What age for tech?

[DCBC]

Does your mixed gas instructor cert convey magical mind reading powers?

When I asked if you were a mixed-gas Instructor, I was not being facetious. I was trying to understand on what you were basing your opinion on.

An Instructor's ability to read a student is essential. It's not a matter of reading minds; the onus is on the student to convince the Instructor that s/he does indeed appreciate the risks they are about to take. If not, they don't dive.

SB has a recreational focus, and the OP is asking about what age for Recreational Tech diving...The OP didn't ask about commercial diving...How is it useful to discuss training the op is not seeking?

It's the same. Any particular gas does not affect an Accountant any different than it does a Salesperson. Gas absorption doesn't show partiality to occupation. It affects a recreational diver exactly the same way as it affects a commercial diver.

Perhaps you can explain: "Why is it necessary for a diver who is certified to dive to 180 feet, to take a separate course so he can dive to a maximum of 196 feet?" It doesn't matter what the person's occupation is. Why?

 

[AndyNZ]

Wow! There are times when the time difference between NZ and the US really makes a difference.....!

DCBC - my post, which included the TDI depth limits for there courses, was really intended to provide the OP with an idea of what exactly is involved in reaching an Advanced Trimix certification, not as any means of justifying the standards, or limits.

Personally, I think the risks involved in 100m dives way exceed the experience of any diver who just started technical diving "recently". Again, personal opinion, I think it's unethical of any instructor to train even an experienced recreational diver from Advanced Nitrox through to Advanced Trimix in a few weeks.

To put it in to context, going down is easy.... coming up is hard. I did my TDI Advanced Nitrox & Decompression Procedures course about 3 or 4 years. Ignoring what the standards say, this is a "moderate deco course involving air/nitrox as backgas, with a single decompression mix". I naively thought that I was a "technical diver" and could cope with technical dives.

A few years ago, I took a GUE Fundamentals course - it seemed a backwards step, but it was a useful eye opener. The others on the course were fairly experienced, so we get stretched beyond the minimum skills required. The skill combination that really opened my eyes to how woefully under-prepared I was for the dives I was doing was simply doing a simulated deco ascent, whilst sharing backgas and deploying an SMB as a team. The aim was to hit every stop as per the simulated deco schedule - we screwed it up, none of us on the course had ever done anything like this before.... yet it is an entirely realistic scenario. Add in having to do a gas switch, or a lost mask into that - it's hard.

Even 50m is a serious proposition. A fcuk up at 50m is not a routine exercise - dealing with the problem(s) whilst hitting your deco stops, performing your gas switch, switching to the right gas and so on adds a great deal of task loading. Quite frankly, someone who has just done a few dives in that depth range is going to struggle with that - it's experience that counts, not oxygen tolerance.

The margin for screwing up an ascent from 100m, when you've only got twenty or thirty dives in a twinset is huge.

There is, and I say this with sadness (as a TDI instructor myself), a huge variability in TDI instructors. I've seen TDI instructors who don't teach to check the MOD of your deco mix before switching to it. I've seen TDI instructors who not only don't teach, but simply aren't aware of the potential failures of a manifold setup. If you get one of these who offers to teach through to Advanced Trimix in a few weeks.... and you walk away thinking you are "qualified" to dive to 100m, the potential for dying at some point after that is fairly high.

 

[AndyNZ]

Perhaps you can explain: "Why is it necessary for a diver who is certified to dive to 180 feet, to take a separate course so he can dive to a maximum of 196 feet?" It doesn't matter what the person's occupation is. Why?

I'll have a bash at this.

I'm guessing that you are really asking about the difference between the Extended Range and Normoxic Trimix courses, given the depth limits you've given.

The TDI courses are, IMHO, structured to provide a gradual introduction of skills. I don't teach ER or NT, but can give you an idea of what is involved in the courses leading up to these.

Advanced Nitrox is a strange course, quite frankly it only really exists as a separate course any more because dealing with 100% O2 is a requirement for CCR divers. Realistically, for OC, it is bundled into Decompression Procedures.

DP is an entry level tech course, which is essentially restricted to a single deco gas. The depth limit associated with this course is a *training limit*. It's there essentially to limit the deco obligation to something that is realistically achievable with a single deco gas.

Extended Range and Normoxic Trimix are "equivalent" in many ways. Both introduce a second deco gas/travel gas, and have essentially the same skills involved. The difference in depth limit comes from the different gasses use. ER is "deep air" programme, and a 55m depth limit (for training) is there as a means of limiting the ppN2. NT allows gases with fO2 between 18% and 21%, the deeper limit is there to reflect the ability to change the equivalent narcotic depth, whilst still controlling the max ppO2 on the dive.

You don't need to do both ER and NT - either is consider a prerequisite for TDI Advanced Trimix. It's the ability to juggle two deco/stage bottles that is really needed. My personal opinion is that ER is a bit dated as a programme, it's there for people who want to do deep air.

Hope this helps clear things up a bit.


EDIT: Realised that I didn't really answer the question! If you have a diver who has done the ER course, the reason they would have to do the NT course to "be qualified" to dive to 60m is that there is no coverage of trimix in the ER course. But they could not do the ER, and just do NT. There is nothing to stop an ER diver doing 60m dives on air if they so choose - the 55m limit is a training limit, and a recommendation for ongoing diving. There is no "TDI police" to enforce it. Personally, 60m on air scares the willies out of me - a ppN2 of 5.5ATM is serious. It's someone's personal decision as to whether they want to do it, but they'd be narc'd off their t1ts and it's a dive I wouldn't choose to do.

