[bowfront]

Thanks Ninong. I've read that article before but unfortunately Sanjay started his testing at 310nm so it doesn't really give an indication of UV-C (if there is any) or complete UV-B. In his more recent article in MFAR 2002 annual he started his tests at 300nm for the 150w HQI. What would be nice is a complete run for HQI DE's both with and without shields. This might help to clear up some of the confusion.

[Ninong]

I believe the reason Sanjay used a shield this time on the 150w HQI DE lamp is because he cautions people to never operate the DE lamps without a shield.

I am positive that I have read somewhere that the 10,000K HQI DE lamps emit a small amount of UV-C but I can't remember the source right now. It was in the context of a warning to always use a UV-absorbing shield.

Ninong

P.S. -- While looking for that UV-C reference on DE lamps, I came across this recommendation by Robert Fenner concerning shielding for all metal halides: http://www.wetwebmedia.com/lighting1MAR.htm

Shielding

Was just mentioned in thermal terms. Also of concern is life-damaging ultraviolet light produced. Real fast here; U-V light is classified into three types on the basis of wavelength. In nanometers these are:

UV A: 320-400 nm, UV B: 280-320 nm, UV C : 200-280 nm

Some UV "A" range is useful, necessary for some light-using life; "B" and "C" are dangerous/harmful. UV "C" is absorbed by the planet's celebrated ozone layer; within it's band, 257 nm is the energy produced by UV sterilizers. UV "B" can be halted by glass and water, is very destructive to nucleic acids (life) and photosynthetic activity. UV "A" is effectively filtered out for the most part by special filters and bulb coatings provided by manufacturers. I only will install and address the use of metal halides with the use of UV filters, even though they may coated/engineered to be used without them. This added protection against radiation poisoning may require more shielding action and periodic cleaning, but is well worth the "cost" in preventing you and your livestock from "burning". Also of concern is the explosive effect of these 'high-pressure' light sources getting splashed, broken by splashing water, or cumulative bubble-mist.

[bowfront]

Ninong,

That's interesting. I wonder how tempered glass works as a shield for UV-C? If you come across anything more in regards to the amount of UV-B or UV-C produced by de bulbs please post it or email me. Thanks

Charlie

[Ninong]

Bowfront,

We can probably draw some conclusions from the fact that 3/16" thick regular glass absorbs 27% of UV-A and 97% of UV-B. UV-C is even shorter than UV-B. I am guessing that it is easier to block.

Ninong

[bowfront]

Ninong,

If you look at the thread that you were involved in with Eric B. concerning HQI shielding you will notice that Tatuvaaj from Tampere, Finland posted some information regarding UV-C levels in 250W HQI bulbs. Here’s a compilation from two of his posts. It looks like according to Osram there is some UV-C released by these bulbs.

From Tatuvaaj on Reef Central:

HQI lamps should never be operated without a protective UV shields. The lamps emit non trivial amounts of UV-C which is deadly (and unnatural) for both aquarium organisms and humans. It is the wavelength UV sterilizers use. HQI bulbs also emit UV-B and UV-A.

You want to shield yourself and aquarium organisms from all UV-C radiation and most UV-B radiation. I understand that UV-A is present in nature in a large amounts so that might be a lesser concern.

As for references, just look at any instructions published by HQI lighting manufactures or for example OSRAM's data sheets. I don't have either in front of me but this has been a common knowledge in Europe for a long time. HQI fixtures are always sold with UV-C shielding glass!

Only reference I have right now is original "Korallrevs akvariet" by Fosså & Nilsen, vol 1. On page 46 there is a table that references OSRAM databook and it clearly shows that HQI lamps produce all types of UV radiation (A-C).

HQI 250W (at 1000 lumens):
UV-C 29 mW/m2
UV-B 108 mW/m2
UV-A 900 mW/m2

[Ltspd]

Here is a copy of the email I have sent to Viracon Glass. Hopefully we can attain some definite information as to the amount of blockage of each UV ray.

Mike,

I am looking to aquire further information in regards to the UV blocking capabilty of the uncoated monolitihic glass. Your companies website denotes that there is a 62% pass thru for UV glass in the 1/4" clear thickness. I need to determine the amounts of UV-A, UV-B, and UV-C amounts that are blocked. I intend to use this glass in a tempared form as a heat/UV shield for double ended metal halide bulbs. The output of UV's of these bulbs are as follows:

HQI 250W (at 1000 lumens):
UV-C 29 mW/m2
UV-B 108 mW/m2
UV-A 900 mW/m2

If possible please provide me with any further information your company may have in regards to the seaperation blockages of UV rays.

Thank You,

Paul Christopher
Design Engineer
Highland Machine Works, Inc.
(828)681-8700
(828)684-6611 fax

Schott glass's website is down but I will be sending a email to them also. I will post that email to once it has been sent.

[Ltspd]

Not much but a response.

DAN,

DO WE HAVE ANT INFO ON THIS? IF SO COULD YOU FORWARD IT ON TO MR. CHRISTOPHER.

THANKS,

MIKE

This is the Mike of the last email

[Ltspd]

Provided by Viracon Glass

1/4" Clear glass

Wavelength Transmission

300 nm 0.0%

305 nm 0.0%

310 nm 0.1%

315 nm 0.7%

320 nm 3.5%

325 nm 10.7%

330 nm 22.8%

335 nm 37.5%

340 nm 51.5%

345 nm 63.2%

350 nm 71.8%

355 nm 77.8%

360 nm 81.7%

365 nm 83.8%

370 nm 84.4%

375 nm 83.0%

380 nm 82.4%

385 nm 84.2%

390 nm 86.2%

395 nm 87.2%

400 nm 87.7%

[Ninong]

Excellent! Thanks, Paul.

Just what I suspected. Now we know why AB-Aqualine is content with 3/16" tempered glass as shielding material.

That data would indicate that there is no transmission of UV-C and only an extremely limited transmission of UV-B, and even that tiny amount is at the upper end of the range of UV-B.

Ninong

P.S. -- Those numbers seem to confirm the measurements that Dana Riddle published in his UV article.