Just curious

At my job, I sit at a desk. The office opens onto a fab shop; welding
and machining. So, there's a weldor right outside my office window
(yeah - weird - the windows in my office looks into the shop), and
I'm wondering - Obviously, looking at the arc will hurt my eyes, so
I don't do that. But I'm wondering - when the light from the arc
is reflected off the walls, other areas of the weldment, his hood,
etc - is there any danger from looking at the light that's reflected
off those surfaces? Or is most of the UV gone by then. It's not
uncomfortably bright, but UV is invisible, after all. (sometimes
when I walk by, I can smell the ozone.)
Reply to
Rich Grise
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I recommend wearing a welding helmet at all times when in that office.
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mattathayde had written this in response to
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------------------------------------- Rich Grise wrote:
i would be looking at some form of protection, the glass might knock out enough of the residual UV that is bouncing around but i wouldnt count on it. as to my understanding UV really isnt the issue as much as IR is, which again if i understand correctly takes more than just glass to knock out much (hence the reason for the special welding shades). ive had a friend standing in our metal shop while some was welding with a wire welder behind us and the reflections off the walls and all caused her eyes to become very very sore after just a few mins (she does have very sensitive eyes though)
if it was me i would get blinds for the office or wear a welding shade all the time
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Yeah, it could be dangerous if you are exposed to those reflections for the long term. It all depends on how much reflection and exposure you are getting. If the arc from welder is shining right in your window (he's using nothing to block his arc from you - then you are in danger). If the only light is the reflections off the work area around the welder, then the risk is not as great, but is still not good for the long term. You should probably do something to protect yourself.
What type of glass is in the windows? It might already be protecting you. Polycarbonate plastic (used in many types of glasses and safety products and used as the protective cover plate in welding helmets) is a great UV block and if your shop windows are already made of polycarbonate, you are probably safe. If you wear glasses with plastic lenses they are likely to be polycarbonate as well, which would also give you even greater UV protection. Real glass doesn't block much UV I don't believe, but if you have real glass windows, you could just put a sheet of polycarbonate plastic over it and that would likely cut down the radiation to a safe level while still allowing you to watch what was happening in the shop. You can also put protective window film on the glass to block the UV (from places like Lowes to block heat).
If you don't need to see the shop, you might consider just blocking the window.
If the flash you can actually see is distracting, you could try and find some shaded material to cover the window with but it would of course reduce what you could see in the shop as well. Lowes I see has shaded window film for cheap, but the shaded stuff only blocks 95% of the UV instead of 99% of it.
Just wearing clear safety classes as well (almost always made out of polycarbonate) would greatly help protect you from UV reflections as well.
Reply to
Curt Welch
Thanks to you, Curt, and also Matt and Iggy.
They do have canvas curtains, so there's no danger from the direct arc, and I have plastic-lensed old-guy glasses that I need for the computer, (and the newspaper, the microwave oven display, the dial on the toaster oven, etc, etc, etc. ;-) ) still, I'll do my best to minimize watching the glare.
Thanks again! Rich
Reply to
Rich Grise
It's like the army. If the enemy is in range, so are you. That is an unsafe workplace. Both the workplace, and the place (desk) you work at. I'm not up on OSHA any more, but if you can see the arc, or the bright light it produces, I'd say you're being exposed to something you shouldn't.
Now, will you go blind next Tuesday? Probably not, but there are a lot of times in my life that I was exposed to stuff when I was young and stupid and ten feet tall and bulletproof that now I wish I had been more careful about.
Don't know about where you work, but where I worked, if you went blind, you had to go home.
Be safe.
Reply to
The upside is no one can tell if you're awake when you have a helmet on.
Steve ;-)
Reply to
You might try cheap automotive window tint, it's cheaper than ordering a shade 5 lens the size of your window.
Reply to
If you haven't gotten flash burn by now don't worry about it. Intensity drops off as the 3rd power of distance.
Reply to
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Reply to
There should be an orange curtain on his side in front of the glass. This could cost you eyesight or anyone that comes in.
If OSHA visited - heads would roll.
