TDI Extended Range & Helitrox

[scadreau]

It is just the analogy of keep using 21% O2 and as much Helium as the pocket can afford, that makes you go near the Trimix dept, don't fully understand the limitations to be set Helitrox to limit you to 45m and 20% He, only thing I can see is that they are trying to go in baby steps towards trimix, but by the other hand they allow you to 55m on air, what is the problem to go, 55m on 21% O2 and 20%He, I don't know if you guys understand what I'm trying to point out.

Because the Helitrox course was designed to be in line with the Deco Proc course just adding a splash of helium. So the same depth limits apply. The 20% limit applies because it really does not affect your decompression, where the richer helium mixes can increase your deco obligation. Also, at 20%, the risk of IBCD is significantly less even if switching to a fairly weak nitrox.

 

[tomfcrist]

Because the Helitrox course was designed to be in line with the Deco Proc course just adding a splash of helium. So the same depth limits apply. The 20% limit applies because it really does not affect your decompression, where the richer helium mixes can increase your deco obligation. Also, at 20%, the risk of IBCD is significantly less even if switching to a fairly weak nitrox.

Scott,
I agree with you for the most part. The Helitrox course is designed to introduce divers to helium. More recent research has called into question the "Helium Penalty" as far as deco obligation is concerned.

Remy,
The Extended range course is fine if you don't mind a little bit of narcosis. If your internal risk acceptance level doesn't allow for being narced, go straight to trimix. There are a lot of folks that still dive regularly to 170-180' on air. I think that's more a reflection of the price of helium than anything else....but even the cheap bastards will spend the money on helium if they are going deeper than that. If helium is too big an expense, don't go so deep. Many of us also have our own accounts with gas supply companies and get our helium fairly cheap(in comparison to paying the markup at a dive shop).....I think I pay $135 for a T bottle.

 

[rongoodman]

That is the recommendation of my instructor as well, once I finish AN/DP to continue to Helitrox

You do understand that you can combine Helitrox with your AN/DP course? There's no need to wait and do it as a separate course, and you'll have the advantage of a clearer head while learning all the AN/DP skills.

 

[DA Aquamaster]

As noted above, just do AN/DP or Helitrox (same basic class, it just uses 20% helium in the mix), then do the trimix class.

The ER class requires 4 dives and certifies you to 180'. The trimix class also requires 4 dives and certifies you to 200'. The extra cost of the helium in the mix is a small fraction of the total class, gas, and boat costs.

 

[stuartv]

If the OP finishes AN/DP without Helitrox, why bother to go on and take Helitrox later? DP certifies for depth to 150' and Helitrox is the same. It doesn't certify you to go any deeper.

I mean, if you've finished DP and want more, why not just go straight on to TDI Trimix? Does the Trimix course cost a lot more than a standalone Helitrox course?

My AN/DP instructor said he would add on Helitrox training and cert for a very small extra cost, so I am planning to do that. But, if it were going to be a full-on standalone course, it seems like it would make sense to skip it and just take Trimix.

 

[WarrenZ]

Thats my plan once I get comfortable with 150 I am going to go after Trimix.

 

[toby43]

What are the opinions from the experts about TDI extended range?

My instructor is not fan of this course, he has the opinion that any Tec diver venturing beyond 30m shall use some helium in his mix, keeping the boundaries on O2 exposure of course.

As per TDI it mention about 55m range for air, and the Helitrox down to 45m with 20He in the mix, the concept of Extended Range is the use of Air as your gas and the training go around this, but by looking at Trimix were this trains the diver on 18%O2 and down to 60m, it seems that the Extended Range can be combined with the Helitrox, but there is no combination like this suggested by TDI, any particular reason for this ?

I was in exactly the same position as you a few years back and asking the same question about ER. My opinion is that if you do TDI ER and then TMX course together it gives you a nice slow build up from 45m handling one stage, to 60m handling two stages and saves you a shed load of helium cost along the way. Half my TMX course cost was helium. The caveat to that is that conditions were benign; warm, clear water no current (Dahab). I am glad that I dived air to 55m with an instructor for the purposes of the course. It was valuable experience. Would I do it again? No, now probably 45m END max in the same conditions.

 

[Michael Guerrero]

I guess it's been said why they structure the course that way. I would just do AN/DP and then Trimix. Do some dives with multiple deco bottles before Trimix though.

 

[lerpy]

I completed the Deco/Adv Nx with Helitrox in August. All the advice I was given is this is a good way to go, and when I looked into it and did some thinking I agreed. Deco/Adv Nitrox certs you to 150, for me being able to add in that bit of helium to increase the safety and decrease the narcotic affect is worth it. I feel like going to 150 on air would reduce my safety, simply in the form of the clarity of my thinking and actions, especially if something went south. I ultimately only did a couple of dives with the helium, but I was amazed at how clear I was, and how good I felt after the dive. I have dove to 120 on air a couple of times, and I certainly did not feel as clear and comfortable as I did with a bit of helium offsetting the nitrogen.

I think it is a good idea, and then it allows you to do some deep dives getting experience, with that added safety margin, before moving onto a trimix course. JMHO

 

[kensuf]

I feel like going to 150 on air would reduce my safety, simply in the form of the clarity of my thinking and actions, especially if something went south.

And statistics would back this up. In 1996 I was in charge of analyzing accidents for the NACD and I took a look at deep cave diving deaths for trained cave divers. Remember, this was back before trimix was the norm and deep air was still quit the accepted practice.

I took a look at all cave diving fatalities of trained cave divers between 1965 and 1994, in total, we were talking about 51 fatalities. I expected the majority were deeper than 200', but it turned out only 1/3rd were. The majority, a whopping 62% of them, were between 130' and 180'. Turns out that many were at about 150', it seems when your mental acuity is slowed down, and things start going "pear shaped," one problem can lead to another, and then another, and you get a nice mess that can snowball out of control quickly.