trimix training

[DCBC]

... I do not see the value in deep air as part of a mix class. Your threshhold for narcosis should have been addressed in a much earlier class, or during adv/nitrox-deco proc. what say you?

I agree with you Eric. diving DA and using Trimix are often separate programs. If the Agency makes certain recommendations or stipulates a DA requirement, obviously this must be followed. As I'm not aware of the specific requirements for instructing Trimix in all Agencies, I can't comment. DA is not a requirement for the Normoxic Trimix or Advanced Trimix program with the World Underwater Federation (CMAS).

Normoxic Trimix: Maximun recommended depth 60 Meters / 200 feet
Prerequisites: *** Diver (DM) or Advanced Nitrox, 150 dives plus 20 dives as an Advanced or Extended Range Nitrox Diver
Course Duration: 10 hours theory, 6 dives

Advanced Trimix (aka Trimix, Advanced Trimix, Sub-Normoxic Trimix): Maximum recommended depth: 100 Meters / 330 feet
Prerequisites: *** Diver (DM) or equivalent, Normoxic Trimix, 20 Normoxic Trimix dives (two within the last month).
Course Duration: 10 hours theory, 4 dives
(Note: Sub-Normoxic is defined as any Trimix diving gas mixture with an O2 content of less than 18%)

 

[waterpirate]

The deep air dives were/are not required for the agency, they were a part of a instructors spin on how to best get it done based on their experiances??? That is what I was questioning. Either you dive deep air or you do not. I failed to see then or in this thread a good solid justification for the 2 being combined in a normoxic course. I advocate the push for heliox as part of AN/DP.
Eric

 

[Dr. Lecter]

In your scenario, once I got the reg, wouldn't we begin our ascent? Or would you rather continue the dive?

My guess is that we would begin our ascent and be at the first deco stop around 100' in a few minutes making the narcosis minimal. This scenario hardly necessitates the need for deep air training.

Yes, because leaving a dive site is always as simple as just ascending.

 

[DCBC]

The deep air dives were/are not required for the agency, they were a part of a instructors spin on how to best get it done based on their experiances??? That is what I was questioning. Either you dive deep air or you do not. I failed to see then or in this thread a good solid justification for the 2 being combined in a normoxic course. I advocate the push for heliox as part of AN/DP.

I'm a strong supporter of diving DA for experienced divers who've trained for it. Many divers today just don't want to develop the skill-sets, so they just move on to Trimix. I suppose there're lots of people with disposable income to buy Helium...

Say you're using a Normoxic Trimix (Tx 20/40 for example) at 60 Meters (200 FSW). Your END is the same as breathing air at 32 Meters (105 FSW). Not something that would necessarily require deep air training. I think most divers doing Trimix training are usually pretty comfortable at 100 FSW on Air.

Definitions also matter. What is DA to you? Personally, I don't consider 100 FSW on air, DA...

 

[nimoh]

Yes, because leaving a dive site is always as simple as just ascending.

you win.

I should train on deep air just in case I am ever diving 18/45 at 200', get separated from my team, have a catastrophic failure losing all of my back gas, and run into a deep air diver deep inside a wreck with immediate ascent to a deco stop not an option.

 

[Adobo]

you win.

I should train on deep air just in case I am ever diving 18/45 at 200', get separated from my team, have a catastrophic failure losing all of my back gas, and run into a deep air diver deep inside a wreck with immediate ascent to a deco stop not an option.

I actually wouldn't mind getting more detail about this scenario.

I mean, it is true that you can't necessarily assume a direct ascent on a tech dive - even if it is a non penetration dive. For example, if the dive boat is anchored or tied to a mooring line, you might not have a choice but to get back to the upline before beginning your ascent. Even in the event of a catastrophic failure that leads to an out of gas scenario. Drifting while doing 20-30mins of deco in strong current might put you well beyond visual range of the crew of an anchored boat and perhaps have you reliving moments from the movie "Open Water".

For this reason, you might be diving 1/3s of your usable gas or even more conservative (UsableGas = StartPressure - MinGas). This should presumably allow you to get back to the upline even if you or your buddy goes out of gas at the furthest point away from the upline. And by the way, a reliable navigation aid will also be needed such as a reel. (Its not enough to dive 1/3s. You need to not get lost going back to the upline.)

The thing that is not clear to me is, why in this scenario would deep air experience be of benefit?

 

[nimoh]

I actually wouldn't mind getting more detail about this scenario.

I mean, it is true that you can't necessarily assume a direct ascent on a tech dive - even if it is a non penetration dive. For example, if the dive boat is anchored or tied to a mooring line, you might not have a choice but to get back to the upline before beginning your ascent. Even in the event of a catastrophic failure that leads to an out of gas scenario.


For this reason, you might be diving your usable gas as 1/3s or even more conservative. This should presumably allow you to get back to the upline even if you or your buddy goes out of gas at the furthest point away from the upline.

The thing that is not clear to me is, why in this scenario would deep air experience be of benefit?

Because when I go out of gas in this scenario, and the unknown deep air diver donates a reg, I would then become a deep air diver with no prior experience and subject to the increased narcosis without being able to ascend and mitigate the narcosis.

Perhaps it would also be prudent for me to get drunk tonight and practice calculating deco schedules on air, so that I would be able to recalculate my deco schedules doing half my dive on trimix and half on deep air while narc'ed, then check my answers in the morning.

 

[Dr. Lecter]

It's just amusing to me that I'm getting a 'that's just an unrealistic scenario' lecture from someone with an "Always plan for the rare things" quote in their profile, when the scenario I'm positing can and has happened to tech divers since before tech diving was a thing.

Maybe your team skills are so good, and your site selection and dive planning decisions are so exacting and risk-adverse that you yourself could never wind up OOG a ways from where you need to ascend, without one of your He-loving buddies in sight. Maybe you'd never conduct a penetration that required you to stage deco gas outside the wreck, which is a great way to find yourself needing to do navigation at the bottom before you get to just ascend. Maybe doing a few dives in the 150'-200' range on air would kill you rather than providing some useful perspective and another experiential tool in the toolbox.

Like I said, how you dive is not my concern. I just don't get people who obsess over a 'proper previous planning preventing piss-poor performance' approach to diving, but avoid with evangelical zeal the gaining of any experience with air below whatever (ever-climbing) ideal depth they've been told is unsafe without He.

 

[tkdgodess]

My take is how is how much helium do you need, how will you know if you haven't done a few deep air dives. What is acceptable end for me with he? 160 is my deepest on air, i remember every detail of my most recent. At least i have some perspective of my own personal end limits other than someone telling me. If your instructor is comfortable with you on air, and he dives air on a regular basis, why not learn under supervision?

add if you do the deep air, and are narced, why cant you signal to ascend to a shallower depth and finish your runtime? Getting narced isn't instant death. Oh i'm narced, lets ascend.... Noone has ever said no. You stay here.

 

[waterpirate]

My definition of DA in this discussion are the dives in the advert to the 200fsw range as part of mix training. Personaly what a person considers DA is all relative to: experiance on DA, work load, support, ect. I love to dive as shallow a END as makes sense to me. The deeper I go, I compensate by reducing work load and task loading. This thread has brought a lot of insight to the front, and information gained.
Eric