Until the curtain is installed - wear a auto welding helmet. Martin
mattathayde wrote:
Reply to
Martin H. Eastburn
yep,yep. Never underestimate the power of human stupidity.
Reply to
Sometimes, the magnetic field from a 360 Amp arc distorts my monitor. :-)
Thanks, Rich
Reply to
Rich Grise
Glass attenuates UVB but does not attenuate UVA to any great extent. Polycarbonate attenuates both. Talk to you safety rep about it. If your windows are glass, adding some polycarbonate will also add protection to keep the windows from being broken.
Reply to
Apart from the chemical, electrical, thermal and mechanical hazards, a welding arc emits IR, visible and UV light. All are potentially harmful, in different ways.
IR: For a welder, IR can heat the skin, and the layers under the skin, and cause burns. This only happens up-close, and isn't a factor in your situation.
IR can also cause eye damage including partial or full blindness; apart from causing cataracts, if focussed on the back of the eye IR damages the receptors and nerves by heating them up, but it takes a lot of hot, near-visible IR to do that (long wavelength IR is absorbed by the cornea and lens, causing cataracts instead).
However a welding arc can put out a lot of short wavelength IR, and this focussing may be a problem if you can see the arc directly.
This can cause damage over a considerable distance if the IR is focussed on the retina.
Visible: Eyes adapt to with cope with brightness by shrinking the pupils, changing the sensitivity of the retinal layer, partly closing the eyelids, and by squinching up the area around the eyes - but up close a welding arc is just too bright for the human eye, which can't adapt enough to cope, and the bright visible light from an arc can bleach and/or burn the retina.
Even at a distance the visible light from an arc can be very damaging, similar to the second IR danger above, especially if the light is focussed on the macula (the macula is the central part of the retina, where you see best).
This is because the amount of adaptation the eye does is dependent on the total illumination, not the brightness of the spot, and if only one spot is very bright when most of the rest of the visual field is at normal levels then the adaptation of the eye will be small, allowing lots of light from the bright bit to pass through the pupil and be focussed in a spot on the retina. It's worse when the ambient light level is low.
In the case of an arc, this is a mixture of visible and IR light, and the effect is similar to when someone goes partially blind from looking at the sun, only it can be quicker.
Imagine focussing the sun into a spot with a lens - now imagine doing the same with an arc, and the bright spot is in the sensitive part of your eye where you see best ...
Even if the damage is temporary, just a black spot for a few minutes, it's still damage, and it will come back to haunt you in the long term.
For this reason, no-one should *EVER* look directly at an arc without eye protection, even from a distance.
MIG is apparently more dangerous than stick or TIG for this, and oxy cutting is worst of all. Reflected arc light can be just as bad too, or even worse. Usually of course it's less dangerous, but you won't always be able to tell ...
UV: UV causes the reddening of the skin/sunburn associated with an arc, tanning, arc-eye, conjunctivitis, skin aging, and skin cancer.
Distance will attenuate the effects of UV quite rapidly - the long-distance focussing effect mentioned above doesn't happen with UV, which is mostly stopped by the conjunctiva and cornea of the eye before reaching the retina.
It was once thought that UV was absorbed in the lens too, leading to welder's cataracts - however nowadays many people think that UV is absorbed in the conjunctiva and cornea only, and that welder's cataracts are caused by IR rather than UV. I'm not really up-to-date on this point though, and afaik there are still arguments about it. I suppose it could be both ...
(That's how you can get arc-eye without going blind btw, the UV is absorbed by the cornea and inflames it, If the UV reached the retina and was in focus, it would blind you very quickly indeed)
UV is usually divided into four bands, only three of which are found in arc light - UVA, UVB and UVC (the fourth is called vacuum UV).
A bit over half the UV from an arc is UVA, the rest is mostly UVB with a little UVC. The latter two are a lot more damaging than the UVA.
However a 4mm sheet of ordinary soda float window glass will cut out around 98%-99% of the UVB, and all of the most damaging (but sparse) UVC.
Like UVB/UVC, UVA also causes damage, but not as much - it's the kind of UV in a sunbed, it doesn't cause sunburn nearly as much as UVB/UVC, but it can still cause arc-eye.
