TDI Advaced Nitrox and Deco Procedures

[jagfish]

Hi Andy
Always good to notch it up to the next level. Good on ya!

Jim

 

[PerroneFord]

what depth ranges are those classes teaching for? in the 130-170 foot range, 50% has a lot of advantages over just taking 100%. Taking two deco gases has the significant downside of the risk of breathing the wrong one, and doesn't speed up your deco much.

Adv. Nitrox ends at 130ft for IANTD. Beyond that is Extended Range (which is a deep air course). Agreed getting onto your deco at 50% has some significant advantages over waiting to get to 20ft.

You might find that 50% nitrox is plenty. If you do longer shallow dives (say 60 min at 100 feet), then maybe 100% has some benefits.

What kind of benefits are you talking about? Actually, I think carrying oxygen ALWAYS has some benefits, but not always in terms of decreasing deco time, versus the risk of making a potentially lethal gas switch at depth.

doing 150 feet dives on air seems a bit odd as helium can really help with the narcosis and isn't any harder to dive than air etc.

The training agencies seem to still push helium training DEEP into the education process. However, we are starting to see recreational trimix classes at some of the more forward thinking ones. I know GUE does it, I think IANTD has a recreational trimix class. Anyone know of any other agencies?

Also, if I was doing serious cave diving at 100 feet, I'd be really tempted to take 30/30 . Having a clear head in a cave sounds like a pretty good thing to me.

30/30 seems like a good mix for a lot of "shallow" diving. I think the risk is that you REALLY do have to have some solid buoyancy control on helium. Although mine isn't bad now, I'd still wait another half a year or more before taking a rec. trimix class.

 

[ianr33]

38% and 91%?

R

91% is used by divers that have bouyancy control that is more than good enough for 80% but not yet good enough for 100%

 

[Soggy]

The training agencies seem to still push helium training DEEP into the education process. However, we are starting to see recreational trimix classes at some of the more forward thinking ones. I know GUE does it, I think IANTD has a recreational trimix class. Anyone know of any other agencies?

NAUI Tech has helitrox (26/17 to 150') and heliair (can't remember the mix, but it is to 180'). They use kind of strange mixes, but there are no limitations explicitly stated on the card. Both can be combined with adv nitrox/deco procedures so you don't have to do 150' dives on air.

 

[PerroneFord]

That sounds pretty good Soggy. I may have to look into those next year when I'm ready.

 

[Soggy]

FWIW, Helitrox can also be taken on its own as a purely recreational class as well. Not sure where you are located, but chickdiver (Heather C) and runawaylobster (Lesley J) are both NAUI Tech instructors in Florida.

 

[H2Andy]

How long did the course go for and how much did it cost?
Im looking at doing the same courses and here its 6 evening of theory & confined water diving @ 3 hours each and 6 open water dives. Cost is $795 NZ About $550US.

that sounds like a very comprehensive course.

both Advanced Nitrox and Deco Procedures, combined, cost $400 (we got the
"old" price of $300, but just in the nick of time).

one classroom session. no pool dives. we did 3 dives for Adv. Nitrox, and 4 dives for
Deco Proc. (7 together), spread over 4 days (two weekends).

I went to 55msw on air as part of my TDI extended range course and suffered mightily from the effects of narcosis, made worse by poor vis and current.

well, thankfully we didn't have any current. it was pitch black, and there were
all sorts of particulates and silt and what not floating around, so vis wasn't
particularly good (but i hear it gets a lot worse). the low vis was a new thing
for me. i am used to the clear vis of the caves (most of the time, anyway).

38% and 91%?

yeah, with 21% backgas. we used what we had available, and planned
the dives accordingly.

91% is used by divers that have bouyancy control that is more than good enough for 80% but not yet good enough for 100%

them's fighting words

 

[PerroneFord]

FWIW, Helitrox can also be taken on its own as a purely recreational class as well. Not sure where you are located, but chickdiver (Heather C) and runawaylobster (Lesley J) are both NAUI Tech instructors in Florida.

My normal instructor is a NAUI course director. He's 30 minutes away, so its very convenient. Heather is only a few hours away as well.

 

[limeyx]

Adv. Nitrox ends at 130ft for IANTD. Beyond that is Extended Range (which is a deep air course). Agreed getting onto your deco at 50% has some significant advantages over waiting to get to 20ft.



What kind of benefits are you talking about? Actually, I think carrying oxygen ALWAYS has some benefits, but not always in terms of decreasing deco time, versus the risk of making a potentially lethal gas switch at depth.



The training agencies seem to still push helium training DEEP into the education process. However, we are starting to see recreational trimix classes at some of the more forward thinking ones. I know GUE does it, I think IANTD has a recreational trimix class. Anyone know of any other agencies?



30/30 seems like a good mix for a lot of "shallow" diving. I think the risk is that you REALLY do have to have some solid buoyancy control on helium. Although mine isn't bad now, I'd still wait another half a year or more before taking a rec. trimix class.

Well, the cases you have are:

1) Just bring 50%. Benefits: You start your deco deeper, and your minimum gas requirements are low because you only need gas to get 2 divers to 70 feet.
2) Just bring 100%. Minimum gas gets really large as you now have to get 2 divers to 20 feet, and planning for a loss of deco bottle means more gas needed. Also, if you believe that bubble growth can be a problem, you are allowing bubbles to grow more than if you do deep(er) stops.
3) Bring both. For that range, I think you might (might) save 5 mins deco, versus the complexities of breathing the O2 deep and toxing, versus the complexity of switching between two deco mixes and the extra planning complexity.

Just doesn't really seem worth it.

The 100% O2 on longer shallower dives (instead of 50%) can be useful as due to the extended bottom time, you are filling up your slow tissues more (as far as I understand it), whereas for shorter deeper bottom times, the big problem is off-gassing the faster compartments (hence the 50% switch).

I have a friend here doing the NAUI (or TDI) course I think and they use 26/17 for 150 as well. I think the difference between 21/35 (which I would use) is that there is still a "discussion" about whether O2 is narcotic or not. For the few $ extra in He costs, I think I'd rather assume that it is (as well as the other potential benefits of He)

 

[limeyx]

...
30/30 seems like a good mix for a lot of "shallow" diving. I think the risk is that you REALLY do have to have some solid buoyancy control on helium. Although mine isn't bad now, I'd still wait another half a year or more before taking a rec. trimix class.

Not sure why you'd need any better buoyancy control than doing a 100 foot (or so) dive on 32% really. You dont want to do a fast ascent in either case.

If you can hit 1 min stops at 50,40,30,20,10 feet then shouldn't be an issue.
Of course, there are other issues planning significant dives at that depth (gas planning, handling emergencies, teamwork etc.) which are critically important.