UV-C Light, does it affect/damage LED CoB chips with repeated exposure?

dvsDave

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So, I was looking at large UV-C lights designed to disinfect a room over an hour's time. Some of these lights have impressive output, and it got me thinking. If the UV-C light was placed on the stage, would the UV output effect LED emitters with repeated exposure? To clarify, non-IP65 rated fixtures that happen to be aimed at the part of the stage where the UV-C light fixture is placed. (I said non-IP65 fixtures because I'm wondering if outdoor fixtures already have UV filters in place, but I could be wrong about that)

Similarly, how would it affect various types of projectors? Would you need to have a dowser on a projector to protect it?

In essence, is UV-C going to damage common gear on stage with repeated exposure (1 hour a day, 5-6 days a week)?
 
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mbrown3039

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Great question...I hadn't even though of this. Let me ping some folks....m
 
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dvsDave

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mbrown3039

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I've pinged three audio, two video and one lighting manufacturer -- I'll update here as they reply.
 

mbrown3039

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The lighting manufacturer has already replied: they're looking into it, but the short answer is "yes" - the UV-C light will cause physical damage to the plastics used in construction. They're running tests to see to what degree but it will take a few weeks (at least) before they have any conclusions.
 

macsound

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This brings up another thought, how do you measure the "brightness" of the UVC light at the areas you're most needing it? That is, making sure theres not shadows on the seating and doors and that the light isn't too far away and "dim" to be effective.
Both because you're not supposed to be personally exposed to the light, but also because the light that's doing the killing isn't part of the visible spectrum.
 

dvsDave

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This brings up another thought, how do you measure the "brightness" of the UVC light at the areas you're most needing it? That is, making sure theres not shadows on the seating and doors and that the light isn't too far away and "dim" to be effective.
Both because you're not supposed to be personally exposed to the light, but also because the light that's doing the killing isn't part of the visible spectrum.
I can answer that one, there are UV test-strips you can get to measure accumulated UV exposure.
 

jtweigandt

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For the most part, IMHO, the strategy of using direct UVC to disinfect a room is probably a waste of UVC. What we know now, that we didn't know a few months ago is that fomite transfer (getting covid from a surface or thing)
is probably a very small occurance compared to airborne.. either droplet or true aerosol... The spectrum from droplet to aerosol is a true continuum and the distinction between the two is largely one used for
definition in studies. Bottom line.. you get this stuff from breathing it for the most part.. probably droplets to the eye is a possibility as well.. Your tears drain to your nose via the tear ducts.. thats why your nose runs when you cry.

I am using UVC in my office... but I bought troffer units that have the UVC sealed in a highly reflective chamber and circulate the air in the room past it. Not cheap.. but no damage to people or stuff.. and probably a more targeted use of the UVC
They also make UVC units that can be installed easily in ducts or cold air returns of a furnace.

So my UVC is working on the air 24/7 even while people are present. Vs overnight... once a day. I do run an ozone unit on a timer every night though..Ozone isn't particularly "stuff friendly" either. Make sure the Parakeet is in the other part of the building.

We set the intakes to take in maximal outdoor air, and have left the fans of the HVAC running continuously since Mid March... more expensive, but dilution is your friend here. Exposure seems to be somewhat dose/time dependant..
 

mbrown3039

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...I do run an ozone unit on a timer every night though..Ozone isn't particularly "stuff friendly" either. Make sure the Parakeet is in the other part of the building.
Hmmm, ozone....hadn't thought about that. Decades ago (literally) I ran a chain of car detailing shops and ozone was the hot ticket for getting rid of persistent odors (think spilled milk that got into the carpet padding during a balmy Chicago summer).

How big is your ozone machine? Whole office-sized or room-sized?
 
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macsound

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For the most part, IMHO, the strategy of using direct UVC to disinfect a room is probably a waste of UVC. What we know now, that we didn't know a few months ago is that fomite transfer (getting covid from a surface or thing)
is probably a very small occurance compared to airborne.. either droplet or true aerosol... The spectrum from droplet to aerosol is a true continuum and the distinction between the two is largely one used for
definition in studies. Bottom line.. you get this stuff from breathing it for the most part.. probably droplets to the eye is a possibility as well.. Your tears drain to your nose via the tear ducts.. thats why your nose runs when you cry.

I am using UVC in my office... but I bought troffer units that have the UVC sealed in a highly reflective chamber and circulate the air in the room past it. Not cheap.. but no damage to people or stuff.. and probably a more targeted use of the UVC
They also make UVC units that can be installed easily in ducts or cold air returns of a furnace.

So my UVC is working on the air 24/7 even while people are present. Vs overnight... once a day. I do run an ozone unit on a timer every night though..Ozone isn't particularly "stuff friendly" either. Make sure the Parakeet is in the other part of the building.

