Filtering facepieces (FFPs) are face masks produced from a whole piece of filtering material, intended to be disposable.
N95 are possibly the most well-known. P95 masks, KN95 masks, KP95 masks, KF94 masks, etc. are very similar.
Many people are working on developing ways to re-sterilizing N95 masks, including open-source recipes for re-sterilizing N95 masks, in response to the expected shortage of N95 masks during the COVID-19 pandemic.
Some of the effective sterilization recipes involve (in no particular order):
- vapor hydrogen peroxide
- ultraviolet light
- bake in a kitchen oven for 30 minutes at 158 degrees F,
- steam the mask with hot vapor from boiling water for 10 minutes
In no particular order:
"Reusability of Facemasks During an Influenza Pandemic: Facing the Flu (2006)" https://www.nap.edu/read/11637/chapter/6
One heat sterilization protocol: bake in a kitchen oven for 30 minutes at 158 degrees F (70 degrees C). "European certification requires a [N95] mask to be able to withstand 158 degrees Fahrenheit (70 degree Celsius) for up to 24 hours."
The ultraviolet sterilization protocol: ultraviolet germicidal irradiation (UVGI) has been successfully used to decontaminate N95 respirators exposed to the influenza virus. The upper limit for repeated disinfection cycles is set by physical weakening of the N95 mask material (tears easily) and not by a loss in filtration capacity. The respirator straps retained most of their strength; weakening of the body of the N95 mask is the limiting factor in UVGI and not the weakening of the straps.
hydrogen peroxide sterilization
The hydrogen peroxide sterilization protocol: decontaminated N95 respirators over 50 cycles, limited by the elastic straps showing degradation. disperse 480+ppm Hydrogen Peroxide vapor, gassing for 25 minutes and dwell for 20 minutes. Then introduce fresh air, and wait for 4 hours for the hydrogen peroxide to convert into oxygen and water.
Fabric face mask sterilization
"Cloth or fabric face masks for home use can be sterilized by washing them in the washing machine." -- https://www.cnet.com/how-to/homemade-face-masks-coronavirus-and-the-cdc-heres-everything-you-need-to-know/
However, some people say this ruins the static electrical charge on the microfibers in N95 masks, making them much less effective.
https://www.reddit.com/r/Coronavirus/comments/f45vkj/a_great_article_on_how_you_can_sterilize_a_n95/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4699414/ https://www.ncbi.nlm.nih.gov/pubmed/25806411 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4699414/ https://www.ajicjournal.org/article/S0196-6553(18)30140-8/pdf https://www.peakprosperity.com/forum-topic/can-uv-light-disinfectant-box-kill-viruses-off-n95-mask/ https://www.nebraskamed.com/sites/default/files/documents/covid-19/n-95-decon-process.pdf https://www.cdc.gov/niosh/nioshtic-2/20045956.html https://www.wbur.org/commonhealth/2020/03/27/umass-memorial-disinfects-masks-ultraviolet-light
"tabletop UVC germicidal light" https://www.youtube.com/watch?v=aaVnAO1Vv-k
hydrogen peroxide sterilization
https://www.safety.duke.edu/sites/default/files/N-95_VHP-Decon-Re-Use.pdf via https://www.cnn.com/2020/03/27/health/n95-respirator-rewear-coronavirus-duke-trnd/index.html https://hackaday.com/2020/04/02/fda-says-ppe-can-be-reused-after-trip-through-shipping-container-decontamination-system/
"Battelle Critical Care Decontamination System" https://imgur.com/gallery/rVinlrX https://www.sages.org/publications/tavac/battelle-ccds/ is a vaporized hydrogen peroxide system.