Why do you need training for normoxic trimix?

[rjack321]

I’ve actually seen the results. I like to get off helium quite deep, like 130 feet onto 32%, and 80% at 15 feet. I watched my buddy go blank for an entire stop. She switched to rebreather shortly after.

That's a narcotic slam, IBCD would (in theory) be an in-water DCS hit which doesn't seem to happen at reasonable ENDs (130ft being deeper than average but still reasonable)

 

[Gareth J]

There are two elements to Trimix training, one of which is the theory related to using Helium in the breathing mix. But the second, and probably the most important, is the incident management, and the planning required to mitigate risk and manage failures during a trimix dive.
When I switched from OC to CCR, although, having a full OC trimix ticket, I opted to do the rebreather trimix course. Whilst there was the usual planning and dive skills, the most arduous, and most interesting, where the incident exercise and drills.
Granted, this was well beyond the limitations of Normoxic trimix.

Also having spent time with students on Trimix courses, and prior to that ERD, I have been surprised by the number of divers who attend who are diving well outside their comfort/capability zone. On occasion, it can be quite frightening.
I have a huge amount of respect for those instructors who run these courses, I don't think I would have the nerve to have that level of responsibility with unknown divers under these circumstances. When i have taught advanced courses, I have had the advantage of knowing the candidates in advance, or I have been an assisting instructor.

 

[Superlyte27]

I’ve actually seen the results. I like to get off helium quite deep, like 130 feet onto 32%, and 80% at 15 feet. I watched my buddy go blank for an entire stop. She switched to rebreather shortly after.

Agree. I've seen it. But not at 200'. More like 400'. It's real, but I don't know a single person diving technically or recreationally that's been affected by it.

That's not to say that a Normoxic class doesn't need to be taught. I think it does. But I'm not certain that ART, Normoxic AND Hypoxic all need to be taught. It's very redundant. The planning and math don't change. Sure, there's some issues like IP Pressure that is more of a problem at 400' than 200'.

 

[Superlyte27]

There are two elements to Trimix training, one of which is the theory related to using Helium in the breathing mix. But the second, and probably the most important, is the incident management, and the planning required to mitigate risk and manage failures during a trimix dive.
When I switched from OC to CCR, although, having a full OC trimix ticket, I opted to do the rebreather trimix course. Whilst there was the usual planning and dive skills, the most arduous, and most interesting, where the incident exercise and drills.
Granted, this was well beyond the limitations of Normoxic trimix.

Also having spent time with students on Trimix courses, and prior to that ERD, I have been surprised by the number of divers who attend who are diving well outside their comfort/capability zone. On occasion, it can be quite frightening.
I have a huge amount of respect for those instructors who run these courses, I don't think I would have the nerve to have that level of responsibility with unknown divers under these circumstances. When i have taught advanced courses, I have had the advantage of knowing the candidates in advance, or I have been an assisting instructor.

I agree with this too. I've shared with some of you my story about the time a student completely shut down at about 160' after returning from about 200'. He completely blanked out to everything for 8 solid minutes. He had no idea, didn't remember any of it, and didn't start to regain composure until I had brought him to 90'. Better to understand that with someone there, trained in the ability to save you, than to do it by accident with another diver who isn't prepared or expecting it.

 

[tbone1004]

@Superlyte27 and IP only an issue with certain regulators when you get down that deep *i.e. sealed diaphragms that are over-compensating*. I still have yet to understand why normoxic is a mandatory prereq for hypoxic, especially on the CCR side of things

 

[Superlyte27]

If your regulator is putting out 90psi on 300' dive, you have an issue. Part of my pre dive safety checks is making sure IP is right.

Believe it or not, IP at 90-125psi is very common a few months after a rebuild. Not sure who you guys got rebuilding this stuff, but I see it nearly every class.

 

[Merlino]

[QUOTE="Gareth J, post: 8644024, member: 468596] the second, and probably the most important, is the incident management, and the planning required to mitigate risk and manage failures during a trimix dive.[/quote]

That’s interesting, do you mean specifically related to the helium or more to the overall “you’re going deeper and you will likely incur a deco obligation so any incident will need to be solved underwater”

I have a huge amount of respect for those instructors who run these courses, I don't think I would have the nerve to have that level of responsibility with unknown divers under these circumstances.

For sure!

 

[Gareth J]

[QUOTE="Gareth J, post: 8644024, member: 468596] the second, and probably the most important, is the incident management, and the planning required to mitigate risk and manage failures during a trimix dive.

That’s interesting, do you mean specifically related to the helium or more to the overall “you’re going deeper and you will likely incur a deco obligation so any incident will need to be solved underwater”



For sure![/QUOTE]

A bit worried by the statement "will likely incur a deco obligation", if you are doing dives that require Helium, you are doing dives that WILL incur a deco obligation. The NST is so short otherwise its not worth getting in the water ... or spending that much money on the gas.

As a minimum you are wearing a twinset, and at least one stage. You have a level of task loading because of the equipment, well beyond what in the US is classified as recreational diving, and you should be following a pretty precise dive plan. Computers have reduced some of the time issues, that hard table diving imposed, but this type of diving is about precision.

Minor problems at depth escalate rapidly. What in shallow water is a minor inconvenience, can be life threatening when deep.

 

[Superlyte27]

I had three friends in Diepolder. They were all wearing the same 6 computers when all 6 shut down 20 minutes into the dive at over 280'

Luckily, the guide had made this dive 100 times before and was able to remember his deco profile enough to surface. Yikes!

 

[Merlino]

A bit worried by the statement "will likely incur a deco obligation", if you are doing dives that require Helium, you are doing dives that WILL incur a deco obligation. The NST is so short otherwise its not worth getting in the water ... or spending that much money on the gas.

No need, I have zero intention of diving helium without getting proper training as stated in my first post. I’m just genuinely curious.

Personally, I’m more interested in getting cave trained and I could see the merit in diving e.g. 30/30 in caved for the clearheadedness it brings.

As a minimum you are wearing a twinset, and at least one stage. You have a level of task loading because of the equipment, well beyond what in the US is classified as recreational diving, and you should be following a pretty precise dive plan. Computers have reduced some of the time issues, that hard table diving imposed, but this type of diving is about precision.

Minor problems at depth escalate rapidly. What in shallow water is a minor inconvenience, can be life threatening when deep.

Thanks, that makes sense.