Dennis,

Commercial forming gas is typically 5% hydrogen. It's used to
prevent/reduce light oxidation, but I never found it to be very
effective because of the inevitable mixing during the purge cycle. If I
remember right the explosive mixture limit is 8% hydrogen. There's also
an upper limit that I forget the value of where you're safe again, and
that's where hydrogen furnaces operate.

We used to crack ammonia to create a "pure" hydrogen atmosphere in the
hot zone for making hermetic glass seals. The conveyor portals were
blanketed with nitrogen. We had a few interruptions in the nitrogen that
automatically cut off the hydrogen, but you still get quite a boom out
of the residuals.

Andy Magee
Flex Guru
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