Equivalent Air Depth question

[ginti]

Read somewhere that hydrogen does work (hydrolox) (sp?) but it has to have a very low oxygen content of less than 4%, circa 300m/1000ft.

hydrox -> hydrogen + oxygen -> link: Hydrox (breathing gas) - Wikipedia
hydreliox -> hydrogen + helium + oxygen -> link: Hydreliox - Wikipedia

These gases have been tested and used to reach the deepest equivalent depths ever (>700m) in hyperbaric chambers. But their use is limited to commercial diving, as far as I know; besides, they bring some others physiological problems.

On the other hand, I believe that heliox is relatively common for very deep (>90m) tech dives.

 

[Bob DBF]

And as we are here discussing the narcotic effect of N2 and O2, if one looks down the chart to CO2, it can be seen that there is another player in the game that muddies the waters further.

 

[tbone1004]

And as we are here discussing the narcotic effect of N2 and O2, if one looks down the chart to CO2, it can be seen that there is another player in the game that muddies the waters further.

most peoples experience of narcosis are likely caused by CO2. Most of the time if you dig into their experience further you'll find that they were working fairly hard when they experienced the narcosis which points to CO2 narcosis vs. N2 narcosis.

 

[ginti]

most peoples experience of narcosis are likely caused by CO2. Most of the time if you dig into their experience further you'll find that they were working fairly hard when they experienced the narcosis which points to CO2 narcosis vs. N2 narcosis.

And, correct me if I am wrong, CO2 narcosis is also related to stress, since (in theory) stress causes changes in breathing patterns which in turns lead to a high presence of CO2 in the bloodstream, do you confirm?

 

[Bob DBF]

most peoples experience of narcosis are likely caused by CO2. Most of the time if you dig into their experience further you'll find that they were working fairly hard when they experienced the narcosis which points to CO2 narcosis vs. N2 narcosis.

I would reword that to most people's experience of narcosis that they remember are likely caused by CO2.

Narcosis will not usually be noticed unless one is actively looking for it. It will be an unnoticed or pleasant experience, which without luck or intervention, can lead to one's untimely demise.

 

[Angelo Farina]

I would reword that to most people's experience of narcosis that they remember are likely caused by CO2.

Narcosis will not usually be noticed unless one is actively looking for it. It will be an unnoticed or pleasant experience, which without luck or intervention, can lead to one's untimely demise.

I was narched several times when young (and stupid). You understand easily if it was Nitrogen or CO2.
The first is really pleasant, the second is not, and leaves you with a bad headache...
My experience was that Nitrogen is typical of very deep dives in warm, crystal-clear water, no current, no stress, nice things to see. The second occurs at more limited depth (even less than 30m) in muddy, cold water, nothing nice to see, with current or heavy work to be carried on.
Of course also these environmental factors influence the "pleasantness" of narcosis...

 

[Akimbo]

Gas density certainly plays into the matrix. There is significant theory and very little consensus on the precise biochemical details behind biologically inert gas narcosis.

Just to add another data point to the discussion, Hydrogen is chosen as the diluent for saturation dives below about 500M/1,600', even though the relative narcotic potency is higher than for Helium. The work of breathing caused by increased gas density is the reason. As mentioned, CO2 is know to play a significant roll in NN (Nitrogen Narcosis) so gas density is an important factor, but not one that has been reduced to an equation.

 

[ginti]

Gas density certainly plays into the matrix. There is significant theory and very little consensus on the precise biochemical details behind biologically inert gas narcosis.

Just to add another data point to the discussion, Hydrogen is chosen as the diluent for saturation dives below about 500M/1,600', even though the relative narcotic potency is higher than for Helium. The work of breathing caused by increased gas density is the reason. As mentioned, CO2 is know to play a significant roll in NN (Nitrogen Narcosis) so gas density is an important factor, but not one that has been reduced to an equation.

As far as I understood, helium may cause HPNS. I believe hydrogen doesn't (or at least causes fewer symptoms).

We are a bit deeper than the original idea of the OP

 

[ScubaBadger32]

You narcosis will most likely be worse using nitrox as you extend your bottom time, if you believe O2 to be equally narcotic.

just want to make sure i understand, the narc depth is gonna be the same (if not worse) when diving nitrox. To fix it, you gotta dive trimix right?

 

[ginti]

just want to make sure i understand, the narc depth is gonna be the same (if not worse) when diving nitrox. To fix it, you gotta dive trimix right?

Yes.

His statement was not about the narcotic power, but about the time that you will spend at depth. If you dive recreationally, you are more likely to avoid decompression and, even if you do some deco (like CMAS/BSAC recreational divers do), it is probably short. Often, rec divers use nitrox to extend the duration of the dive (at depth). The more time you spend at depth, the more you are likely to experience narcosis.

Personally, I am not sure of how time affects narcosis; for sure the physiological mechanisms require a bit of time to happen, I just do not know how much. If @mac64 said that you are more likely, probably the required time to experience the symptoms is important...