Partial Pressures limit...

[SDAnderson]

I would think that since Hydrogen is highly reactive with Oxygen, you'd have a byproduct of water... or does this only occur in the presence of a catalyst... How does HydrOx affect the diving? I've never heard of it. I'm basically trying to figure out how an elements weight or reactivity affects its breathability. Have there been any mixes tried of O2 with a air compound like CO2 (I know that this would give the diver one hell of a headache, but y'know what I'm askin')...

- PV

Combining hydrogen and oxygen produces dihydrogen monoxide and a whole lot of energy. BOOM! Kind of makes narcosis issues irrelevant.

Somebody has tried mixing everything with oxygen for diving, including krypton. Heck, some of these folks are even on this board. If you're really interested, get yourself a copy of the NOAA diving manual for a brief introduction to other inert gases.

 

[Don Burke]

I would think that since Hydrogen is highly reactive with Oxygen, you'd have a byproduct of water... or does this only occur in the presence of a catalyst... How does HydrOx affect the diving? I've never heard of it. I'm basically trying to figure out how an elements weight or reactivity affects its breathability. Have there been any mixes tried of O2 with a air compound like CO2 (I know that this would give the diver one hell of a headache, but y'know what I'm askin')...

- PV

The upper explosive limit for hydrogen is something like 94% (can't find the book right now). You'd end up with a bottle with a maximum operating depth and a minimum operating depth of about one hundred feet. That would also mean a transition bottle of heliox to take a few breaths from both on the way up and the way down to purge oxygen on the way down and hydrogen on the way up.

Hydrogen is more narcotic than it's density would suggest. It is often used in pretty small amounts along with helium in very deep mixes.

 

[DepartureDiver]

Argon is extreemly narcotic and is really nasty for deco, far worse than N2. You don't want argon in your breathing mix!

YES! Argon is very narcotic. I also have to disagree that neon is better than helium. Yes neon is less soluble than N2 and it is much less narcotic, but the experiments are lacking ... and as another post stated ... VERY expensive. I thought about it for awhile and in addition to not wanting to be a complete lab rat, it was about $800 for about 200 cubic feet.

 

[Drew Sailbum]

Generically, the lighter the molecular weight, the less work of breathing you will encounter. This becomes something of a consideration at significantly deep depths. Replacing some of the nitrogen with helium not only reduces the narcotic effect of the gas, but also lowers the work of breathing for these deeper dives.

But this should not be taken to extremes. At deeper technical depths, HPNS (High Pressure Nervous Syndrome) becomes an issue in Heliox mixtures. The solution is to mix back in a bit of nitrogen.

 

[eod]

I'm in a Nitrox course right now and we're learning about PPO and how the dive tables are created from these numbers. I know that this is the limiting factor in diving, but I'm wondering what is the maximum partial pressure of nitrogen is.
- PV

N2 is toxic above somthing like 11 ata. Of course this has no practical meaning in diving, but if you expose yourself to such an environment you probably will get unconsious from the N2.