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I'm interested in using some UV LEDs to light some projects. Specifically, painting some designs on RC aircraft with florescent paint and illuminating them with UV light for night time visibility. The LEDs I'm considering are 400-405nm, 5mm, 30mA.

Can this amount of UV light cause sunburn or eye damage? What safety considerations should I take into account?

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  • \$\begingroup\$ Upvote. I'd like to add to this question. Is there a way to tell if my UV LEDs are outputting to much UV? I have a large color kinetics fixture whose RGB LEDs were all replaced with UV LEDs (hundreds of them) and I have no way of knowing whether I should be using this in public or not. A datasheet isn't possible at this point and I can't ask my friend who replaced them because he's gone. Any suggestions? \$\endgroup\$ – Argyle Jan 29 '12 at 7:35
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    \$\begingroup\$ 405nm is actually visible, albeit at or near the extreme limit of what the eye can detect. But just b/c you can see it, though, doesn't mean it's necessarily safe. For instance, I have a 405nm laser pointer, and I swear my eyes feel kind of buggy after playing with it for just a minute or two. \$\endgroup\$ – JustJeff Jan 29 '12 at 20:30
  • \$\begingroup\$ @JustJeff, they should feel buggy, your eyes can easily be burned by UV. Dont use it in a dark room for my own sanity. \$\endgroup\$ – Kortuk Jan 30 '12 at 4:55
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    \$\begingroup\$ @Kortuk, I guess I'm trying to say, even plain old violet, of the not-quite-ultra variety can be problematic. \$\endgroup\$ – JustJeff Jan 30 '12 at 19:44
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The following is based on

  • Personal experience and extensive reading of the relevant literature after my wife burned her eyes with a UV germicidal lamp after following my instructions.

  • Test advice from Nichia re blue light hazard from visible white LEDs


You'd want a proper datasheet and the following is definitely on an "all care no responsibility" & this is my semi-informed opinion only basis, but:

EXPECTATIONS

(1) You'd want to exercise due care when using it on the bench - staring directly at the LED from close range would almost certainly produce a slow but noticeable amount of damage BUT this would probably take hours of exposure to manifest and I'd say almost certainly not less than minutes AND it would manifest as itchy or somewhat sore eyes and would self heal in about a week with no permanent damage.

(2) My real expectation is that you could play around with one of these as much as you wished while setting it up including looking into it across a model from the far side occasionally - and have no noticeable effect whatsoever.

(3) Even worst case you could probably not cause any sort of significant long term damage with anything you would sensibly do with it.

(4) If illuminating a largish area compared to the LED (eg a model) and having it fluoresce and reradiate visibly I'd expect the amount of UV to be at a very safe level.

Reasons to follow

Brief update - more to follow:


REASONS

I understand Kortuk's concern.
I believe that my advice as given is OK (read carefully please) BUT erring on the safe side is always wise.

(1) Background: UV and "arc-eye" & "snow blindness":

People exposed to bright high altitude sunlight for many hours risk being burned by the UV component of the sunlight. A skier at say 6000 feet above sea level who skis all day on a bright day without using eye protection has a good chance of experiencing a degree of "snow blindness". The eyes become itchy and somewhat inflamed. The UV has caused burning if the eye interior - mainly towards the surface. Even people who are exposed so badly that they are literally "blinded" and lose the practical use of their eyes due to soreness and inflammation, will essentially always recover without any permanent effects. Recovery is usually in under a week in typical cases. I've personally experienced minor "snow blindness" on a few past occasions either while skiing or in other higher altitude situations. Wearing eye protection makes much sense.

An identical effect occurs from looking at the arc when arc welding. Large quantities of emitted UV cause "arc-eye" - same result, different name.

Germicidal lamps which emit short wavelength UV In my workshop I have a ~= 20 Watt UV germicidal lamp - in the form of a "fluorescent tube" BUT with no phosphor so no fluorescence just hard short wavelength UV. This kills germs with abandon and will happily burn the insides of your eyes if you look directly at it for reasonably short periods. eg 1 minute would be far far far too long.

Long long ago I used this lamp for bulk erasing windowed eproms (some of us are that old :-) ) and more recently it has been used for etch resist exposure or materials testing.

I have used this light reasonably extensively over many years with no obvious harmful effects. As harmful effects are quite easy to acquire (see below) I assume that this means that taking quite basic precautions goes a long way towards reducing the hazard level.

Diagram: Germicidal versus wavelength of interest. Almost

enter image description here

A few years ago I set up some plastic samples under this lamp, placed a cover over the lamp and samples and left it running. Test time was expected to be many weeks. Some time during the "run" I went to China on business. The UV test results were relevant to what I was doing in China and I asked my wife to report on results to date. I provided detailed & careful written instructions on how to uncover the lamp, how to inspect the samples, how to recover the lamp and, very importantly, how to avoid looking at the light in the process, complete with very clear instructions re the hazards. My wife is a competent and careful science professional (in another field) so I anticipated no problems.

Prescript for the queasy: End result excellent AND they swear that while the UV obviously caused the "arc eye" / "snow blindness", the deeper eye damage was unrelated and the UV damage caused it to be found.

Within a day of checking my test samples my wife's eyes became itchy and sore. After a few days she went to the Doctor who confirmed the obvious. She ended up needing both eyes bandaged due to the severity of soreness and burning. Due to the apparent severity she visited the local hospital eye clinic. The routinely interested examiner suddenly leaped up and ran from the room to get a second opinion. In one eye only she had partial retinal pulling causing a subsurface void near the optic nerve.which would have lead to retinal tearing and separation if left unrepaired. This was subsequently repaired by an epi-retinal peel by a suitably skilled man using very very very small sharp things and lots of experience. (Cut hole in eye ...). It subsequently developed a cataract which was removed with a YAG LASER - shine VERY bright focused light into eye ...).

