broken glass on my Mh fixture

[fencer]

Actually, that is partially true. If you go read that Osram document I posted on MH. You will find that the outer sleeve of DE's is a UV barrier. The glass that cracked is just protection for the bulb itself. It does filter out UV as well. If you blow out the bulb itself you can hurt yourself. As DE's work under hi pressure(70 psi) an explosion is possible an you get molten glass/metal flying at you. The glass has to be tempered