Electronics > Projects, Designs, and Technical Stuff
COVID-19 Emergency - Using UV Lamps to sanitize Face Masks overnight
Zero999:
--- Quote from: profdc9 on March 26, 2020, 01:10:50 pm ---Alcohol unfortunately can not be used to disinfect masks. It destroys a charged layer in the N95 masks that attracts virus particles. I wrote up a proposal for building a UV sterilizer for mask a couple days ago. Anyone who is interested please E-mail me:
https://drive.google.com/open?id=1wF4yYgSE1n0Jqewb8JdwosTRhx0X89wF
This is a Google Drive link.
It is a difficult problem because UV can also potentially destroy the elastomers in the mask so that the mask no longer fits well on the wearer. There is also cumulative damage to the filtration capability. But it presently seems the most promising approach. A paper in 2015 studied this:
W.G. Lindsley, S. B. Martin Jr., R. E. Thewlis, K. Sarkisian, J. O. Nwoko, K. R. Mead, and J. D. Noti, “Effects of Ultraviolet Germicidal Irradiation (UVGI) on N95 Respirator Filtration Performance and Structural Integrity,” Journal of Occupational and Environmental Hygiene, v 12., pp. 509-517 (2015).
https://www.researchgate.net/publication/274090116_Effects_of_Ultraviolet_Germicidal_Irradiation_UVGI_on_N95_Respirator_Filtration_Performance_and_Structural_Integrity
There's a crowdsourced actively maintained document of resources at http://ppereuse.com/ .
Best,
Dan
--- End quote ---
The lamp mentioned in your proposal produces ozone, which is good because it will not just sanitise the surface, but penetrate more deeply. The downside is ozone can be more damaging to fabrics and elastomers.
https://www.amazon.com/AGAWA-Ultraviolet-Disinfection-Sterilization-Germicidal/dp/B085CGGQFR/
I wonder how good the cheap LED germicidal lamps are? The blurb for the one linked below says it doesn't produce any ozone, so no good for masks, as it'll only sterilise the surface. It's inexpensive, considering the price of discrete UVC LEDs from reputable distributors. I accept distributors have lots of overheads, but I'm cynical of really cheap things.
https://www.amazon.com/dp/B085VWPT9C/ref=psdc_2314207011_t1_B085CGGQFR
NiHaoMike:
--- Quote from: jfiresto on March 26, 2020, 12:34:24 pm ---Doctors scramble for best practices on reusing medical masks during shortage: "Referring to a paper published in the journal Annals of Occupational Hygiene in 2009, among others, the researchers compared and contrasted ... different methods for sterilizing N95 masks, many of which were ineffective."
Two were, however: "70 C / 158 F heating in a kitchen-type of oven for 30 min, or hot water vapor from boiling water for 10 min...."
--- End quote ---
Wouldn't a kitchen oven, which is designed for much higher temperatures, overshoot badly? (That's a common problem seen when trying to use a kitchen oven for drying 3D printing filament.) I suppose if you get a "dumb" oven designed for 240V and run it on 120V it would work a lot better.
Perhaps the simplest solution is to just put them in a box and just leave them for the 9 days or so (which is turning out to be quite conservative) it takes for the virus to degrade on its own. It would also be interesting to see how long it takes to destroy the virus at lower temperatures like 120F. (The 9 day figure was under near ideal conditions, at room temperature it's more like 3 days.)
james_s:
Some kitchen ovens are better than others at regulating low temperatures. If you were willing to modify the oven you could install a PID controller to precisely control the temperature at any level you want.
Mechatrommer:
--- Quote from: NiHaoMike on March 26, 2020, 01:52:03 pm ---overshoot badly?
--- End quote ---
the simple trick is to undershoot the thermostat setting by a bit. but i dont think covid will be happy with this overshoot behaviour.
Zero999:
--- Quote from: Mechatrommer on March 27, 2020, 05:36:58 am ---
--- Quote from: NiHaoMike on March 26, 2020, 01:52:03 pm ---overshoot badly?
--- End quote ---
the simple trick is to undershoot the thermostat setting by a bit. but i dont think covid will be happy with this overshoot behaviour.
--- End quote ---
If a kitchen oven does overshoot, I've never had a problem with it. I frequently use my oven on the 60oC setting to dry my shoes with no problems. I'd hope a decent oven will be able to leaven bread, on its lowest setting, without killing the yeast.
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