Electronics > Projects, Designs, and Technical Stuff
COVID-19 Emergency - Using UV Lamps to sanitize Face Masks overnight
helius:
Sorry if I wasn't clear, I used "air handler" as typical jargon for main HVAC appliance. The integration of UVC into a mask is interesting but probably too complex for me to consider.
profdc9:
The University of Nebraska protocol UV disinfection exposes only the front of the mask. There are some supporting studies to show that UV germicidal radiation is effective at disinfecting SARS and influenza. Because the elastomer band is held in by staples, removing the elastomer band would probably compromise the mask as it would tear it. Better just to tuck the elastomer band behind the mask when exposing it. Furthermore, the damage threshold to the band is typically about 5 to 10 times that of the mask layers.
--- Quote from: Caliaxy on April 01, 2020, 05:46:35 pm ---
Nice! Not sure how effective this is (what's the penetration of uv light through the mask's material?), but I have two suggestions:
1. In your photo, the lamp is in the middle of the box and the mask on the left side, next to the wall. This way, the "dark side" of the mask (that sits in its own shadow) doesn't seem to get much reflected light. I suggest putting the light source by the wall and the mask in the middle of the box, maybe suspended from the lid.
2. Remove the elastomers before the uv treatment, sterilize them with alcohol and attach them after the uv cycle. Thus, they won't degrade because of the uv light (they might, because of the alcohol but, hopefully, at a lower rate).
--- End quote ---
KaneTW:
There's a system using vapor phase H2O2 for disinfection that appears to not degrade the filter media (https://www.fda.gov/media/136386/download).
Caliaxy:
--- Quote from: profdc9 on April 02, 2020, 02:24:43 pm ---The University of Nebraska protocol UV disinfection exposes only the front of the mask.
--- End quote ---
Well, not according to their currently published procedure:
https://www.nebraskamed.com/sites/default/files/documents/covid-19/n-95-decon-process.pdf
Or, at least, they don't mention it explicitly. However, they do show a diagram (page 4) and photos (pages 1, 12 and 15) of the sterilization room with two uv light sources (which they call "torches"), one on each side of the masks hanged on lines in between the torches. It makes sense to me, as the mask can be contaminated on both sides while manipulated (removed) and you would also increase the penetration of uv light if both sides are exposed. They do tuck the elastic bands on the inside of the mask, though.
profdc9:
--- Quote from: Caliaxy on April 02, 2020, 06:58:43 pm ---Or, at least, they don't mention it explicitly. However, they do show a diagram (page 4) and photos (pages 1, 12 and 15) of the sterilization room with two uv light sources (which they call "torches"), one on each side of the masks hanged on lines in between the torches. It makes sense to me, as the mask can be contaminated on both sides while manipulated (removed) and you would also increase the penetration of uv light if both sides are exposed. They do tuck the elastic bands on the inside of the mask, though.
--- End quote ---
I looked at their other presentation and didn't see both of those sources. So they are using two, I stand corrected. With their method, however, there is a wide variation in distance from the sources and so I think that would provide a lower dose to the masks on the edge of the row of masks. It would be better if they turned their torch towers horizontal to get more even illumination. If I interpret their diagram on page 4, the detector for the dose is at the wall. However, figure 11 does not appear to be consistent with page 4. Page 4 shows the masks on the left side and the two sources on one side of the masks, while figure 11 shows the masks between the two sources.
You could place two sources in the box I suppose and the mask between them, or hang the mask from the top of the box and let the walls of the box reflect the UV and illuminate both sides.
By placing the source in the middle and the masks on the edge, the dose can be evened out somewhat, especially if there are reflective walls so that more of the illumination can be diffused more evenly but then the mask must be flipped over to expose both sides. I think it is better to try to keep the dose even because the cumulative damage to the mask depends on the dose, and so if the dose is greater than required, the number of reuses is limited.
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