Should TDI Helitrox replace AN+DP?

[Jeremy Williams]

There are no straight answers. Helitrox is clearly better from a safety perspective. If that was all that matters then nobody would teach or dive on air below 100ft/30m or so. If only it were as simple as just that.

The cost of helium is annoying. The (lack of) availability of Helium is a problem.

 

[CAPTAIN SINBAD]

People seem to have a love and hate relationship with TDI-Helitrox. The theory is the same as Trimix except it comes with a depth limit. After taking Helitrox when you take Trimix, you are really not learning much except management of two deco bottles? It may seem like a way to milk the customer twice. Furthermore, since Narcosis varies so much from person to person, 150' depth range may enable a person to realize their own personal limits as to when you should have Helium in your tank.

 

[RyanT]

After taking Helitrox when you take Trimix, you are really not learning much except management of two deco bottles? It may seem like a way to milk the customer twice.

Not having taken the helitrox course, I don't really know what it entails skills-wise, so maybe I'm off base here. For my own trimix course, however, my instructor provided a lot of emphasis on task loading. It went far beyond just managing two deco bottles. He had us rotate bottles, share air, manage a lost gas scenario in the team, manage a lost mask diver, recover an unconscious diver, and we often had to manage many of these tasks simultaneously in a ripping current. If helitrox covers these kinds of task loading skills then yes, trimix would be a minor stepping stone. If not, the the trimix course represents a step up in the skills development needed for diving deeper.

 

[CAPTAIN SINBAD]

Just got off the phone with a Helium supplier. "Helium is becoming a rare commodity. A lot of balloon business are shutting down. We no longer have it and we do not know when we will have it or at what price."

 

[rjack321]

People seem to have a love and hate relationship with TDI-Helitrox. The theory is the same as Trimix except it comes with a depth limit. After taking Helitrox when you take Trimix, you are really not learning much except management of two deco bottles? It may seem like a way to milk the customer twice. Furthermore, since Narcosis varies so much from person to person, 150' depth range may enable a person to realize their own personal limits as to when you should have Helium in your tank.

So shocker here...
There's almost nothing to "learn" to breathe normoxic helium. You just breathe.

Not killing yourself with your deco gas? That's the important part. The "milking" as you say - keeps your skills in tune with your risks

 

[CAPTAIN SINBAD]

So shocker here...
There's almost nothing to "learn" to breathe normoxic helium. You just breathe.

Not killing yourself with your deco gas? That's the important part. The "milking" as you say - keeps your skills in tune with your risks

I was presenting the perspective of old school TDI instructors. The logic behind TDI AN-DP (150ft) and Trimix (150-200) used to be that since Narcosis is subjective and varies drastically from person to person, the entry level ANDP course would enable students to recognize the limits of their own impairment and how it effects them independently. Recreational deep divers are already doing 130ft dives so this course does not add much depth to it. It gives them bottom time. Some instructors still feel that 150 on air is not enough for a lot pf people to realize the limits of their impairment. They take their students deeper during their Trimix training.

While introducing his Trimix class, John Chatterton writes the following:

My Basic Trimix Diver Training Course meets all of the standards for the TDI Normoxic Trimix certification, however I integrate what I feel are the core elements of the TDI Extended Range course into this training as well. IMHO, there are important lessons to be learned by diving air to deeper depths (around 180'), prior to assuming the additional responsibilities of deeper dives on more complex gas mixes. Students who successfully complete this training should be able to competently plan and conduct decompression dives on Air or Normoxic Trimix, up to a depth of 200 fsw.

This particular philosophy of approaching Helium is in sharp contrast to what I have studied in UTD courses. Modern research seems to give us new reasons why Helium should be used for dives deeper than 100.

 

[rhwestfall]

The unpredictability of response to depth is a key element. I've been stupid at 110' at times, and other times it all seems well. It surprises me as to what I don't remember seeing when we go over camera footage I have taken on various wrecks.

He was something I had hoped to implement....

 

[CAPTAIN SINBAD]

I have dive buddies who become irritable and irrational at 115' but they do not believe that they are narced. I also have dive buddies who operate DSLR camera on manual mode at 150 with perfect and varying shutter speeds and aperture settings. If the goal was to create an efficient dive team then it makes perfect sense to standardize Helium below 100.' Even if you happen to be one of those who can manage Narcosis, why would you want to be with a dive buddy who is not fully up there?

 

[rddvet]

Wasting helium by using it in open circuit diving should be banned along with the clowns wasting it in balloons.

Wrong answer try again.

Do me a favor and go dive Ginnie on air or 32%. Then do the same dive on something like 30/30 or 21/35 and let me know how different the cave looks. I work in Largo and live in St Pete and have a booster and a compressor. I'll even fill your tanks for you for free (if you have an appropriate cert) so we can see how the experiment goes. The first time my wife dove Ginnie with helium creeped her out. It was a totally different cave and she was shocked at how much she hadn't seen. Even for me and her that rarely get narced, the difference was and is eye opening.

 

[DiveTucson]

This is interesting to me for sure and with the recent studies, my MOD3 CCR class, and the death of a close friend (mix was a factor but not the main cause. Had he not been narc’d out of his mind he may have survived the other events) I personally as a diver have changed the way I dive.

I will not dive an END much over 100’ any more depending on conditions. Local site is a dark cold lake. Tropics are a little different. So as an instructor how can I teach AN/DP or equivalent if I don’t believe in diving that way?

I have moved all my entry level tech courses to include Helitrox or Trimix depending on the agency I am running my course through. I know it’s not the only way and there are pros and cons to each but I believe in teaching the way I dive.

And as I point of reference I am TDI Extended range certified and have many dives on air in 170-185’ range. Never again...