# UV sanitizes????????



## Mags (Nov 17, 2005)

went to the barber a few days ago, and she had some sort of microwave thing that said barber sanitizer or something with a bunch of her scissors in it. The thing said caution, ultraviolet rays blah blah u know the average UV light stuff. How is this posible though? UV to me is harmful to eyes and skin, helps detect scorpions and stuff on credit cards, and is good for glow powder.


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## beezaur (Nov 17, 2005)

UV light "deactivates" most microorganisms. The efficacy depends upon the dose, meaning intensity and time. Different wavelengths have different "strengths."

In my work, I have prescribed UV disinfection for drinking water. It is also used in air circulation systems and wastewater.

Basically you get sick not from the bugs you catch, but when those bugs reproduce in vast numbers. UV radiation affects their ability to reproduce, usually does not kill them outright. Since they cannot reproduce in great numbers, i.e., they are inactivated, you don't get sick.

Scott

PS: the actual mechanism of inactivation is poorly understood and often debated. The most generally accepted idea is that the bugs' DNA is torn up by the radiation, making the bugs sterile. They simply live out their (very short) lives and die, leaving no future generations to carry on. Kinda sad, really.


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## Cypher (Nov 17, 2005)

I am currently in dental school and taking a microbiology course. It is true that UV can sterilize. UV light from 220-300 nm can cause thymine dimers in the DNA of the bacteria. It is a mutation that can keep the organism from multiplying or it will introduce a fatal mutation when it goes to transcribe the gene. I want to be a dentist, not a microbiologist, so there is probably much more to what I have said but that is what I understand about it. 

Daegan


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## UVvis (Nov 17, 2005)

The dimerized DNA and RNA also prevent expression of proteins and peptides. You are basically preventing the cells from being able to do anything.


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## Polar_Hops (Nov 17, 2005)

Strong UV can also ionize water, changing it's charge. It can accept another oxygen atom, becoming h202, or hydrogen peroxide.

I doubt the uv light at the barber shop had enough power, or a short enough wavelength lead to the formation of much hydrogen peroxide.


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## GadgetTravel (Nov 17, 2005)

Right, the UV radiation causes one of the four bases that are the building blocks of the genome of virtually any organism for link together (irreversibly) into what is called a Thymine dimer as described above. The Thymidine is one of the four bases that comprise the genome. UV is a type of radiation, as is visible or radio wave but in the case of UV it cant penetrate very large distances (as opposed to say x-rays which can penetrate). Since much of our body is covered with essentially a layer of dead skin, we are a little bit protected against UV. But if we get a lot, from the sun or an artificial source, it can be a problem.

In the cabinets that are used for a lot of work in such as growing bacteria or human cells in liquid culture (often tumor cells) they are made with all smooth surfaces, typically stainless steel. Usually they are have an airflow at the opening to keep stuff from getting in and out. If they are being used for real nasties they are completely sealed and you reach inside them in a sealed glove attached to the wall. The first kind, called a laminar flow hood is much more common. In either case, they are usually (virtually always) set up with a very powerful shortwave UV source in the light fixture as well as the visible source. While common practive is to disinfect with chemicals before and after use, the UV source is usually on a timer and goes on for a few hour in the middle of the night to blast anything that the chemicals didnt get. Since the bacteria or viruse dont have a coating like skin they are pretty sensitive.

I think UV at high enough intensity also causes other damage to cells. When you get a sunburn, that is essentially a burn caused by UV light. The DNA damage, the thymine dimers, is probably related to the way that UV damage can cause skin cancer. The lights in the cabinets I described above are pretty powerful and the cabinets should have big warning signs about the time that they switch on so that lab workers dont accidently get zapped.


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## senecaripple (Nov 18, 2005)

well, guess those cheap keychain uv wont sanitize much. i was going to momentarily flash it on my toothbrush and coffee mugs!


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## Cornkid (Nov 18, 2005)

LOL... 
No.. that wouldn't help very much.

-tom


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## Jumpmaster (Nov 18, 2005)

beezaur said:


> In my work, I have prescribed UV disinfection for drinking water. It is also used in air circulation systems and wastewater.



I wonder if that's what the things on the wall in the military dining facilities I've been in were for...they had what appeared to be BRIGHT UV light shining onto the wall above them.

JM-99


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## edakoppo (Nov 18, 2005)

What commercially available UV light would be the minimum for this purpose, or would it have to be homebrewed?


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## Wim Hertog (Nov 18, 2005)

edakoppo said:


> What commercially available UV light would be the minimum for this purpose, or would it have to be homebrewed?



Any UV light below 300 nm (UV-C) can be used. Most widely spread are germicidal fluorescent tubes. These are pure quartz tubes without phosphor coating. Peak wavelength is 253,7nm (mercury ).


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## gregw (Nov 18, 2005)

Take a look at the Aquastar for a portable UV Water Purifier..


