Limitations of TDI helitrox?

[Wibble]

so carry two deco gasses for a 150 foot dive and do all the switches solo without verification all to avoid diving with a teammate...gotcha

Why do you need verification when you change gases? Don't you stop at the appropriate level and check whilst you switch? After all it's your life, so you have a lot of skin in that game.

If diving with multiple cylinders you need to be doubly certain you've pulled out the right reg, not to mention having the gas analysis tape on the neck of the cylinder to ensure it's the right one.

You don't need buddies to switch. You need yourself to ensure you've done your own checks.


Obvs. it depends where you dive. In mediocre visibility on a wreck you're pretty much diving alone for the whole dive including bagging off and decompressing. Ensuring that you've stopped at the right switchover point is a vital skill, just as is controlling your buoyancy so you don't drop below the MOD.

 

[flymolo]

You don't need buddies to switch. You need yourself to ensure you've done your own checks.

pretty sure every agency teaches buddy verification of switches

In mediocre visibility on a wreck you're pretty much diving alone for the whole dive including bagging off and decompressing

that's just an excuse people make when they don't have the ability to stick together.

 

[Wibble]

pretty sure every agency teaches buddy verification of switches

Yes, definitely.

However after a while there's more time decompressing alone. That may be outside of the agency's guidelines, but it's reality (for some)..

that's just an excuse people make when they don't have the ability to stick together.

I choose to mooch around on a wreck at my own pace. There may be other divers on it, but it's nice to be able to spend an hour on the wreck enjoying the flora, fauna and engineering, maybe routing around inside.

Then there's the relaxing hour decompressing alone. Just me and the bouncing reel a few feet away. It's almost zen-like relaxing time doing, as my wife doesn't believe me, nothing at all but breathing. Time passes surprisingly quickly.

I feel relaxed now...


Diving with others seems to add a great deal of stress to a dive as you always have to concentrate. Be that in a cave concentrating on passive signalling and following the leader/line whilst using the eyes in the back of your head for back-referencing and checking the person behind you is OK... Or being on a wreck with one eye out for the other person.

Some of us just like diving alone as we get more out of the dive.


Back on the boat though.. let the banter begin.

 

[Pearlman]

I don't understand the question. Handling multiple stage bottles greatly increases complexity and the risk of switching to the wrong gas. This isn't entry level. Regardless of agency, a diver should have significant experience with a single stage before taking a course that involves multiple stages. The GUE Tech 2 course covers this well so that would be one option for those who want to go that route.

Wrong choice of words on my part I guess - by “entry-level” I meant the minimum level of course that is expected to train a diver sufficiently for this task. My question has been answered though.

Thanks

 

[rjack321]

Genuine question - What course and agency would you say covers (or is the entry-level) with adequate/required training levels to handle multiple stage bottles?

Nobody should be teaching multiple deco gases and/or stages at the entry level. People need time in the water, repetition, and varied conditions to become genuinely adept at switches and a few days in a class isnt it.

Nowadays...
Entry level is 1 deco gas (normoxic)
Mid level is 2 deco gases or 1 deco gas plus a stage (normoxic)
Advanced is 2 deco gases plus stages (hypoxic)

Adding bottom stages to a 1 deco gas dive is "ok" if you are genuinely at the mid-level either via coursework or mentoring. A surprising number of people accidentally start the dive on their deco gas though - because they are flippant about gas switch protocols on the surface. UTD and GUE have both had this rough sequence for many many years. TDI and IANTD have had "flexible" standards which were intentionally vague because *reasons* and hence this question comes up because divers look to standards for guidance - even after the fact when their courses definitely didn't cover a topic. AN/DP for instance doesn't say you can't carry 2 deco gases so people sometimes do, even though their course didn't include 2 deco gases at all. Heliox doesn't definitely cover bottom stages either. So like in this case, TDI divers are left with uncertainty even self-assessing their skill set and what they should/shouldn't be doing because you don't know what you don't know

 

[flymolo]

Yes, definitely.

