Original poster: "Steven Steele" <sbsteele@xxxxxxxxxxxxx>
Why would one have a spark gap in anything other than regular air?
Different gases have different breakdown, and more importantly, recovery
properties. The thermal and mechanical properties (primarily conductivity
and viscosity) also have an effect.
Hydrogen is very popular for fast gaps, because it "recovers" very quickly,
and has high thermal conductivity.
Electronegative gases (i.e. SF6) are used in high breakdown voltage
applications, but I don't know that they have particularly fast recovery.