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## PhotonWrangler (Nov 18, 2005)

Jumpmaster said:


> I wonder if that's what the things on the wall in the military dining facilities I've been in were for...they had what appeared to be BRIGHT UV light shining onto the wall above them.
> 
> JM-99



I think you're referring to a bug-catcher UV tube. There's a commercial product that sees a lot of use in grocery store deli counters and other food areas that uses longwave BL-style bulbs (longwave UV phosphor but no dark blue filter glass) and some sort of insect trap inside.


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## GadgetTravel (Nov 18, 2005)

Im sure there is a large supply of commercial products. Hospitals and labs are not using homemade lamps in their bio-hoods and for other similar applications.


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## Lightmeup (Nov 19, 2005)

Does anyone know what frequency range can cause damage to the human eye if exposed long enough or to a strong enough UV light? What about those "black light" bulbs that people use for visual effects at parties, etc., can they cause eye damage?


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## The_LED_Museum (Nov 19, 2005)

UV radiation with wavelengths below approximately 350nm would not be too good for the eyes and skin with prolonged exposure; a wavelength of 253.7nm is used by the UV Aquastar water purifier bottle (links to an evaluation of it on my website). This is within the wavelength range of UVC (ultraviolet C), and is *VERY BAD* for skin and eyes - the plastic of the bottle filters out the harmful UVC radiation though, so there is no danger whatsoever of unwanted exposure when the product is used as intended.


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## Cagmag (Nov 19, 2005)

My company distributes air purification products from RGF. They are industry leaders in the business of purifying air, food & water. Take a look at there website.....it has a ton of good information.

www.rgf.com


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## GadgetTravel (Nov 19, 2005)

In addition to disinfecting we use light tables which have UV lights in them for some work. They usually have 260nm and 320nm (I think). We have to wear at least goggles with both and almost exclusively are wearing full face shields. Wearing gloves for other reasons but they also protect against the UV. Years ago, occassionally someone would work with the UV tables with only goggles and the 260nm light on for too long (probably under 10 minutes but more than 2 or 3 minutes). The look was like someone who had spent too much time in the sun at the ski slope wearing googles and no sunscreen.


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## edakoppo (Nov 21, 2005)

Wim Hertog said:


> Any UV light below 300 nm (UV-C) can be used. Most widely spread are germicidal fluorescent tubes. These are pure quartz tubes without phosphor coating. Peak wavelength is 253,7nm (mercury ).



Thanks, but I'm afraid my original question was imprecise. Are there any commercially available flashlights that operate in this range, or must they be homebrewed? Hell, are flashlights even anywhere near powerful enough for the purpose?


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## Wim Hertog (Nov 21, 2005)

edakoppo said:


> Thanks, but I'm afraid my original question was imprecise. Are there any commercially available flashlights that operate in this range, or must they be homebrewed? Hell, are flashlights even anywhere near powerful enough for the purpose?




The only "flashlights" I can think of are those 4 or 6W fluorescent lanterns with germicidal tubes. 

http://cgi.ebay.com/SHORTWAVE-UV-Ul...oryZ3223QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Forget about LED's below 350 nm, maybe a very expensive UV HID flashlight might do the trick...


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## Zelandeth (Nov 21, 2005)

Simple answer: No.

As far as I know, there are no LED's which emit in the UV-C range at present (though I could be wrong).

If you must have a portable germicidal lamp, a cheap F4T5 fluorescent lantern can be turned into one simply by replacing the F4T5 with aG4T5 tube, and removing the plastic lens.

Bear in mind though THE OUTPUT OF THESE TUBES IS INTENDED TO BE HARMFUL TO LIVING TISSUES, EYES AND SKIN INCLUDED! These thing ain't toys, and are dangerous. So make sure you know what you're doing with them.

I collect lamps here, and have a couple of germicidal tubes somewhere. I've never powered them up, and until I've put together something specifically for them, I will not be doing so. UV-C is nasty, nasty stuff.


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## PhotonWrangler (Nov 21, 2005)

edakoppo said:


> Thanks, but I'm afraid my original question was imprecise. Are there any commercially available flashlights that operate in this range, or must they be homebrewed? Hell, are flashlights even anywhere near powerful enough for the purpose?


 
There are portable commercial UVC fluorescent lamps. Some are used for mineral identification. I have a couple of UVC "mineralights" that I use for this purpose. Craig has a review of one of them on his website.

EPROM erasers also use small fluorescent germicidal tubes, so your EPROMS can be erased and disinfected at the same time!


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## edakoppo (Nov 22, 2005)

Thanks to all for replies. Not viable for the applications I had in mind.


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## Lightmeup (Nov 24, 2005)

PhotonWrangler said:


> EPROM erasers also use small fluorescent germicidal tubes, so your EPROMS can be erased and disinfected at the same time!


You're kidding, right? (About the disinfecting).


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## Zelandeth (Nov 24, 2005)

Nope, not kidding. It's the same type of lamps which are used for both purposes.

It's exactly the same shortwave UV which zaps nasties there as what causes the reaction in die of you EPROM causing it to be wiped.


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