I was contacted by a hospital and was asked to help them come up with a way to sterilize N95 masks. They believe there is a 2-3 week gap that they must cover before additional N95 masks are available. They have been experimenting with UV light but that seems to break down the mask material.
Looking for experts in the field of elastomers and UV stabilization/sterilization.
Please respond to this post or DM me if you have expertise.
Thanks.
70c industrial-scale curing or dehydration ovens maybe more available - equally effective based on the Stanford study above.
Sample process protocol for UV sterilization is linked from here
This is the article the hospital that contact me is working from. I’m trying to get up to speed and assist where I can. Thanks.
Rumblings today that the Nebraska procedure uses too low a dose, other sources are looking at 2-5 J/cm^2 over 1-15 minutes
In the meantime, this is an excellent summary of research on UVGI dosage and other sanitization methods prepared by a doctor at VGH, whom we’ve been consulting with: PPE recycling in a pandemic - Google Docs
If you don’t have UV sources available or confirmed in the mail, I’d architect it as a room-sized oven with recirculating fans - taking advantage of larger volume to do larger batches, since the limiting factor is heat diffusion into the material and recirculating fans and multiple locations of thermometers/thermocouples will let you assess minimum room temperature. )
Ran across the high level FDA regulations for UV disinfecting chambers if you need some bedtime reading
https://www.ecfr.gov/cgi-bin/text-idx?SID=354d8b0fcc9bacaf08ef6e9d25250208&mc=true&node=pt21.8.880&rgn=div5#se21.8.880_16600
Thanks. Best of luck in your efforts.
There’s a new method that was just announced by Duke Health. They’re using an existing decon technology, vaporized hydrogen peroxide, to decon N95 masks. The good things about what they’re doing are that 1) many hospitals already have this equipment for deconing biocontainment labs and sterilizing places where persistent bacteria and viruses can linger, 2) it’s non-toxic once the decon cycle is complete since hydrogen peroxide breaks down to water and oxygen, and 3) it decons at least as well as other methods (like the heating technique Stanford announced) and it doesn’t affect the materials or the fit of the masks, which is crucial for their reuse multiple times. Here’s the article from Duke Health:
https://corporate.dukehealth.org/news-listing/duke-starts-innovative-decontamination-n95-masks-help-relieve-shortages?h=nl
253nm irradiation (aka UV-C) is considered the most destructive to virus and perhaps even bacterial DNA. Same peak wavelength as the large sterilizations carts used to do hospital rooms. It also happens to be the wavelength of EPROM ERASER lamps. I use my old EPROM eraser to sterilize everything (mostly groceries) that go into my 84 year old moms house. Also intended for the few masks that we have. We use sunglasses that significantly attenuate UV ~95%+. We also have no direct line of sight to the bulb and keep our hands either clear/shaded or gloved to avoid sunburn and messing with the DNA in our skin. A black matt surface is under the light to prevent reflection. The light is quite powerful because you can smell the ozone. Since I am stranded away form home without my light meter and other optiker gear and there is no manual online for this a 30 year old device , I estimated the irradiance from what EPROM’s require and the time we used to put on timer to erase them. Worked out to 7 seconds for viruses. Depending on the unit you have, you may have to remove the tray and possibly even defeat an interlock.
BE ULTRA CAREFUL NOT TO IRRADIATE YOUR SKIN OR GET THE LIGHT IN YOUR EYES. EVEN IF WEARING PROTECTIVE GLASSES, ENSURE YOU ARE PROTECTED FROM OFF AXIS LIGHT AND SPECULAR REFLECTIONS. THE LIGHT WAVELENGTH IS OPTIMAL FOR KILLING VIRUSES, BACTERIA AND IT DOES IT BY MESSING UP THE DNA. IT WILL DO THAT TO YOUR SKIN AS WELL.
A good solution might be establishing disinfection protocols using catering equipment.
Apologies for the copy-pasted email - takeway: Steam for 10 minutes or 70C bake for 30 minutes both show efficacy in killing e.coli (proxy for 'Rona), catering equipment is natively capable of those things, catering is not being done right now in many US cities, perhaps idle equipment becomes disinfection tool?
High impact, a day of reprogramming and protocol development becomes weeks of mask reuse.
Cold plasma, but there isn’t a lot of material available for it.
A real solution, but not something you can just play with. Bath the equipment in concentrated hydrogen peroxide vapor (do not try this at home!).
Dr. Lee, I know this is a bit behind your schedule, but check out these links, which some you may have seen.
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