TDI XR to TDI Trimix Crossover?

[Rybee]

Am looking to dive the Blue Hole Arch in Dahab, bit of a bucket list dive for me that I want to finally tick off. I am TDI XR certified to 55m on Air so the dive is possible… just.

However I’d prefer to do it on Trimix for two reasons:
1) 55m leaves about 1m tolerance and not much wiggle room as the arch is around ~54m (I believe)
2) Narcy Narc Narc. 55m on air is pretty grim… the arch is a notorious dive and I’d rather be doing it with a clearer head / lower END using Trimix.

I’ve compared the course specs and the skills look the same? I understand the theory will differ but the practical in water skills seem identical? No mask ascent, tox diver, breath hold swim, gas switching, diver tow, catastrophic gas loss etc etc…

Is it possible to crossover from XR cert to Trimix cert without paying for the entire course and completing (essentially) the same course as before? I’m obviously more than happy to pay for some training dives and learn the theory etc but I’d feel a tad short changed if I had to repeat all of the same skills again?

Am I missing something, is it possible, any advice & tips?

Thanks,

 

[VikingDives]

You should have had to repeat those skills when you went from AN/DP to XR too. IIRC, the eLearning is the same for XR and Trimix, so you shouldn't have to pay for that.

 

[Omisson]

No it is NOT possible to do so. You MUST be on Trimix for all 4 dives for the Trimix certification, whereas Extended Range ONLY uses Air, Nitrox, and Oxygen as breathing media. There is no credit across these two courses offered by TDI since 2018.

Here are the course requirements:

Extended Range
1. Four dives with a minimum accumulated bottom time of 100 minutes
2. All dives must be deeper than 30 metres / 100 feet with 2 dives deeper than 40 metres / 130 feet
3. A maximum of 2 dives from Advanced Wreck course may be credited towards the total dives required, at the instructor’s discretion

Trimix
1. Four decompression dives using trimix as bottom gas are required with a minimum accumulated bottom time of 100 minutes
2. Two of the dives should be deeper than 40 metres / 130 feet.
3. A maximum of 2 dives from the Advanced Wreck course may be credited towards the total dives required, at the instructor’s discretion

Hope this helps.

 

[Rybee]

No it is NOT possible to do so. You MUST be on Trimix for all 4 dives for the Trimix certification, whereas Extended Range ONLY uses Air, Nitrox, and Oxygen as breathing media. There is no credit across these two courses offered by TDI since 2018.

Here are the course requirements:

Extended Range
1. Four dives with a minimum accumulated bottom time of 100 minutes
2. All dives must be deeper than 30 metres / 100 feet with 2 dives deeper than 40 metres / 130 feet
3. A maximum of 2 dives from Advanced Wreck course may be credited towards the total dives required, at the instructor’s discretion

Trimix
1. Four decompression dives using trimix as bottom gas are required with a minimum accumulated bottom time of 100 minutes
2. Two of the dives should be deeper than 40 metres / 130 feet.
3. A maximum of 2 dives from the Advanced Wreck course may be credited towards the total dives required, at the instructor’s discretion

Hope this helps

No it is NOT possible to do so. You MUST be on Trimix for all 4 dives for the Trimix certification, whereas Extended Range ONLY uses Air, Nitrox, and Oxygen as breathing media. There is no credit across these two courses offered by TDI since 2018.

Here are the course requirements:

Extended Range
1. Four dives with a minimum accumulated bottom time of 100 minutes
2. All dives must be deeper than 30 metres / 100 feet with 2 dives deeper than 40 metres / 130 feet
3. A maximum of 2 dives from Advanced Wreck course may be credited towards the total dives required, at the instructor’s discretion

Trimix
1. Four decompression dives using trimix as bottom gas are required with a minimum accumulated bottom time of 100 minutes
2. Two of the dives should be deeper than 40 metres / 130 feet.
3. A maximum of 2 dives from the Advanced Wreck course may be credited towards the total dives required, at the instructor’s discretion

Hope this helps.

Though frustrating to hear yes it does help.

I guess I’ll have to pay the full course fee again and repeat the same skills albeit on different gas.

Cheers TDI

 

[Josh the diver]

Though frustrating to hear yes it does help.

I guess I’ll have to pay the full course fee again and repeat the same skills albeit on different gas.

Cheers TDI

technically you can take advanced trimix with just TDI extended range based on prerequisite standards.

 

[Omisson]

You should have had to repeat those skills when you went from AN/DP to XR too. IIRC, the eLearning is the same for XR and Trimix, so you shouldn't have to pay for that.

