MH bulb has inner and outer glass bulb

> From: Stephen.Pushak at hcsd_hac.com
> When I talked to the guy who made up my last MH setup, I told him
> about the potential hazards of exploding MH bulbs and UV radiation
> released. 

When they explode, they probably cease emitting UV.  Oh sure, there
may be a microsecond or two where they are both emitting AND
exploding, but I would worry less about the UV and more about the
zillions of rather hot glass fragments being flung about.

> He said: they don't explode when they burn out and he's
> seen tons of burnt out ones. 

We replace ours after 12 months which is long before the rated
MTTE (Mean Time to Explosion). 

> He also remarked that the safety glass on the lamp fixture is not
> usually present since the bulbs are actually two bulbs, a small one
> about 1.5" and the larger enclosure. Presumably the large bulb
> contains fragments in case the little guy bursts. Any comments?

Perhaps the outer bulb would contain stuff if the inner bulb LEAKED, 
but I would suspect that if the inner bulb exploded, it would take the
outer bulb with it, glass being rather fragile and all that.  I think
the outer bulb is just there as a UV filter.  Hopefully, the acrylic
"splash guard" on the bottom of our fixtures would contain or at
least slow down the hot glass fragments if an explosion should occur. 

Have any users of MH bulbs ever seen one "explode"?