Unsafe UV from high-power tungsten halogen in office?

|> Would it be safe to use a 300 Watt tunsten halogen floodlight as a |> good bright light in my home office? |>

|> This would be on for approx 8 hours a day. I'm wondering that maybe |> after that sort of exposure the extra UV could become a significant |> adverse effect on eyes & skin. | | To answer your question -- yes, tungsten halogen lamps do emit substantial | amounts of UV and they are perfectly capable of causing skin and eye damage | if you are directly exposed to the light of an unshielded lamp. In Italy | some years ago, users of small halogen task lamps reported sunburn and other | UV-related problems because the lamps were not shielded. | | But a piece of glass will filter the UV to minimum levels and the halogen | lamps should be enclosed anyway in case of bulb rupture. You definitely | don't want to experience that in a home office situation. | | As others have said, however, there are much better, more efficient and | safer ways to light your office using fluorescent lamps.

I'm looking for a way that results in a uniform continuous spectrum. I have found that fluorescent does not accomplish that. Also, LED does not, either. But I think there may be hope in that LEDs are available is lots of different wavelengths. A mix of a lot of these could come close to the continuous spectrum.

NIST has a current project to build an LED lighting system that has sources which emit at every 5 nm (I think). Each "color" would be individually controllable in output. What I didn't understand when I heard about it is how they expect to find or tune LEDs to the various wavelength bands.

Terry McGowan

The information is a bit hard to find, but it's out there. The lamp manufacturers' catalogs are the best way. For example, go to the fluorescent section of GE's catalog at :

Terry McGowan

Well, yes... but good fluorescents come at least that close. Look for tubes with a colour rendering index of at least 90. They will be referred to as "colour 9xx", where the second two digits refer to the colour temperature. These tubes are usually not as bright as standard ones, but offer a smoother spectrum.

Off the top of my head, one such range is Osram's "Lumilux Deluxe", at least in Europe.

Osram and Philips have both recently brought out another range of tubes with *really* good colour rendering (CRI of 98 or so), but they're pretty dim for the power input. The Philips one goes by the name of "Graphica" in Europe, I can't remember what Osram call them. ISTR that they're only available at a 6000K colour temp or thereabouts, and I

The problem is usually not the amount of UV coming out of the lamp; it's not knowing that you are being exposed to it and taking proper precautions. When people switch on a desk lamp, they don't expect to get "sunburned" from the light.

Terry McGowan

Important information. Such cases have occurred since mercury HID lamps started to be used for indoor industrial and commercial lighting about 1965. There have not been massive problems; but since people are injured, any incident gets attention. The safety device inside the lamp has appeared to work well (when the outer bulb is broken, outside air causes the safety device to open the arc tube circuit); but anything can fail to work. I've always promoted the use of enclosed fixtures for such installations, but users complained about the higher cost and sometimes the enclosure glass was broken or not replaced when the fixture was serviced. The maintenance people must also know enough about the risk to install the lamps with safety devices as standard lamps will also work in the sockets.

The industry/government has not found a 100% solution to the problem -- most due, I would say, to lack of knowledge/education and concern about costs. Unfortunately, it takes a large lawsuit sometimes to get proper attention.

There was a similar problem with exploding metal halide lamps some years back. The problem was understood, fixes were developed; but no foolproof solution was implemented. Then the problem got massive attention after a major lawsuit was lost.

Terry McGowan

On the other end of the visible spectrum, you can get "IR detector" cards printed with a special ink or dye. You leave it in normal light for a little while, then shine infrared light on it (like from a TV remote control) and it lights up. Is anything like this available for UV? I'm thinking of a small, inexpensive card that could be taped to the wall in rooms with mercury HID lights, with simple directions like "if the blue spot printed above turns red, please check the light fixtures."

I'm sure you could build an active circuit for it, but then you have to get people to change the batteries. If they won't put batteries in smoke detectors or maintain light fixtures correctly, they probably won't put batteries in the UV detector. On the other hand, not mantaining the fixtures might be explained by having to haul things up and down a ladder, where changing batteries in a device mounted at eye level on the wall is easier to do.

Matt Roberds

Good idea. I've heard of such detector "dose" cards; but I haven't tried any. There's a debate building about UV exposure. Some UV is good for people -- vitamin D, natural sunshine and all that. Some say people don't get enough these days to ward off rickets, big diseases and even common colds. Others say UV=skin cancer. End of story. (I'm overstating , of course :-) But, maybe there are facilities such as hospitals, retirement homes or even schools in the far north (or south) where UV from sunlight is zero for much of the year and where we might want to add some UV to lighting in "sun spaces" or light therapy rooms. If so, a dose card on a person might ensure that a person gets their proper amount. Enter "Michael F. Holick" on Google if you want to read about some the pro-UV research.

Terry McGowan

I assume There's UV and then there's UV, meaning that energy at some UV wavelengths may indeed be beneficial while energy at others other may indeed be harmful so we probably need to be more specific about the radiation than just "UV." One of Holick's books is titled just "UV" but in the one Holick article I read he refers to UV-B, which is a bit more specific. I wonder if Vitamin D production is even more specific than UV-B.

Well, it could be light powered and bleep at you when there's a problem.

Or something that discolors with UV, but that will take time to react. Fluorescence could work, but I do have no idea how large the UV part is and how efficiently this can be converted. When glass of quinine-flavored soft drink turns green, check the lights. Just needs a filter to keep visible light out except for the viewing hole.

Thomas

Materials that Fluoresce under UV light come in different flavors. Some are sensitive to long wave UV and others will light up only under short wave UV. There is also a mid-range value.

Rock collectors who collect samples know this well as they frequently must use a lamp with a combination of UV wavelength outputs (or multiple lamps).

Beachcomber

Zak correctly noted something I should have caught... if the point is to measure UV light from interior lamps, there is also probably enough visible light to run a solar cell instead of using batteries.

I Googled and found some; these seem to be sold more for checking industrial processes that use UV light, but could probably be used as "dose" cards. One example is at the hideous URL

Sounds reasonable to me. I might add some kind of active detector for the whole room to help catch any problems with the artifical UV.

I did and it was interesting. I'm inclined to agree with him; laying out on the beach at the equator for twelve hours every day is probably not good for you, but neither is getting no unfiltered sunlight whatsoever.

Matt Roberds

AFAIUI there isn't anything complicated here. The more UV, the greater the risk of skin cancer. However too little UV doesn't allow Vitamin D generation, and probably has other side-effects too. At some point there will be a sweet spot where the total risk, including that of death from skin cancer and that of death from lack of UV[1] is at a minimum.

This sweet spot will depend upon the individual's skin colour; this is not, of course, coincidental, but is the evolutionary reason that races from different latitudes have differently coloured skin.

-S

Don't forget to allow for area of skin exposed and ratio of such area to total body size.

And of course exposure outside of the monitoring process. Any dosing card is usless unless worn whenever exposed to ANY UV source!! ;-)