona Viruses. In a recent, non-peer reviewed study, N95Decon found promising data to indicate that UV-C light can effectively render COVID-19 inactive.
This was performed under specific dosing measurements and adequate light penetration onto the surface material, or FFR, of the masks.
This seemed to be one of the more promising methods provided the entire surface of the mask and straps could be dosed with adequate amounts of UV-C.
However, N95Decon admits that "UV-C and other deactivation approaches should be viewed as risk mitigation for extraordinary circumstances rather than complete decontamination."
A key takeaway from this study was the ability to effectively bathe all exterior surfaces of the mask with UV-C light—previous studies showed residual traces of virus even after decontamination had been performed, likely due to limited exposure of the entire surface area.