Dave, gailgrove is right. ONLY the high wattage bare double ended MH lamps, produce dangerous short wave UV radiation.
The double ended compact MH lamps with quartz outer, don't produce any dangerous short wave UV radiation, because like halogen lamps, their quartz outerbulbs are doped with materials that prevents the UV radiation to escape.
Compact quartz jacketed double ended and miniature 2-pin single ended MH lamps, require an enclosed fitting, only to contain the quartz pieces, should explosion would accur.
Their UV emission is similar to the screwbased MH lamps with glass envelope and the mercury lamps (Mainly long wave UV radiation).
I rather take Dave's side here. The wattage doesn't matter much. Quartz has the property to transmit ultraviolet radiations. Only glass (sodal-lime, borosillicate) blocks UVs enough to be considered as a safe UV shield.
Dor123, keep in mind that European and American standards are not necessarily similar. In North America, double-end MH lamps are made of quartz, so they need a shield to protect the surroundings both from UV radiations and eventual lamp rupture.
Dor123 is right,
These rather low wattage lamps do not emit UV, as the quartz is doped (so unlike the burner), include north american market, the shield i necessary solely for explosion containment (an of course lamp protection).
I think UVC do not emit any of them, neither the high wattage ones, UVA and mainly UVB are supressed below the safe limit.
The blue radiating stuff on the outer (visible just after power ON) is the fluorescence of the UV absorbing doping, what when excited by the UV emit a bit of the blue radiation. Normal, UV transparent, quartz would not radiate in this blue...
Vince, in Europe, double ended compact MH lamps also have a quartz outerbulb, but they produce little UV, because the quartz outerbulb doped with metals that abosrbs the UV radiation. Their enclosure is only to prevent damage in the case of an explosion. Sean is right, that this is the reason of the blue glow of the outerbulb, when the lamp is on.
Also, the glass used in non compact screwbased HID lamps isn't a borosilicate glass, but simply a hard-glass, since they shouldn't be exposed to the outdoor conditions, or the outerbulb will shatter (Thing that wouldn't accur if they would be made from a true borosilicate glass, which can withstand to thermal differences and willn't shatter because of this [The pyrex glass is from the borosilicate family]).
I remember something! Sometime in the late 90s Philips introduced the Fade-Block technology that blocks out UV radiation. I just didn't know it was applied to these little compact MH lamps. The purpose of this is mainly protect items from fading under MH lighting, as well as safety.
In fact the "fade block", "UV stop" and other "UV block" technology was first applied to these compact metal halide lamps by Osram in the mid-1990s, and this technology was applied to other lamps as well in the following years.
If I see correctly, it is the round ceramic arctube. These would use the UV-blocking outer (they are not as old design to be made without the UV blocking doping)
But usually the presence of the UV blocking feature is stated both on the lamp etch, as well as on the package.
The UV LED would not be reliable, as LED's are only of near-UV, while the outer phosphorescence is excited mostly by longer wavelengths...
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The double ended compact MH lamps with quartz outer, don't produce any dangerous short wave UV radiation, because like halogen lamps, their quartz outerbulbs are doped with materials that prevents the UV radiation to escape.
Compact quartz jacketed double ended and miniature 2-pin single ended MH lamps, require an enclosed fitting, only to contain the quartz pieces, should explosion would accur.
Their UV emission is similar to the screwbased MH lamps with glass envelope and the mercury lamps (Mainly long wave UV radiation).
Dor123, keep in mind that European and American standards are not necessarily similar. In North America, double-end MH lamps are made of quartz, so they need a shield to protect the surroundings both from UV radiations and eventual lamp rupture.
These rather low wattage lamps do not emit UV, as the quartz is doped (so unlike the burner), include north american market, the shield i necessary solely for explosion containment (an of course lamp protection).
I think UVC do not emit any of them, neither the high wattage ones, UVA and mainly UVB are supressed below the safe limit.
The blue radiating stuff on the outer (visible just after power ON) is the fluorescence of the UV absorbing doping, what when excited by the UV emit a bit of the blue radiation. Normal, UV transparent, quartz would not radiate in this blue...
Also, the glass used in non compact screwbased HID lamps isn't a borosilicate glass, but simply a hard-glass, since they shouldn't be exposed to the outdoor conditions, or the outerbulb will shatter (Thing that wouldn't accur if they would be made from a true borosilicate glass, which can withstand to thermal differences and willn't shatter because of this [The pyrex glass is from the borosilicate family]).
But usually the presence of the UV blocking feature is stated both on the lamp etch, as well as on the package.
The UV LED would not be reliable, as LED's are only of near-UV, while the outer phosphorescence is excited mostly by longer wavelengths...
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