Partial Pressures limit...

[PolsVoice]

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.

Also we're learning abourt Heliox and how He and Ne are less soluble in the body and thus are used for deeper dives. I'm assuming that this is because of the inertness of the Noble gasses, But does the atomic weight of the element play into how soluble the gas is? If so, what about other 02/other gas mixes, like NeOx, or more likely ArgOx? Argon is already used for drysuits so it seems that this would be easy to experiment with and Neon is so prevelent in lightbulbs that I would think that it would be too hard to get the gas. Problems with gas prices aside, have any of these been tried?

- PV

 

[Northeastwrecks]

As far as I know, exposure to high partial pressures of Nitrogen will not put you into convulsions. Instead, problems arise because the Nitrogen becomes increasingly narcotic.

There is a concept called Equivalent Narcotic Depth (END) in which the narcotic effect of a particular gas calculated off the PPN2 of the mix. The agency I train with (GUE) recommends that the END be kept below 100. To do this, the diver replaces the Nitrogen with Helium, which is much less narcotic.

People have tried NeOx, ArgonOx and HydrOx. Other then being incredibly expensive, I don't recall what happened with NeOx. I believe that some entities, including the French military, have done some very deep dives with HydrOx. ArgonOx is extremely narcotic.

There are some threads on this issue in the archives. Its also come up on other sites (see below). You'll find more information if you do a search.

Good Luck

 

[chrpai]

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.

Oh here we go again, another deep air debate. What your really asking is what is the MND ( Maximum Narcotic Depth ) in terms of Equivilant Narcotic Depth.

Some people say 80' some say 100' some say 130' some say 150', 160', 200' you get the idea.

If you were to breath air using generally recognized limits of 130' then you would be diving a max PN2 of 3.85.

 

[Northeastwrecks]

Oh here we go again, another deep air debate. What your really asking is what is the MND ( Maximum Narcotic Depth ) in terms of Equivilant Narcotic Depth.

Some people say 80' some say 100' some say 130' some say 150', 160', 200' you get the idea.

If you were to breath air using generally recognized limits of 130' then you would be diving a max PN2 of 3.85.

Mr. Painter is correct when he states that different agencies teach different END's.

Chris, what END do you stick to when diving Helium based mixes?

 

[Spectre]

As far as I know, exposure to high partial pressures of Nitrogen will not put you into convulsions. Instead, problems arise because the Nitrogen becomes increasingly narcotic.

Techically I believe that nitrogen does have a toxic level... but that level is far beyond anything that you could experience on air, O2 comes into play far before. I guess it could be a concern if you cut your O2 content by adding nitrogen... but that'd be kinda dumb But for all practical purposes, O2 will be a concern far before nitrogen is.

Neon is definately a better choice then helium, as is hydrogen [I believe], but the former is prohibitively expensive, and the latter... well.. you think o2 cleaning is important?!

The dive tables weren't created based on the PpO2 content, but I believe they were considered in defining what a recreational depth limit would be, as 130' is just about PpO2 of 1.0.

 

[chrpai]

Mr. Painter is correct when he states that different agencies teach different END's.

Chris, what END do you stick to when diving Helium based mixes?

I don't dive helium, and I err on the side of conservatism when considering whether oxygen is narcotic or not. All things considered including narcosis, I choose not to dive past 100'. Since you mentioned your agency being GUE, you might find it interesting that this is one of their teachings that I agree with.

 

[Northeastwrecks]

Neon is definately a better choice then helium, as is hydrogen [I believe], but the former is prohibitively expensive, and the latter... well.. you think o2 cleaning is important?!

My neighbors have asked me why the gas supply truck drops bottles off at my house. They were somewhat reassured when I told them that the bottles werehelium and O2.

If I were to start diving HydrOx, I cannot imagine what they would think when I put the No Smoking signs up on the sidewalk.

 

[PolsVoice]

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

 

[pipedope]

Works at depth because there is not enough O2 in the mix to support combustion. This is only useful at depths far beyond anything recreational divers are likely to go to.

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

O2 is always the big problem, both too much and too little can kill you.

 

[MikeFerrara]

My neighbors have asked me why the gas supply truck drops bottles off at my house. They were somewhat reassured when I told them that the bottles werehelium and O2.

If I were to start diving HydrOx, I cannot imagine what they would think when I put the No Smoking signs up on the sidewalk.

Your neighbors?

The police wanted to know why I had all the gas.