# High Pressure Sodium lights?



## BatteryCharger (Sep 12, 2005)

I bought a used 250 watt high pressure sodium warehouse light type fixture. I plan on making a really big spotlight with it. (28,500 lumens ) I was told that an HPS fixture needs to be completely enclosed because the bulbs can explode. Is this true?? Also, do I need to be careful to keep all fingerprints off of the bulb?


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## IsaacHayes (Sep 12, 2005)

I'd say yes it's true to both. Clean it well with acetone something that will remove oils. And if it's high pressure, well, it can explode obviously..


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## Zelandeth (Sep 13, 2005)

HPS (Or to give it its correct prefix SON) bulbs should be treated with respect - but not to the extent of being terrified of them as with some of the compact metal halide ones or quartz-halogen incandescents.

The outer bulb of most SON lamps is normal glass - and is there specifically to protect the arc tube (which is made of polycrystalline alumina by the way) from the atmosphere, and to prevent the seals from oxidising. 

Contrary to the name, the arc tube is actually well below atmospheric pressure, and the outer's under a hard vacuum. The worst thing a SON lamp's likely to do is crack and die if dropped. They're not likely to explode. I've seen several now where the inner arc tube's ruptured, but not done anything to the outer. A huge number of SON fixtures have open or wire mesh fronts. These bulbs are pretty safe.

The high pressure part referrs to the elecrical loading of the arc I believe. Though the gas filling is of a higher pressure than of the low pressure (SO/SOX/SLI) types.

As with all lamps, treat it with respect, but no need to be afraid of this one.


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