We set the intakes to take in maximal outdoor air, and have left the fans of the HVAC running continuously since Mid March... more expensive, but dilution is your friend here. Exposure seems to be somewhat dose/time dependant..
I've read a bunch about the airborne aerosolized spit thing too and the part I can't wrap my head around is aiirflow with large vs small spaces. In an office building where the ceilings are 8-10' tall, airflow is higher I assume because the more complicated the space, the more supply and return vents. So more chance that sick people in the same general office space will have their own breathing sucked up with a relatively closeby return vent.

In a theatre there may only be one massive return because the air has naturally cycled via convection and conditioned air doesn't have the risk of being fed directly back in via the return.
So in that situation, is there fear that aerosolized spit potentially with viruses would be "blown" in a particular direction toward that return and affect everyone in between, vs if the system was just turned off, it would disperse on it's own and create a "natural" cloud based on physical location and not forced airflow.

TL;DR Is turnning a huge AC on kind of like putting everyone in a roller coaster with the sick person sitting at the front.
 

mbrown3039

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Ok, one of the audio manufacturers said that UV-C will shorten the life expectancy of the plastics they use by about 10% but would have no effect on the diodes. In summary:

Plastics: 2/6 say "Yes, UV-C will degrade"
LEDs: 1/6 says No, 1/6 says "yes, but unknown to what degree"
 
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jtweigandt

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In a large space.. or smalI I would rather have the air circulating.. 1. Because most air handling has at least some fresh air intake.. dilution.. 2. A “hot spot” becomes less hot via dilution. 3. Any filtration is better than none. Can move up in the MERV rating... but any filter that removes some of the dust/ droplets, and in the case of A/c condenses the moisture and drains it away.. is a good thing. For almost any pathogen we know of.. there’s a minimum exposure level maybe thousands of viral particles. In the case of COVID, we don’t know the number, but there’s some pretty good indicators that less viral load probably means less severity even if you get it.

Think of the exponential growth curve... it’s a race... your bodies defenses vs viral replication... 10 particles vs 100 vs 10000.. you can give yourself a day or 2 or 3 head start on an immune response..

My day job is Veterinarian. We have gotten really good at preventing, and containing “kennel cough” in boarding units. Air flow is king. I have been through a few times where we pretty much city wide had to ruin a bunch of folks vacation plans because everyone who boards had to have a brief time out to break the chain...

My ozone unit was originally purchased for ”spot” odor control in the front part of the office. Little cube, but turn it up to high, and in about 5 minutes 1000 sq feet of office smell like we have a motor with really bad brushes running. So when this hit, I just set it to high,put it on a timer, and it runs on full for about an hour each midnight. By morning, we don’t smell the residual.
 

Derickls

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There is a big push, especially by the IES, towards upper room air disinfection with UV-C. Basically studies have found that UV-C surface disinfection leaves a lot to be desired as dirt and dust can block the UV-C wavelengths. The UV-C light is actually aimed up towards the ceilings and is always on.


Here is a nice FAQ page the IES has put togehter:
 

jtweigandt

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This study done in hospital dealt with bacterial infections mostly, but did show that a very significant impact can be made with UVC air disinfection http://www.medillum.com/wp-content/uploads/2019/07/peer-review-ajic-cleaning-air.pdf

So kind of like mask wearing.. not perfect.. but major impact... Each piece of the chain we can put a roadblock into is a good thing.

I also ordered a couple free standing HEPA filter units that have a UVC chamber for a couple of smaller spaces off of amazon.
 

TimMc

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I am not a medical expert, I'm not a virologist, but I think the idea of wholesale UV-C disinfection of large cubic volume spaces in performance facilities is greatly over-rated, likely ineffective at doing what people *think* it does (at least in auditoriums and on stages), and is harmful to dyes, most plastics, etc. Ozone (which I use in my home) is a powerful oxidizer and is also harmful, over time, to rubber, plastics, some metals, dyes and fabrics.

If this is to be part of "sanitary theater" to make patrons, investors, micro-managing board members, etc feel good then you'll have little choice. UV-C treatment of recirculated air is probably the most beneficial use. /opinon
 

mbrown3039

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I've heard back from one of the video manufacturers. Update below:

Plastics: 2/6 say "Yes, UV-C will degrade," 1/6 says "no effect"
LEDs: 2/6 say No, 1/6 says "yes, but unknown to what degree"
 
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mbrown3039

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And now another audio manufacturer. Update below:

Plastics: 2/6 say "Yes, UV-C will degrade," 2/6 say "no effect"
LEDs: 3/6 say No, 1/6 says "yes, but unknown to what degree"
 

EdSavoie

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The short answer is to look at the physical construction of UV-C emitters. Their packages are vastly different from normal LEDs, generally being of a ceramic construction with a quartz lens in order to avoid the chip degrading itself. As bigclive points out, it's a very good way to spot a fake germicidal lamp from a real one!


But yeah, LEDs using plastic construction and plastic lenses would be particularly prone to damage. LED Fixtures using actual optics (Think an LED COB in a moving head) are probably fine if it has a non-quartz glass lens.

Plastic fixture bodies are a whole other can of worms though...
(all of the above of course depends on the exact plastics involved. i'd also be concerned about degradation of phosphor coatings on white LEDs)
 
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