As one does, I did lots of related reading. The professionals are without exception adamant that the retinal problem was unrelated to the UV. They say macular degeneration of this sort happens with age and that the UV event was a fortunate means of showing them that this was happening. My reading showed that in the very very very large percentage of cases (probably 99.99%+) experience is as they report. UV exposure, even very severe and with short wavelength, does NOT lead to premanent damage or to retinal damage of any sort. However, it was also apparent that in extremely extreme cases (eg welding without a mask long term) then retinal damage almost certainly can occur. This is so rare as to be hotly contested by all experts. I'm also aware that if lensing did cause the arc-eye effect (see below) then the focusing MAY have resulted in a focused retinal spot - but the experts all say NO.

WHY DID IT HAPPEN: Uncertain. She is certain that she followed my instructions correctly and there is every reason to think that she did. But, my wife wears glasses for close vision (or did before her eye sight was corrected as a result of the above processes). I theorise that the very short wavelength UV was refracted substantially differently by the lenses and as she looked across and not at the light, the UV was bent into her eye.

(2) Nichia carried out tests on some lowish power (150 mW in max) white "phosphor" LEDs. In the blue region the output was high enough to make them of potential regulatory interest. I'd guesstimate that you could stare at one of these all day long from 100mm and only get bored.

BUT given this result, an LED designed to operate at about 400 nM at about 60 mW input can be expected to output substantially more "somewhat blue" light than my sample and so would technically at least be of potential interest.

BUT the above example with short wavelength UV and the expert opinion re the lack of permanent effect at even high doses suggests that you are unlikely to have any problems if very basic and simple precautions are taken.

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  • \$\begingroup\$ What about the commenter who said he has an array of "hundreds" of UV LEDs? Would it be dangerous to be in a room with that? \$\endgroup\$ – Matt B. Jan 30 '12 at 13:55
  • \$\begingroup\$ Actual UV light does do damage to eyes and does still give off a very small bit of light that is visible. They do long term damage, I have an honest worry that you might be putting someone at risk with this advice. \$\endgroup\$ – Kortuk Jan 30 '12 at 23:56
  • \$\begingroup\$ @Kortuk - I understand your concern. I have had quite extensive non-professional experience with this by accident :-) :-(. And also some expert advice and I did quite a lot of reading on it as a consequence. I should extend my answer as i said i was going to. Will add a brief extra now. \$\endgroup\$ – Russell McMahon Jan 31 '12 at 1:01
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    \$\begingroup\$ @RussellMcMahon, I would appreciate that. I may be misinformed, which I always must accept, but our UV setup for etching was warned as very dangerous to eyes, although did not use UV LEDs. \$\endgroup\$ – Kortuk Jan 31 '12 at 1:30
  • \$\begingroup\$ @Kortuk - Long spiel appended. Don't try that at home :-). \$\endgroup\$ – Russell McMahon Jan 31 '12 at 2:25
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I wouldn't worry too much about LEDs in this category. UV LEDs are thought to produce ultraviolet radiation that can be harmful to the skin, eyes, or other bodily organs. The truth is the radiation emitted is called "near UV," and it occurs below the threshold of harm posed by the true UV wavelength. These LEDs are near ultraviolet at 405nm, where the ultraviolet wavelength starts at 400nm - a tad shorter wavelength. The type of LED you're using even at maximum voltage of 4.5 VDC at 30ma will have a power output around 135mW. Not a real significant amount of power. With that said, I wouldn't stare into one for long periods of time.

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    \$\begingroup\$ I'll be commenting in my answer, but, it is highly likely that this LED constitutes a Class 1 eye hazard, at least. I have a WHITE LED rated at 3V, 50 mA that was formally tested by Nichia for me and which actually warrants attention in the blue to near UV region - despite being THE most efficient WHITE light producer for sale on earth in its class. If that applies to a white light producer its liable to apply to a greatyer extent to a near UV source. That said, I don't think it's much of a real world hazard. \$\endgroup\$ – Russell McMahon Jan 29 '12 at 10:50
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UV has negative effect on eye lens. Couple of years ago, I've used this UV LED for excitation in a fluorometer. For that project, I've bought industrial protective glasses with UV protection (American Allsafe Co. p/n 19159). Regular commercial sunglasses with UV protection would have probably done the job too.

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    \$\begingroup\$ Actually even normal corrective glasses have got UV filter, not just sunglasses. \$\endgroup\$ – Al Kepp Jan 29 '12 at 20:16
  • \$\begingroup\$ @AlKepp - Normal glasses do have a UV filter, but when you're working with high-power UV, you want something a good deal heavier. If you're doing something like UV-curing epoxy, or exposing PCBs, or anything else with dangerous levels of UV, get yourself glasses for that job. \$\endgroup\$ – Kevin Vermeer Jan 31 '12 at 4:14
  • \$\begingroup\$ @Kevin Vermeer> Why do you think regular sunglasses have better UV protection that regular corrective glasses? I'd expect that prescription corrective glasses are generally much higher quality, including better UV protection. The fact that sunglasses are dark doesn't protect from UV at all. \$\endgroup\$ – Al Kepp Jan 31 '12 at 11:28
  • \$\begingroup\$ @AlKepp - I didn't suggest that sunglasses are better than corrective glasses. I was agreeing with Nick about the use of industrial protective glasses, like some of these Dymax ones. \$\endgroup\$ – Kevin Vermeer Jan 31 '12 at 13:14

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