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Regarding the use of neon, I can't see the advantage of using neon for deep 
diving. Apart from the lack of narcotic effect at moderate depths, it would 
have to be to dense to breath at depths over about 100mtrs. Even at 100mtrs, 
pure neon is equivelent to breathing air at about 70mtrs. Most people who I've 
heard talking about neon tell me it's MUCH easier to breath than nitrogen, 
almost the same as helium. (one of these people is currently writing a 
rebreather training course... scary stuff.)

Add to this slow offgassing (cf helium), and you have a gas which is harder to 
treat than a helium bend. And as Richard Pyle correctly stated, it offers only 
small savings in deco time over a properly selected trimix, and adds to deco 
for short dives if used as a replacement for nitrogen. 


Richard Pyle wrote:

>H2 has some serious risks associated with it; particularly >the fact that
>it combusts in the presence of more than 4% O2 (evidenced >by the
>Hindenburg disaster).  Thus, it can't really be breathed >safely at depths
>less than about 130 feet.

Is Hydrogen spontaniously combustable with the presence of >4% oxygen, or does 
in behave like normal substances that require an ignition to complete the fire 
triange? Is the flashpoint temperature with >4% oxygen very low?

Lastly, has anyone read any work done on a and b values for hydrogen, and if so 
is the ceiling for a hydrogen sat dive at a shallower depth than an equivelent 
helium sat dive?  

Thanks, Rod Nairne. 

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