COVID-19 Emergency - Using UV Lamps to sanitize Face Masks overnight

[Caliaxy]

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. 

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).

[1sciguy]

Every town has a dry cleaner.  They use Tetrachloroethylene, which evaporates completely.  Millions of women would complain if there was a residue on their intimate apparel.  I would suspect that no virus or bacteria could live through such a bath.  I can't say whether or not it would harm any other aspect of the material composition.

[KaneTW]

Ultraviolet Germicidal Irradiation Handbook by Kowalski and The Ultraviolet Disinfection Handbook by Bolton and Cotton are what I use as references. Primary sources are listed in the books.

[KaneTW]

If there are any references for UV mercury germicidal lamp efficiency, please send them may way.  The study I was referring to is

Hao & Han, Qiuyi & Zhang, Shanduan. (2013). “254 nm Radiant Efficiency of High Output Low Pressure Mercury Discharge Lamps with Neon-Argon Buffer Gas” Applied Mechanics and Materials. 325-326. 409-412. 10.4028/www.scientific.net/AMM.325-326.409.

That is where I obtained by 30% estimate from.

from Kowalski's book above

[pipe2null]

@KaneTW: Do you mind if I repost the UVGI info in another thread?  Most people don't care, but I've been attempting to collect reference info into one place/thread.  I've seen too many posts where people pull numbers out of their backsides that don't line up with the reference info I've found so far.

Since there are a bunch of people working on other angles/problems, I've been trying to figure out the UVC intensity and exposure time requirements to kill COVID-19 or at least SARS-CoV.  I'm hoping that mathematically it's possible to stick a UVC light in a can, pipe air through it, and kill viruses fast enough to meet or exceed the peak airflow from breathing...  With the info I have so far, it seems like it's possible, but I don't have enough tangible data yet.

[KaneTW]

@KaneTW: Do you mind if I repost the UVGI info in another thread?  Most people don't care, but I've been attempting to collect reference info into one place/thread.  I've seen too many posts where people pull numbers out of their backsides that don't line up with the reference info I've found so far.

Since there are a bunch of people working on other angles/problems, I've been trying to figure out the UVC intensity and exposure time requirements to kill COVID-19 or at least SARS-CoV.  I'm hoping that mathematically it's possible to stick a UVC light in a can, pipe air through it, and kill viruses fast enough to meet or exceed the peak airflow from breathing...  With the info I have so far, it seems like it's possible, but I don't have enough tangible data yet.

Go ahead. The books I mentioned are used to design UV systems for air (e.g. in a HVAC system) and water disinfection. There's also (commercial, with free trial) http://www.uvcalc.com/ which can be used to model reactors so that you get the required target dose.

The required dose rate depends on whether you want to kill everything immediately or whether the system is circulating and a partial kill is fine. It also depends on whether there's a constant influx of new pathogens or not.

There was a paper on the relevant disinfection kinetics but I can't find it again. I'll let you know if I find something.

[helius]

Interesting details about UVC lamps in air handlers. What about the ozone generated? Is it a safe level or is there some way of filtering it out?
Would the UVC be more effective on the intake side (before the air filter, so microbes would be killed and then filtered), or on the output side where it could help to sterilize the evaporator coil?

I have bought a 15 W UV-C lamp armature.

There are also hand-held, battery-powered UVC wands that can be used to sterilize surfaces and objects (like mail or door handles).

[pipe2null]

If you were going to choose one book over the other, which one would you go with?  I'm hoping you'll say "Ultraviolet Disinfection Handbook" cause that will get delivered much faster... 

The idea I'm working from is an in-line UVC virus killer to sterilize exhaled air from covid positive people who are using CPAP/BiPAP/whatever.  And if you happen to have a metal housing available, you could use same principle to sterilize inhaled air for a healthy person.  You should probably be able to use plastic/PVC housing for exhaled air for a somewhat short term basis, but not inhaled air due to photo degradation of plastic, ie undiluted unhealthy fumes.  So, target is "quick" kill with no recirculation.  Due to variety of available UVC sources (or un-availability as it may be for some people), I'm attempting to create a reference design that is easily modifiable based on your available UVC source, or prove that the source is inadequate.  That's the idea anyway.  I have 3.5W, 60W, and 100W UVC bulbs of different geometries ordered and I'll have 2 of them within the week. 

Whether or not my idea works out, the most important thing is getting the right information so people don't hack something together out of desperation, think it's working, but the bulb is grossly inadequate, for instance.

[Stray Electron]

Interesting details about UVC lamps in air handlers. What about the ozone generated? Is it a safe level or is there some way of filtering it out?
Would the UVC be more effective on the intake side (before the air filter, so microbes would be killed and then filtered), or on the output side where it could help to sterilize the evaporator coil?

