Electronics > Projects, Designs, and Technical Stuff
COVID-19 Emergency - Using UV Lamps to sanitize Face Masks overnight
Zero999:
--- Quote from: Stray Electron on March 28, 2020, 01:30:14 am ---
--- Quote from: Zero999 on March 26, 2020, 01:33:56 pm ---
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
--- End quote ---
FYI. Germicidal lamps emit 254nm UVC radiation. Usually they are mercury lamps and mercury emits both 254nm and 185nm radiation. the 185nm radiation is what generates ozone and the 254nm is what directly kills viruses. However some germicidal lamps use a doped envelope (aka bulb) that block 185nm so those lamps do not generate ozone. A moral of the story is that if you want ozone then make sure that you use a lamp that doesn't have a doped envelope. Depending on the doping agent, the envelope on a doped lamp may have a greenish cast to it if you look at it in daylight.
--- End quote ---
Yes, that's true, germicidal lamps are made the same as ordinary fluorescent tubes, but with quartz and no phosphor, so the UV passes through.
I was talking about newer UVC LED-based germicidal lamps. The ones I linked to looked very cheap. I also question their efficiency. The data sheets for UVC LEDs I've found have an efficiency of around 2%, which is miserable compared to the 30% offered by traditional mercury lamps.
http://www.farnell.com/datasheets/2774752.pdf
https://www.ushio.com/files/specifications/germicidal-low-pressure-mercury-arc.pdf
jeremy:
FYI in that video he is using alcohol to clean surgical masks, not N95 respirators. The respirators are what is damaged by the alcohol.
jfiresto:
Another sterilization method: using vaporized H2O2 to sterilize N95 masks
Stray Electron:
--- Quote from: Zero999 on March 28, 2020, 10:24:06 am ---
--- Quote from: Stray Electron on March 28, 2020, 01:30:14 am ---
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
--- End quote ---
Yes, that's true, germicidal lamps are made the same as ordinary fluorescent tubes, but with quartz and no phosphor, so the UV passes through.
--- End quote ---
I understand but my point is that some 254nm lamps use doped envelopes so they won't pass 185nm and are incapable of creating ozone. If you want ozone then you must use lamps that have undoped quartz envelopes.
The plain glass lamps with phosphor are 366nm lamps that are used for generating black light for cosmetic effects. They're useless for killing bacteria or virus and also don't create ozone. They have a SLIGHT effect on bacteria and virus but their killing power is literally about 0.0001% of what a 254uM lamps is. I think they cover that in here https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3831650/
Stray Electron:
If you really want to play with a kickass UVC source then go find one of the old Mercury vapor street lamps. We played with them when I was a kid and the ones that we used were 400 Watt lamps and had a small mercury vapor lamp with an undoped quartz envelope inside of a larger plain glass envelope that contained phosphors. We broke open the outer envelope and removed it and just ran the inner lamps by itself. They emitted tons of 254um radiation and any florescent material without about 20 feet would glow BRIGHTLY. They would also give us sun burns if we run one for more than about an hour and they also generated a lot of ozone.
FYI They have a negative resistance so they are supposed to be used with a ballast.
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