triox vs. trimix?

[graham_hk]

Originally Posted by rossh

Hi Rod,

You might want to consider comparing some plans before you swap over.


HMS Victoria sample plan, 120m 5 mins - 96 Runtime in Decochek, 94 mins in VPM-B +2
Mohammad's 220m Dive Plan on Decochek, is approx equal to same plan with VPM-B +2.

It would appear that the AB model of Decochek and VPM-B can align rather well over 100m.

(Note If you try these compares - take care to align descent, ascent rates and actual bottom times in each - any variance in these will make a big difference.)

Come on Ross you'll have to do better than that - two profiles!

[Mark Powell]

Originally Posted by Brian of Aquanauts

Going through my TDI Instructor manual all I can find for deco gas requirements is "Cylinder volume appropriate for planned dive and student gas consumption". So TDI leave this to the instructor, do IANTD recommend your reserve amount?

Section 8.9 of the TDI Instructor Manual. For Decompression Mix Cylinders the cylinder should contain a minimum of 1.5 times the gas required for the decompression.

[Mark Powell]

Originally Posted by Brian of Aquanauts

But you have to dive narked in up to 45m while you get experience with ADV Nitrox & Deco before Trimix.

If this were possible as a first course then i'd agree, but to be inexperienced, and off your box is a bit of a messy combination.

I know lots of people get put off when they have their first CO2 hit, triox at the start would help with that issue.

Brian you should know better than that.

You DO NOT need to dive to 45m to get experience with Adv Nitrox and Deco before Trimix. The course standards clearly state that one of the qualifying dives needs to be deeper than 30m, but that can be 31 or 32m. Once qualified, If the diver really doesn't want to dive below 30m then they can then get experience in the 25m-30m range before going on to Trimix. If even a single 32m dive is more than they are willing to accept then they can combine Advance Nitrox, Deco Procedures and Trimix into a single course so that they never need to dive below 30m on anything other than Trimix. It's a long intensive course but is perfectly accetable under TDI standards (sort of sounds a bit like a Tech 1 course).

One of the advantages of TDI is that it offers the flexibility to follow either path.

[Mark Powell]

Originally Posted by Brian of Aquanauts

you must have 25 dives deeper than 30m as a prereq to TDI Trimix

Ian's Triox course is a combine adv. Nitrox and triox course so yes it is a first tech course and suitable to do before entry trimix.

However the GUE route will give you a bit more in terms of dive skill IMHO

Nope, for TDI Trimix you need at least 100 dives, no specification on depth but you must have Adv Nitrox and Deco (or combine the courses).

For TDI Advanced Trimix you do need at least 25 dives deeper then 30m.

[nickb]

Originally Posted by Mark Powell

Brian you should know better than that.

You DO NOT need to dive to 45m to get experience with Adv Nitrox and Deco before Trimix. The course standards clearly state that one of the qualifying dives needs to be deeper than 30m, but that can be 31 or 32m. Once qualified, If the diver really doesn't want to dive below 30m then they can then get experience in the 25m-30m range before going on to Trimix. If even a single 32m dive is more than they are willing to accept then they can combine Advance Nitrox, Deco Procedures and Trimix into a single course so that they never need to dive below 30m on anything other than Trimix. It's a long intensive course but is perfectly accetable under TDI standards (sort of sounds a bit like a Tech 1 course).

One of the advantages of TDI is that it offers the flexibility to follow either path.

This is exactly what I did. I took AN&DP in 2004 and spent 18 months diving with deco gas in the 25-35m range before taking the Entry Trimix course. The deepest I dived was 42m on the Markgraf with Tricky and neither of us was too happy about it. That was what prompted us booking the trimix course as soon as we got back from Scapa.

[big_si]

Originally Posted by Mark Powell

For TDI Advanced Trimix you do need at least 25 dives deeper then 30m.

Bit of an aside to the OP...

Wow! 30m? Seems odd to 'allow' people to dive to 'just' 30m and then go "in at the deep end" (pun intended!) to qualify to 100m.

[weazelz]

Originally Posted by big_si

Bit of an aside to the OP...

bit late for that now Si

[Mark Powell]

Originally Posted by big_si

Bit of an aside to the OP...

Wow! 30m? Seems odd to 'allow' people to dive to 'just' 30m and then go "in at the deep end" (pun intended!) to qualify to 100m.

There is also the prerequisite that they must also be either Entry Level Trimix or ERD qualified.

[Rod Abbotson]

Planning very deep dives on heleox or rich trimix I found the difference between the GF deco and the VPM deco to be pretty extreme. If i dived a lot in this range (100m+) id start wil VPMBE level 4 and see how it felt before venturing any where near VPMB.

Great thanks for the advice I'll use level 4 and vpmb/e and see how that goes.

Basically been using Buhlmman for years with no probs so agree with a lot of divers on the issue, v planner I find easy to use and teach and the later versions seem to be getting better, I always run my plans through several deco software options to see what comes out, there is usually not that much difference! If common sense is used!


On another point on the whole shallow diving with helium triox mixes - I eventually got around to reading last years BSAC Incident reoport - seems to be a few problems there with divers having buoyancy problems and not sticking to the deco schedule properly resulting in trips to the chamber where on air they would probably have been ok. Food for thought!

Rod

[divingniknaks]

Originally Posted by Rod Abbotson

- seems to be a few problems there with divers having buoyancy problems and not sticking to the deco schedule properly resulting in trips to the chamber where on air they would probably have been ok. Food for thought!

Yes, do Fundies !

Sorry, couldn't resist given some recent threads