He could just sign up for Advanced Trimix since there is a prerequisite of either XR or Tmx...

​

Advanced Trimix:​

• Minimum age 18
• Minimum certification of TDI Extended Range or Trimix Diver or equivalent
• Show proof of 100 logged dives, 25 must be deeper than 30metres/100feet

 

[Whitrzac]

He could just sign up for Advanced Trimix since there is a prerequisite of either XR or Tmx...

​

Advanced Trimix:​

• Minimum age 18
• Minimum certification of TDI Extended Range or Trimix Diver or equivalent
• Show proof of 100 logged dives, 25 must be deeper than 30metres/100feet

I'm curious if any instructor would actually allow it...

Going from breathing air for everything to hypoxic is quite a jump

 

[Omisson]

Im

I'm curious if any instructor would actually allow it...

Going from breathing air for everything to hypoxic is quite a jump

Going from a deep extended range, stage decompression certification to hypoxic trimix is a big jump? How so?

Maybe you just don't understand the requirements for Extended Range (which is after Advanced Nitrox and Decompression Procedures).

Is it a Stage/Deco or Gas Volume issue?

Extended Range Diver: This course provides training and experience required to competently utilize air for dives up to 55 metres / 180 feet that requires staged decompression, utilizing nitrox mixtures or oxygen during decompression.

Trimix Diver: Utilizes breathing media where the oxygen concentration is at least 18 percent (up to 21%) which can be used as deep as 60 m/200 ft (at 18%) without exceeding a PO2 of 1.4 ATA, that requires staged decompression, utilizing nitrox mixtures or oxygen during decompression.

Air has a 1.4 ppO2 limit - thus equating to a 56.6m/185ft maximum depth when breathing Air (21% O2).
Normoxic Trimix has a60m/200ft limit at 18% and 187 feet at 21% with a ppO2 limit of 1.4ATA.

185 feet versus 200 feet.... not really a difference. So gas volumes, deco requirements, and depths are virtually identical - what differs is gas costs and the variability of run times... which vary based on those mixes.

So....no issue there.

So maybe it is a Skills Gap issue?

Extended Range Performance Requirements

....Demonstrate competence managing 2 stage cylinders, either 2 deco gas or 1 deco and extra bottom gas, including drop and recovery while maintaining position in the water column. Demonstrate ability to confirm gas switches at depth with buddy/team members....TDI Standards and Procedures Part 2: TDI Diver Standards Version 0123 814.

Trimix Diver Performance Requirements
...Demonstrate competence managing 2 stage cylinders, either 2 deco gas or 1 deco and 1 extra bottom gas, including drop and recovery while maintaining position in the water column3. Demonstrate ability to confirm gas switches at depth with buddy/team members TDI Standards and Procedures Part 2: TDI Diver Standards Version 0123 814.

No problem on the skills side either...

Counter diffusion maybe? of course, only when a drysuit is in use and most XR instructors I know already recommend a separate inflation bottle for drysuit regardless of breathing media at depth to avoid depletion.....and argon is a better insulator anyway.

So, nope, counter diffusion isn't an issue....

So while I'll grant that helium is a fast gas and your stop depths must be more strictly maintained, what exactly (beyond the impacts on run time and gas costs) are exactly the differences that would prevent, or deter an in-standards jump from Extended Range to Advanced Trimix.?

My question is what would cause someone to say they're "curious if any instructor would actually allow it..."
since its an in-standards, same skills jump, between Trimix and Extended range?


Dive safe,

Dan-O

 

[Miyaru]

Interesting plan. Yes, it is probably possible to make shortcuts, join a normoxic trimix course and do the Arch on your last course dive.

You will lack the experience you would have gained from the longer route.
And a characteristic of technical diving: no shortcuts.

The Arch is not a short stretch. How easy will it be to breathe at 55m, with overhead, while finning that distance with all your tanks? Read: gas density and CO2 retention.

Before the arch, dive the Canyon. And then do the Canyon plus the deeper part below the exit on normoxic. Log some hours.
Slow progress results in more solid experience than shortcuts ever could.

 

[divezonescuba]

I would think that any skills deficiencies would be addressed during dive 1 of the advanced trimix course and additional dives prescribed as necessary.

In the hypoxic trimix courses that I have taught in Dahab we initially dive at the lighthouse up to 165 ft and then make several progressively deeper dives at the blue hole.

The canyon is a great dive, but it is substantially different than the blue hole as the bottom is always just a few feet below you once you get inside the crack.