However after a while there's more time decompressing alone. That may be outside of the agency's guidelines, but it's reality (for some)..



I choose to mooch around on a wreck at my own pace. There may be other divers on it, but it's nice to be able to spend an hour on the wreck enjoying the flora, fauna and engineering, maybe routing around inside.

Then there's the relaxing hour decompressing alone. Just me and the bouncing reel a few feet away. It's almost zen-like relaxing time doing, as my wife doesn't believe me, nothing at all but breathing. Time passes surprisingly quickly.

I feel relaxed now...


Diving with others seems to add a great deal of stress to a dive as you always have to concentrate. Be that in a cave concentrating on passive signalling and following the leader/line whilst using the eyes in the back of your head for back-referencing and checking the person behind you is OK... Or being on a wreck with one eye out for the other person.

Some of us just like diving alone as we get more out of the dive.


Back on the boat though.. let the banter begin.

it's fine if you choose to do that, but i wouldn't be advocating for it or claiming it's the only way, or even a good way of doing things

 

[DiveLikeAMuppet]

It’s just a card, there is no scuba police. The line in the sand depends on your religion cult training philosophy.

I did OC ANDP and stuck to a single deco stage. Limiting dives based on lost gas/backgas deco was a nice limit. I later did normoxic with two deco gases once I was able to handle two stages and once I was comfortable with the amount of overhead it imposed. Even later I got a helitrox mod1 CCR card and obviously carried a deep bailout and a deco stage - which is explicitly prohibited by IANTD but possibly vaguely allowed by TDI.

So I definitely appreciated the flexibility. People might take helitrox as their first techie course, it’s intended for funny shops that might check a card to get you a little bit of helium (and a mortgage).

You can find strange lines in the sand with other agencies too - I think it’s bonkers to dive 18/45 to 51 meters with 30 minutes of deco with a single deco gas and hope for the best in poor viz, but that’s just me.

 

[flymolo]

It’s just a card, there is no scuba police. The line in the sand depends on your religion cult training philosophy.

I did OC ANDP and stuck to a single deco stage. Limiting dives based on lost gas/backgas deco was a nice limit. I later did normoxic with two deco gases once I was able to handle two stages and once I was comfortable with the amount of overhead it imposed. Even later I got a helitrox mod1 CCR card and obviously carried a deep bailout and a deco stage - which is explicitly prohibited by IANTD but possibly vaguely allowed by TDI.

So I definitely appreciated the flexibility. People might take helitrox as their first techie course, it’s intended for funny shops that might check a card to get you a little bit of helium (and a mortgage).

You can find strange lines in the sand with other agencies too - I think it’s bonkers to dive 18/45 to 51 meters with 30 minutes of deco with a single deco gas and hope for the best in poor viz, but that’s just me.

I don't understand backgas deco as a contingency when the classes are taught to a buddy team. you can share deco gas, can't you?

 

[Nick_Radov]

You can find strange lines in the sand with other agencies too - I think it’s bonkers to dive 18/45 to 51 meters with 30 minutes of deco with a single deco gas and hope for the best in poor viz, but that’s just me.

Which specific agencies are you referring to there? The one I am most familiar with trains divers to think rather than following arbitrary lines in the sand. Part of the dive planning process involves assessing environmental conditions and potentially limiting exposure if there is a high risk of team separation. You aren't required to push every dive to the limit of your certification.

 

[justinthedeeps]

Supposedly helium can embolize faster and is more dangerous on poorly executed ascents(?), also it is expensive and limited in supply, and is colder

Tough to blanket agree on or recommend 'excess' helium (or straight up heliox) for those reasons

Seems acceptable on CCR though, or some multi depth twinset outing when you might do a shallower dive in between deeper ones. Unless it is hypoxic..

Is helium's diffusion rate not actually riskier? Depends on what we believe about compartments and gas interactions?

N2 vs. He, what’s the difference? – The Theoretical Diver

thetheoreticaldiver.org