Article, the dangers of Metal Halide bulbs
 

Found this on web:

http://www.suburbanchicagonews.com/h...LBS_S1.article

How many of us venture into old warehouses and see these things. Makes you wonder.

Yes, its true and it's why I'm engineering my hardlight series (which will be ceramic metal halide) to all have lenses with UV protection. No open face CMH for me, I'd rather sleep well at night.

By the way, this is the reason HMI / CMH give off more heat even though they are in some cases more efficient than fluorescent (80 to 140 lumens per watt): UV. UV is the culprit in heat emission from many kinds of bulbs. So it's hard to classify CMH as one of the "Cool Lights" but it is certainly cooler than tungsten.

Richard, how about LED lights? I think I read somewhere that the way white light is generated is by using a UV LED with something like phosphors that iridesce the visible spectrum. Does this mean that a white LED can emit significant UV?

If not, I want one of those 60W LED lights! :)

Marcus, some LED's emit UV and some don't. I'll ask that question about the 60w one but from what I've seen and heard about it so far the answer would be no. It runs pretty cool too.

For example of some that do emit UV, there's an LED from a company named Nichia that emits UV to excite phosphor (sound familiar?) as a replacement for current fluorescent technology. No electrodes so bulb life goes way up.

On that 60w LED, I hope to have it in a fixture very soon. The fixture we've chosen looks like a small Arri pepper fresnel with barndoors and gelframe included. I'm wondering though whether a spot lens might not be more appropriate than a fresnel lens, so we may try one other fixture and/or lens before we get the optimum one. When I have it all together I'll post some pictures.

I guess you guys never heard the story of the Norwegian Prince and Princess Haakon and Mette-Marit being burnt by an HMI light in an interview with the German newsstation n-tv in 2002...

I found an old article on this (in German) http://www.abendblatt.de/daten/2002/05/13/23228.html

In short it says that both the Prince and his wife suffered from extremely heavy sunburn, the princess additionally suffered from a uv-burn on her retina.
The interview was filmed on the outside, in the sun, however the sunburn appeared only on the opposite side of the sun where the HMI fill light was placed. A lighting expert said that usually these HMI lights are safe, the only case something like this could happen was when the safety glass on the light was missing or broken... :)

Thanks for that. I never heard that story. But your link is in German so I'll have to take your word. ;-)

Just goes to show what I'm talking about. There are three types of UV radiation in the UV band of light. UVA, UVB and UVC.

Also, the research I've been doing shows that the borosilicate glass on the front of most pars and fresnels actually is more efficient at transmitting UV than regular glass. Perhaps that's why they use such high quality glass is because it transmits light across the spectrum whereas regular window type glass or "soda-lime silicate" as its called actually blocks UVB pretty well by itself but still allows UVA through. All glass apparently blocks UVC.

As far as I'm concerned, what this all means is that many of these HMI may be unsafe unless they built in some extra protection at the level of the lens. What if the original bulb had a glass outer protection shroud but the replacement the user finds is cheaper and doesn't have it? Some bulbs do and some don't. Unless the lens or an extra lens with protection is built-in, bottom line is you can't guarantee that your HMI lighting instrument is safe.

Marcus,

I checked with the product engineer and there is no UV emission from the 60w LED.