Limitations of TDI helitrox?

[Wibble]

Opinion, not fact.

The world is replete with examples of highly skilled individuals coming together to accomplish more as a team.

I don’t sense anybody’s asserting that team diving is the only way and that anybody who doesn’t choose it is _________ (insert negative adjective).

But it does seem like you keep asserting that people who choose team diving are negligent or unskilled. Perhaps that’s your experience but I don’t think projecting it on every other corner of the world holds any water.

It’s a favorite song you like to play but it doesn’t seem anybody’s tuning in.

I need to restate the point I made as I didn't make a good enough job of explaining it...

Of course working with others is better for achieving goals. Many hands make light work; many brains make better decisions, etc., etc.

Diving is very much like that. Except when it's not; you're on your own, lost your buddies, mired with a problem. Then you have to sort things out for yourself. If you're used to someone checking you over before jumping in, you'd naturally become less attentive because someone else helps out. OK, you may have a team that "fines" you or mercilessly takes the piss because of some small issue -- that drysuit hose -- but most of the time people will just point it out and even connect it for you. Kind of they give you a fish to eat, not let you fish for it yourself.

If you don't have that reliance; you make doubly certain that you've done those checks because... you are the only one doing it.

Similarly if you've a problem underwater you have to deal with it. This will teach you to do more checks and be more aware to not get yourself in that mess in the first place.

Skills are another one. Ensure that you never kick up the silt through keeping up standards, correct weighting, etc.

It's nice to dive with others sometimes. It's also great to dive on your own and mooch around at your own pace.


Vive la difference! As some Gallic people say.

Back to TDI and helitrox.

We agree on that.

 

[Tracy]

Well except you're double digit ATAs away from HPNS at normoxic O2 concentrations.

His statement didn't mention depth. It just stated the only reason to avoid it was cost.
There are other reasons.

 

[rjack321]

His statement didn't mention depth. It just stated the only reason to avoid it was cost.
There are other reasons.

20/80 is a thing, although not in recreational scuba. HPNS still not an issue

 

[sea_ledford]

For a 150ft dive 21/79 would have less risk from gas density and no narcosis (depending on if o2 is narcotic) than 21/35 or 21/20 and based on current research the increase in decompression time prescribed by the currently algorithms is likely incorrect.

Unless there has been something that has come out in the last couple years that I missed, I don't think that was the takeaway. Mitchell was pretty specific in saying that the reasons we are doing extra deco with higher FHe may be incorrect, but the amount of deco seems to be correct.

A 150' for 30 min dive with 21/79 gives a run time of 163 minutes
A 150' for 30 min dive with 21/35 gives a run time of 89 minutes
(with GF 40/65)

 

[rjack321]

Unless there has been something that has come out in the last couple years that I missed, I don't think that was the takeaway. Mitchell was pretty specific in saying that the reasons we are doing extra deco with higher FHe may be incorrect, but the amount of deco seems to be correct.

A 150' for 30 min dive with 21/79 gives a run time of 163 minutes
A 150' for 30 min dive with 21/35 gives a run time of 89 minutes
(with GF 40/65)

Just maybeeeee add deco gas here...

 

[flymolo]

If you're used to someone checking you over before jumping in, you'd naturally become less attentive because someone else helps out. OK, you may have a team that "fines" you or mercilessly takes the piss because of some small issue -- that drysuit hose -- but most of the time people will just point it out and even connect it for you. Kind of they give you a fish to eat, not let you fish for it yourself.

It doesn't sound like you're familiar with team checks. When we do checks as a team, everyone suits up on their own, and the team check is a brief sequence that we run through together just prior to splashing. It covers all the bases so nobody jumps in with a disconnected hose, a closed valve, or an unsafe po2. It takes less than a minute to do this and still be methodical. Contrary to what you said, we are attentive because we prefer to not put ourselves or each other at risk by forgetting something important.

 

[lostsheep]

It doesn't sound like you're familiar with team checks. When we do checks as a team, everyone suits up on their own, and the team check is a brief sequence that we run through together just prior to splashing. It covers all the bases so nobody jumps in with a disconnected hose, a closed valve, or an unsafe po2. It takes less than a minute to do this and still be methodical. Contrary to what you said, we are attentive because we prefer to not put ourselves or each other at risk by forgetting something important.

Is it the checklist or the number of divers that adds to safety?

If it’s the team, what is the optimum number of team mates for maximum safety? Is 3 better than 2? 4 better than 3?

 

[flymolo]

Is it the checklist or the number of divers that adds to safety?

If it’s the team, what is the optimum number of team mates for maximum safety? Is 3 better than 2? 4 better than 3?

I'd say it's a combination. Of course I'll still run through checklists diving solo but it helps to have teammate(s) as multiple brains work better than 1.

3 is the max team size. If there are 4 divers it's better to split into 2 teams of 2 to prevent things like diffusion of responsibility or overcrowding in a tight space. A team of 3 is better than a team of 2 because if one diver becomes compromised you have 2 people to support. Or one to support and the third to assist with maintaining situational awareness etc.

 

[sea_ledford]

Just maybeeeee add deco gas here...

That is actually with O2 as deco. Didn't say it was a realistic plan, just pointing out that adding more helium is not an all gain and no pain situation.

 

[lostsheep]

I'd say it's a combination. Of course I'll still run through checklists diving solo but it helps to have teammate(s) as multiple brains work better than 1.

3 is the max team size. If there are 4 divers it's better to split into 2 teams of 2 to prevent things like diffusion of responsibility or overcrowding in a tight space. A team of 3 is better than a team of 2 because if one diver becomes compromised you have 2 people to support. Or one to support and the third to assist with maintaining situational awareness etc.

My question was quasi rhetorical.

If you will occasionally skip the team but you never skip the check, then clearly one is more important than the other.

I think at least one agency insists on the team check to remind themselves of the edge they have