Opinions Wanted: "Techreational" Trimix Diving

[SailNaked]

Reg. sorry to derail your thread.

I love classes, I also like to learn new things and learn something for a purpose. I do not like having to take a class for no other reason other than it is in the way of my taking the class i really want to take. for instance some of the TDI instructors require a doubles course before you can take the Adv Nx/Deco course, some do not and it is not in the standards that I know of.

I am fairly certain that at some point in the deco course it could be pointed out that doubles are heavy and have 3 valves and what they do. it could be mentioned in passing that I should think about the weight differences and effects on buoyancy and wing requirements. and a sheet with the s-drills printed or better yet a discussion on them lasting no more than about 20 minutes would be sufficient(with homework to practice them). Do I really need a $300 separate course.

 

[netmage]

I have been diving a BP/w and long hose and have had good trim for the last 80 dives no course needed. I put on my doubles and went swimming, not much difference. I can hover at 12" off the bottom, turn, shoot an SMB and not stir up silt with doubles, no training other than youtube to show me what it was supposed to look like. splain me Lucy why I should pay $1200 for this course. I also read the free Navy manual and understand it.

I never said you did... If you look more closely at my previous posts, I was explaining how training has been structured, and more importantly how training progressions have had to change because people were not out gathering diving experience ...

I know many quality instructors that would not require an intro to tech course for someone proficient with the skills at that level...

I really need separate courses to know to read the labels on the bottles? or to follow my wetnotes on when to switch?

I need a course for all the theory and procedures on diving past 130 but it really does not change till I go past 190 and get into trimix.

If thats all you think it's about, then have at it... Oh, thats right, your in the middle of your IDC, you already think you know everything...

 

[SailNaked]

Point taken, I'll shut up now. I do not know what I do not know, and I am speaking hypothetically, in discussion.
I recently got off the phone yesterday a shop that has a "tech" course that does not certify you below 130 and does not teach deco, no He. for $1600. I know I am an ignorant DM but I will not be taking that course.

 

[netmage]

Where are you located - plenty of good recommendations across the country...

And plenty to avoid...

 

[Reg Braithwaite]

To clarify, the class I took addressed the use of mixes with a maximum PO2 of 1.4. I was calling that hyPERoxic because it was > 21%, like 25/25. My understanding is ghat hypoxic would only apply at much deeper depths, which would be outside that training by a long shot. Am I using the wong term?

 

[netmage]

To clarify, the class I took addressed the use of mixes with a maximum PO2 of 1.4. I was calling that hyPERoxic because it was > 21%, like 25/25. My understanding is that hypoxic would only apply at much deeper depths, which would be outside that training by a long shot. Am I using the wong term?

Hyperoxic > 21%
Normoxic = ~21%
Hypoxic < 18-21% depending on agency and which way the wind is blowing that day.

Hypoxic gases become a requirement in the > 200' realm...

Air/21% hits a 1.6 pO2 at 218'..... thus to dive deeper, you need something with less % O2...

At the surface, breathing a hypoxic mix - somewhere in the 16-18% range, you'll loose consciousness...

So, you would enter the water on one mix, maybe 32% nitrox, and switch to a bottom hypoxic mix in the 0-100' range on your way down.

 

[Wookie]

Somebody I respect told me the other day that helium mixtures of 20% or less should be treated as if it's air. I'm not too sure I buy it but there you have it. I know spearfishers that regularly dive to 200 feet, and add a little He to keep their PO2 below 1.4. They don't deco, they "wash the nitrogen out" with oxygen.

Helium is a tool, like a lead weight. You don't use a hammer when a lead weight will do just as well. If you're going to use the tool, I don't think that it is stupid to get some instruction in proper use of the tool. Helium is a fast gas. Ascent rates and deco times are much more critical using helium than air. YMMV.

Frank

 

[jorge.a.mahauad]

It is Advanced Diving for sure...

For me the main difference between rec and tec diving is the mindset of the diver. I personally think that for using trimix (even if it is normoxic) you need a tech diver mindset; so,

Why avoid proper training?

Personally I would prefer a 25 min dive with air up to 50 m and a proper accelerated decompression with 50% and 100% than a Trimix no deco dive at 130ft...

It would also be cheeper and more rewarding...

 

[Reg Braithwaite]

It is Advanced Diving for sure...

For me the main difference between rec and tec diving is the mindset of the diver. I personally think that for using trimix (even if it is normoxic) you need a tech diver mindset; so,

Why avoid proper training?

Personally I would prefer a 25 min dive with air up to 50 m and a proper accelerated decompression with 50% and 100% than a Trimix no deco dive at 130ft...

It would also be cheeper and more rewarding...

Well, don't forget that you are probably now talking about redundant back gas and deco bottles, along with all the failure modes they imply. So we are talking about quite a bit more training and expense. I may get there eventually but this seemed like a useful step at the time.

 

[Sloth]

I know spearfishers that regularly dive to 200 feet, and add a little He to keep their PO2 below 1.4. They don't deco, they "wash the nitrogen out" with oxygen.

what on earth does that mean? Are they going on 100% o2 at the surface with no in water deco?