 

[DCBC]

DCBC - my post, which included the TDI depth limits for there courses, was really intended to provide the OP with an idea of what exactly is involved in reaching an Advanced Trimix certification, not as any means of justifying the standards, or limits.

Thanks Andy. As I mentioned, the non-technical diving standards (as far as I'm concerned) have really taken a dump over the years. There seems to be an attitude among many recreational divers to go mixed-gas early. Do your air and nitrox courses at or near the same time. It goes from there...

I suppose what I'm not getting here is that I certify someone to dive to 200 feet on mixed gas, s/he has been given all the tools to do a 300 foot dive. The right mixture(s) are straight forward to plan and task loading is not a problem. If it was, they wouldn't be certified to 200 feet in the first place.

This is a personal perspective, from what I have seen in the Navy and commercial areas (not a recreational perspective). I'm aware that a recreational diver's training is less intensive, but I couldn't see myself dropping what was necessary for any recreational diver who just wanted to make a 300 ft dive on the weekend.

For me each step in the training process would produce the desired result. As I've mentioned, the only difference as far as the diver is concerned is the equipment to be used, not the competence of the diver at depth.

My comments regarding oxygen tolerance and fitness are, in my opinion, key mixed-gas training prerequisites.

 

[cool_hardware52]

When I asked if you were a mixed-gas Instructor, I was not being facetious. I was trying to understand on what you were basing your opinion on.

An Instructor's ability to read a student is essential. It's not a matter of reading minds; the onus is on the student to convince the Instructor that s/he does indeed appreciate the risks they are about to take. If not, they don't dive.

So every body you ever "passed" had as complete an understand of the risk involved on the day you passed them as they did a year or two later or 50-100 dives later?

If you think that apparently experience is of *Zero* value.

It's the same. Any particular gas does not affect an Accountant any different than it does a Salesperson. Gas absorption doesn't show partiality to occupation. It affects a recreational diver exactly the same way as it affects a commercial diver.

When did I say the philology was any different between recreational and commercial divers?

Perhaps you can explain: "Why is it necessary for a diver who is certified to dive to 180 feet, to take a separate course so he can dive to a maximum of 196 feet?" It doesn't matter what the person's occupation is. Why?

What is the real difference to the diver by using a Trimix 20/35 to 200 ft, Trimix 10/40 to 300 ft or Trimix 5 in Helium to 1500 feet? Is a whole course necessary to teach someone to use a traveler? I don't get it.

Perhaps you can explain why you can't maintain a coherent consistent position in these threads.

First you argue that's there is no difference between a 200 ft dive and one to 1500 ft and now you want to compare two dives that differ in depth by ~1/2 ata.

It's really pointless to even bother to engage you.

Sadly instead of adding to conversation, and I'm sure you could, your need to flaunt your resume and massage your ego results in this off topic nonsense.

Tobin

 

[DCBC]

If you think that apparently experience is of *Zero* value.

The diver is safe when they are certified; experience isn't needed to be gained to insure safety or competence. It is however a valuable commodity that they will gain over time.

Sadly instead of adding to conversation, and I'm sure you could, your need to flaunt your resume and massage your ego results in this off topic nonsense.

I don't need to impress anyone Tobin, and really don't give a dam what you think.

 

[ucfdiver]

I don't need to impress anyone Tobin, and really don't give a dam what you think.

Your posts don't relay that.

Tobin,

You should look at this guys comments in the cave diving section, I'm guessing you'll just give up the argument. When you try to debate, you get the "I'm a cavern instructor" response....if you want to see what a joke this is, check the recreational agencies requirements to teach cavern, you'll be shocked

 

[cool_hardware52]

The diver is safe when they are certified; experience isn't needed to be gained to insure safety or competence. It is however a valuable commodity that they will gain over time.

What exactly does "experience" add if not increased safety and competence?

I don't need to impress anyone

Your user name,

DCBC

Your Signature,

ACUC ITE283EA
NAUI Course Director 4728
PADI MSDT 3941
CMAS M3CDN080
IDEA IT-1662
DCBC/IMCA Mixed Gas / Commercial Instructor

and your manner argues otherwise.

Tobin

 

[AndyNZ]

For me each step in the training process would produce the desired result. As I've mentioned, the only difference as far as the diver is concerned is the equipment to be used, not the competence of the diver at depth.

I think the two are related.

For example, the DSAT Tec Deep course (as was, it's now broken up) introduces two stage/deco bottles from the beginning and immediate results in divers certified to 55m. It's equivalent to TDI Deco Procedures and Extended Range.

The learning curve is very steep. Not only are you expected to be able to learn to manipulate the valves on your twinset, and identify and resolve failures, but there's also dealing with two deco tanks, with the associated skills of gas switching.

The TDI approach isn't perfect, but essentially it's a way of controlling that task loading. So learn about the twinset and gain competence in that. Whilst you are doing that, keep you depths moderate. Add in a single deco mix, learn how to do a gas switch correctly with a single tank. Once you can do that, add in a second tank and apply the same gas switch protocols.

You are correct, the outcomes are the same - but the learning process is different. I would much rather break the learning into logical, consistent steps because it makes the learning more constructive. The depth is irrelevant, it's the competence and slickness that comes with experience. The depth is about "you haven't got the skills/equipment/experience yet".

Personally, I rather like the GUE standards that mandate a particular number of dives between courses. It gives some confidence that the "raw input" to your training process is more likely to be able to be transformed into the desired output.

 

[AndyNZ]

Lighten up, guys!!!