Deep Diving on Nitrox question

[mainedvr]

Your choice of gas is your decision, not the group's decision.

If you wanted to use air instead of Nitrox, then you should have done so, no one can tell you otherwise.

Do not let other people dictate your choice of gas or drive profile, that's your responsibility.

And anyone who recommends EAN32 at 130 feet is someone who I would avoid.

I totally agree, what if you were not nitrox certified, was that a condition of the dive. If your an experienced diver (no you personally just generally) you know what works for you and your limitations. If its the dive ops policy for that certain dive well then again a choice the diver needs to make. When I did some wreck diving in NC most dives were in the 120' range and the OP provided 30%, they had a few folks diving air, they just recommended Nitrox.

 

[Storker]

At 40m on a nitrox mix, ie no helium, your gas density will be significant and tending towards reducing the effectiveness of your breathing and especially your ability to get rid of CO2

In the the presentation posted in vey interesting article by simon mitchell there are some interesting data (scroll to 46:30 to see them). Those data strongly indicate that a gas density of ~6 g/L or higher carries a significantly increased risk of excessive CO2 retention. Air and recreational nitrox mixes reach a density of 6 g/L at a depth between 35 and 37m (about 120').

I'm quite wary of narcosis and have set my personal depth limit at ~30m. This is another very good reason for me to avoid deeper diving (as I'm not trimix certified).

 

[Lorenzoid]

I expressed my desire to make that dive on AIR at the Aldora office the night before. Next morning the boat to "Devil's Throat",left without my gear on board. Aldora had switched me to another boat going somewhere else. This was my final dive day on Coz so I missed out on "Devil's Throat" on that trip.

That's good to know. So instead of sounding like a wuss and telling them I'm not comfortable doing Devil's Throat, I can tell them my personal PPO2 max is 1.2 or something like that, and if the mix in my tank isn't suitable I'm not going to do the dive. Eh, never mind. Being a wuss is fine with me.

 

[k4kafka]

That's good to know. So instead of sounding like a wuss and telling them I'm not comfortable doing Devil's Throat, I can tell them my personal PPO2 max is 1.2 or something like that, and if the mix in my tank isn't suitable I'm not going to do the dive. Eh, never mind. Being a wuss is fine with me.

Well, Lorenzoid...the bottom line was,I didn't get to do "Devil's Thoat" that trip because Aldora took me off the boat rather that provide a tank of AIR for that deep dive. Of course,I would have been the only diver in the group using a different mix on that first dive,so I guess,...in their mind,that was unacceptable.

 

[scubadada]

I still find the EAN32 cylinder difficult to accept. Perhaps @Dave Dillehay will clarify Aldora's policy.

 

[uncfnp]

I probably should not jump in here since I have only dove Cozumel/Aldora once but since I am a bit of a special needs diver here is my understanding of Aldora and their diving "norm."

Typical diving on nitrox with Aldora will be 32 first and deepest then 36 for next shallower dive. These are the standard mixes that is readily available from their fill shop. Other mixes are available but not readily. It takes a special request to get a personalized mix such as 28 or 30. Or even O2.

As to an air option, Aldora tries to match divers. And as a nitrox diver I appreciate that since Aldora also wants all divers to dive as a group. So an air diver on a nitrox boat may mean all the other divers must end their dive early. So I understand why you were placed on a different boat. But I also understand why you were upset.

You asked for personal opinions and practices. I was taught 1.4 to 1.6. My instructor for the course encouraged us to make an informaed risk assessment then decide for ourselves. And adjust as conditions dictated. His typical was 1.5 and that has been my choice for years as well so I probably have a higher acceptance of greater PPO2 exposures for brief periods then the average SB'er.

Would I have done the dive on 32? If it was a dive I wanted. Yes. But that choice is made with a fairly good knowledge base of the risk and alternatives. And also knowing that ultimately the dive is in my hands and I will abort or change the profile as my needs dictate.

 

[drrich2]

As to an air option, Aldora tries to match divers. And as a nitrox diver I appreciate that since Aldora also wants all divers to dive as a group. So an air diver on a nitrox boat may mean all the other divers must end their dive early.

I recall in an older thread contrasting Aldora with another dive op., it was indicated that Aldora has the whole group ascend together at the end of the dive (the other op. sent people up in buddy pairs, for example, as their gas pressure ran low; which practice is more desirable was a point of some debate).

Is this still the case?

Richard.

 

[Lorenzoid]

I recall in an older thread contrasting Aldora with another dive op., it was indicated that Aldora has the whole group ascend together at the end of the dive (the other op. sent people up in buddy pairs, for example, as their gas pressure ran low; which practice is more desirable was a point of some debate).

Is this still the case?

Richard.

I can't speak for anyone else, and I have only dived once so far with Aldora, but I know my wife and I ascended when we reached our limits, and others ascended a bit later.

 

[uncfnp]

I recall in an older thread contrasting Aldora with another dive op., it was indicated that Aldora has the whole group ascend together at the end of the dive (the other op. sent people up in buddy pairs, for example, as their gas pressure ran low; which practice is more desirable was a point of some debate).

Is this still the case?

Richard.

I think it may vary a bit by the DM. The one we dove with most absolutely would not let us ascend individually even though we have extensive experience with drift dives. I was told by another individual that was the general Aldora policy. But I also got the impression from another Aldora DM that he had some discretion regarding this.

 

[scubadada]

With Aldora, my son and I never dived with a group larger than 4 . We were well matched, always ascended together with the DM at the end of the dive. First dive air, 2nd dive EAN32, average dive duration 75 minutes. This included Devil's Throat, Cathedral, and Barracuda