   I already covered the first part of this. You can buy 254nm lamps that have a doped envelope that blocks the 185nm radiation so they don't produce ozone.

   Regarding the 2nd part, IMO the UVC source would be most effective on the dirty side of the filter since the virus should be trapped on that side of the filter.  That means that to protect someone from the virus it needs to be on the intake side but for preventing an infected person from spreading the virus that it needs to be on the human side of the filter.  However having the UVC on the human side of the filter could also expose the skin and eyes to harmful UVC radiation so the design would have to prevent that.  Also if the mask is designed only to prevent spreading the virus and to only filter exhaled air and not inhaled air then ozone generation shouldn't be an issue and may actually be a benefit since it would help kill the virus.  So it looks like you would need two different mask designs to best serve two different purposes.

[KaneTW]

Interesting details about UVC lamps in air handlers. What about the ozone generated? Is it a safe level or is there some way of filtering it out?
Would the UVC be more effective on the intake side (before the air filter, so microbes would be killed and then filtered), or on the output side where it could help to sterilize the evaporator coil?

Doped UVC tubes generate negligible amounts of ozone-generating UV as far as I know (haven't concerned myself with air disinfection too much, only water).

No idea about intake/outtake. Industry practice for HVAC seems to be to install them in the return duct, but more research is needed.

If you were going to choose one book over the other, which one would you go with?  I'm hoping you'll say "Ultraviolet Disinfection Handbook" cause that will get delivered much faster... 

It's been a while since I used this for my own research, but Ultraviolet Germicidal Irradiation Handbook appears to be more general whereas Ultraviolet Disinfection Handbook focuses more on water disinfection. You can try both out via libgen and see which one is more pertinent to your questions.

[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.

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).

[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]

The University of Nebraska protocol UV disinfection exposes only the front of the mask.

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]

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.

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.

[KeepItSimpleStupid]

The photo shows 2 levels of lines to hold the masks.  That appears to be missing in the words.
there is also a 7 fold safety margin.  Based on the location of the sensor, it looks like more than.

So, should I make one at home from a cardboard box lined aluminum foil and an HVAC UV-C bulb? 
They only get 3-5x, but they wear the mask the entire shift.  I have a few N95, non health care masks  3M 8211 at home and a half-face non disposeable respirator.

[UnaAllan]

I guess you can desinfect masks  with the sanitizer or just wash it in the machine with high temperature

[KaneTW]

No. You cannot. That ruins the mask's protective properties (for a N95-type mask)

[Zero999]

Since this is an electronic forum - what about RF at a resonant frequency which destroys the virus?

I found this article where about 60GHz was effective for their sample, but its a bit old.
https://www.livescience.com/7472-kill-viruses-shake-death.html

That's not RF but light, modulated at 60GHz. Microwaves are absorbed too easilly by water to be effective. No details are given, but it's a much higher frequency (near infrared to visible) modulated with 60GHz. Anyway, it sounds like something which works in the lab but is of no practical use, at this stage.

[Zero999]

I can recommend this bag. A very useful thing.
https://uv-sanitizerr.com/product/uv-c-sanitizer-bag/
I use this myself. 

It looks like a fake to me. Test it by putting a banana quite close to the LEDs. If it turns brown, then they're genuine UVC LEDs, otherwise it's fake.

Sadly, most LED sterilisers are fake. That looks like a dodgy site. There are no safety warnings about any of there products, because they're all fake. Real UVC sterilisers emit dangerous radiation which can burn the skin and eyes. Fake UV sterilisers, emit UVA, visible violet, or blue light, which is safe, but useless for disinfection. Return it and demand a refund.

[KaneTW]

UVC LEDs are like 2% efficient, and that bag claims to use 10W (5V/2A). .2W of UVC is way too little to get germicidal action on a surface in a reasonable time frame. Batteries will die before it does anything.

[Zero999]

UVC LEDs are like 2% efficient, and that bag claims to use 10W (5V/2A). .2W of UVC is way too little to get germicidal action on a surface in a reasonable time frame. Batteries will die before it does anything.

Of course it's a scam. The website says they're an American company, but I doubt it.
https://uv-sanitizerr.com/have-a-question/

Perhaps a prominent YouTuber such as Dave or Big Clive, should do a video on this.

[Simon]

scammer banned

[NiHaoMike]

I wonder why they don't salvage flyback transformers from discarded CRT TVs (should be fairly easy to find a lot that still work due to the sheer number) and just use an arc as the UV source. It would also generate ozone, so it would even be dual action sanitation.

That said, I'm getting the impression masks are a lot easier to get now and just having a bunch of them to rotate through would probably be the easiest solution.

[Simon]

You just wash the masks and have a few.