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

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KaneTW:

--- Quote from: pipe2null on April 01, 2020, 11:07:49 pm ---@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.

--- End quote ---

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?


--- Quote from: taydin ---I have bought a 15 W UV-C lamp armature.
--- End quote ---
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:

--- Quote from: helius on April 02, 2020, 12:00:54 am ---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?

--- End quote ---

   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:

--- Quote from: helius on April 02, 2020, 12:00:54 am ---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?


--- End quote ---

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.


--- Quote from: pipe2null on April 02, 2020, 12:19:11 am ---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...  ;)

--- End quote ---

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.

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