Filter for metal halides?

[kstuber]

I've been running a retro-fit fixture, where the bulbs are just out there. No glass encasing the fixture, etc. The bulbs and literature say the animals and humans are getting unfiltered UV if not using a "filter". I'm supposed to use a filter for the UVC they say. Questions:

1) Where can I get a "filter" for a retro-fit? Not even sure what this looks like...
2) The skin-care industry stresses blocking the UVA & UVB. No mention of UVC. Can anyone share light on these different statements?

 

[Anonymous]

It depends on the bulbs. Many of the new brands are made with UV absorbing glass. This means there is no need for an additional filter. This does not hold true for HQI/DE bulbs, they need a lense to shield UV light.

 

[Anonymous]

Are the mogul, or screw in bulbs? If so the outer envelope is glass, and you don't need a filter. UV mostly cannot get through glass.

If you have those little double-ended or "HQI" bulbs, you need a protective glass.

 

[Anonymous]

UVA is fairly benign, UVB causes sunburn, and I guess UVC is worse but its mostly filtered out by the ozone layer. Not sure if it is present in halides.

 

[kstuber]

They're mogul base. Ushio UHI-175 10,000K. I've been using these and "true" 10,000K bulbs for about 6 years now in a Hamilton retrofit. The hood was purchased before I planned on a reef tank, and as such is only about 7" high. I used the retrofit and installed 5" fans at either end of the hood to blow across the lamps and water. I originally used 1/4" acrylic custom-made covers to prevent splashing on the bulbs, but even with a 5" fan blowing on the sump, the heat build-up was too much. In avoidance of purchasing a chiller (space, noise, cost), I removed the covers shortly. Also removed them due to light blockage (not noticable to my eye, just from what I'd read at the time.)

Sounds like the UV isn't a huge concern with these bulbs, but exploding is. I knew this latter risk, just not sure what other options there are.

 

[Wheeldog63]

If you are using the USHIO Mogul-Base bulbs you do not need a screeen or a filter, that is contained in the glass that surround the bulb, the HQI or double ended bulbs needs the UV glass because they do not have that external one built it.

 

[Anonymous]

As long as the outer bulb is not broken, for a mogul-base bulb like yours, no UV filter is needed.

Regular glass will block UV quite well. Glass that does not filter UV is more expenisve (quartz), and only used in special application, such as the inter bulb of the MH bulb and double ended bulb.

 

[kstuber]

Thanks so much everyone! I was getting a bit panicky after reading something about UV radiation. Thinking how many animals have been harmed, as well as what I would look like in a few years after 6 years of exposure! Oh yes, and whether I would be able to see or not! So, anyway, I appreciate everyone's insights.

 

[liquid]

Glass will easily filter out UVC. Heck, standard window glass alone filters out about 85% of all UV to begin with (100% UVC, most UVB, and some UVA). Polycarbonate will take you one step further and will filter out just about all except some UVA.

Shane

 

[Anonymous]

I will need to check, but I think polycarbonate (Lexan) does not do a good job in filtering UV per se, but it is the UV stablizer that they add to the plastic that give the overall plastic the property.

 

[liquid]

Polycarbonate has an inherent ability to filter UV. They do have variations that have UV blockers added to them, which might help in your case. Pure polycarbonate will filter 100% UVC, almost all UVB, and some UVA. UVA's one of those nebulous ones to filter since it's so close to the visible light spectrum.

We use it for that specific reason in UV curing of coatings. The MV and MH lighting we have in our facilities have polycarbonate filters on them so as not to gel any of our coatings and from what we spec'd in they do not have any sort of special UV blocking additives added to them.

Shane

 

[Anonymous]

Let's see...

So from this spectrum, it is good for filter anything less than 375nm, which is around where UV-A (315nm to 400nm). I guess I just verified what you said, liquid.

 

[liquid]

Yeah that's the graph I was looking for! I couldn't find it thru Google for some reason. heh

Shane