Also UVA is probably as carcinogenic as UVB/UVC, indeed there is recent evidence to suggest that UVA actually causes more melanomas than UVB+UVC.
A sheet of glass will cut out from 10% to 90% of UVA, depending on exact frequency etc - but on average, say half of it gets through. You can get UV glass or films to stick to ordinary glass which cut out almost all of the UVA (most glass is already almost entirely opaque to UVB and UVC).
If you are a reasonable distance away from the arc, especially through a sheet of glass, the UV isn't going to cause much direct trouble in terms of blindness, itchy eye or sunburn - though it may increase the chances of skin cancer, especially if exposure is long-term and continuous.
Summing up;
1) Don't ever look directly at an arc. or a reflected arc, even from a distance, without eye protection.
2) Avoid getting to close to an arc unless necessary, and if you do get close, cover the skin and protect the eyes from IR, UV and brightness.
3) Avoid any sort of unprotected long-term and continuous exposure.
-- Peter Fairbrother
Reply to
Peter Fairbrother
Forgot to add the notes, sorry.
[a] An arc can damage the retina quicker than the sun in this way for three main reasons.
First, an arc is, or can be, brighter than the sun, and our eyes are only adapted by evolution to cope with the brightness of the sun, as nothing brighter exists in nature. Even the sun is too bright for extended direct viewing, one reason for brows and eyebrows is protect the eyes from the sun.
Second, the atmosphere reduces the light and the near-visible IR from the sun, but this doesn't happen with an arc as there isn't miles of air in the way.
Third, when you look at the sun it's usually against a bright sky and your pupils will be small - however when looking at an arc the background may be fairly dark, and the pupil will consequently be large, allowing more light, both visible and near-IR, to enter.
[b] This is because UVA is absorbed in just the right, or wrong, place to cause cancers, and especially the most life-threatening melanomas, at the dermis and basal layers beneath the surface where the skin is growing and the skin cells are dividing.
UVB tends to get absorbed more in the outer, dead or non-reproducing keratinising (where the cells are changing to keratin) layers of the skin, and doesn't reach the reproducing basal layer or dermal cells as much as UVA does.
UVB can and will cause sunburn, and some other skin problems including cancers, but 92% of melanomas are definitely not caused by UVB, and we're not sure how many, if any, of the remaining 8% are.
UVC from the sun is mostly absorbed by the atmosphere, and isn't found in quantity in nature. Consequently we have little evolutionary defense against UVC in an arc, but fortunately it seems UVC also tends to be absorbed in the outer, dead, layers of the skin.
Reply to
Peter Fairbrother
I had never heard the term "float glass" before. After some Goggle research I now know a little more. That's cool. I thought window glass had been made basically the same way for the past few hundred years, never had a clue there was a major technology change only 50 years ago.
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Trying to find the transmission properties of typical glass proved difficult however. The only graph I did find:
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Seemed to indicate that about 80% of UVA (320nm-400nm) and maybe 50% UVB (280-320) rays would make it through, and not hit near bottom until around 250 nm which is in the UVC band (100nm-280nm).
I have no clue how accurate the graph is (or how accurate my reading is since it's not well graduated down at that level of the scale.
All very interesting stuff however.
Reply to
Curt Welch
Not very accurate at all, I'm afraid, though the graph is mostly to blame. Here's a somewhat more accurate graph:
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There's also a much more accurate graph here, with graduations in approximately the right region, from the Tate museum:
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The 98-99% figure I gave for blocking of UVB is a working average - it actually varies between about 97% at 320 nm, and 100% at 280 nm.
I think so, though it may be getting a little off-topic here :)
-- Peter Fairbrother
Reply to
Peter Fairbrother
Yeah, both those graphs are more likely to be trusted since they are scaled and crated for the purpose of showing UV transmission - and both seem to indicate 85% or above blocking of UVB for "standard window glass".
Reply to
Curt Welch
And I'm skeptical, since there were "acceptable levels of asbestos exposure" and those were published by the government. Just like the troops they marched out to watch the A bombs in the desert. "Acceptable levels of radiation".
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