Im going to buy 36 watt omron brand UVC lamb.I need to learn the optimal distance and time that I have to put the masks on it to reach 60 mJ / cm2 energy with this lamp. 36w uvc bulb means 36 uses it but i don't know the energy it emits. So i need optimal distance and time. I need to reach 60 mJ / cm2 of energy
I will recommend to go for a tried and tested method. These are crucial times and we can not afford experiments. Not with respect to Covid-19.
We must do this kind of things when there is no other method. when there aren't masks, what wıll we do. we have to thınk every methods
Efe Kırtıllı . Bless you for your creativity and forethought. I like your idea. The next level refinement might be to address the interior of the "fabric" which might not be exposed to the UV. Microwave? . . If a cotton mask is better than nothing . . .
Efe Kırtıllı Call the manufacturer. Explain your need, and ask the efficiency in getting UV power. I worry a bit that you may need more power to make this a reasonable idea. However, you are offering the manufacturer an important idea. I believe for this reason that you may ask for, and expect the attention of a tech, rather than a sales person. You may bless far more than your stewardship with this idea and encouragement. BULLY FOR YOU!
UV lamps are typically like a fluorescent tube (Ionizing mercury), except without the fluorescent coating. You may actually get more efficiency than regular fluorescent lamps.
In the meanwhile, let's start with fundamental principles. I agree that intensity is what you are interested in.
The intensity from small, point-like or spherical sources drops off according to 1/(distance squared). For long cylindrical sources, it drops off according to 1/(distance). Reflectors can nearly double the intensity by gathering what would be lost out the back.
One problem with N95 masks is that I hear that they may not fail first from contamination, but by plugging up. With that in mind, a cotton cover may make a lot of sense. I am not sure if they plug up more from the inside or the outside.
This plugging up failure is consistent with my experience crawling around in my attic with cellulose insulation. Very quickly I start to have difficulties getting air through the darn things.
How is that for "I have no idea?"
I think it is dangerous as the benefit gained is far lesser than the risk involved.
Efe Kırtıllı
From Covid-19 Pandemic: Face Mask Disinfection & Sterilization for Viruses
https://consteril.com/covid-19-pandemic-disinfection-and-sterilization-of-face-masks-for-viruses/
UVGI:
A UV-C lamp (80W, 254 nm) is used to expose the contaminated FFRs to UV radiation (≥1 J/cm2 total dosage) for 15 minutes on each side of the mask (outer and inner). Use of this method resulted in an average log reduction of 4.81 of viable virus. Both dosage and wavelength of UV light are critical for inactivation, and when designing a procedure users must bear in mind that UV light is based on line-of-sight, and any part of the mask in shadow will not be disinfected. Further, it is vital to ensure that UV-C dosage is measured at the mask as dosage can be significantly reduced with increased distance from the source(s). One potential problem with implementing UVGI disinfection is penetration to the inner layers of some mask designs, which may not be exposed to the same dosage. Certain strap designs prone to twisting may also inhibit UVGI disinfection and a secondary disinfection step only applied to the straps of the mask may be necessary to counteract this.
While testing has shown that exposure to UVGI does not reduce the aerosol penetration to above 5%, statistically significant increases in penetration do occur meaning that repeated use of this method of disinfection will degrade masks over time (7). However, anecdotal evidence from facilities like the University of Nebraska where mask reuse has been fully implemented using UVGI light disinfection protocols suggests that the repeated usage of the mask leads to degradation far faster than the disinfection protocol does. At that facility the average number of times masks have been able to be reused is 3 times before fit testing failures are observed, whereas masks were run through the UVGI disinfection protocol 50 times before significant degradation of seal integrity was observed (13).
Efe Kırtıllı They also suggest using 65C for mask disinfection in oven (in the article). I have heard/see this strategy somewhere else too.
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