Is Deep Air / Light Deco (bounce?) Discussible on ScubaBoard?

[dumpsterDiver]

The internet seems to promote a race to the bottom of stupidity everywhere else, so why not here?

I really miss GI3 sometimes...

So what happened to him?

 

[eternaljonah]

just to make things clear, am only curious about how it all works, not planning a multitank dive, but if you are doing a multitank dive with say ean25 for bottom gas and ean80 for deco. why not keep the ean80 tank valve closed till you need it. would prevent you breathing it by mistake at the bottom.....

 

[DevonDiver]

IIRC, Thal once described one part of the Scientific Diver cert system as the ability to free ascend from your certified depth; to get a 50 m cert one must free ascend from 50 m, and probably not just once.

I don't really understand what that proves in a scuba context?

NDL bottom-time is so negligible at that depth, as to render the possibility of a safe free-ascent pretty much null-and-void. An incident would have to occur on, or immediately following, the descent. Anything beyond that...and a free ascent from depth would involve blown deco.

Also, I see a big disconnect in terms of performance, when comparing doing such an ascent wearing full scuba gear, compared to an unencumbered free-diver. Of course, if the ascent could be achieved whilst wearing scuba kit (rather than a free dive), then fair enough.

Having said that, I wouldn't be prepared to do a practice free-ascent from 50m for anyone's cert card. I'd tackle the issue the other (more obvious) way.. and ensure I was trained and equipped to deal with problems at that depth - adopting the mindset that the surface wasn't an option and that the dive required a different approach from the recreational diving mentality that sees the surface as an immediate safe-haven.

 

[DevonDiver]

just to make things clear, am only curious about how it all works, not planning a multitank dive, but if you are doing a multitank dive with say ean25 for bottom gas and ean80 for deco. why not keep the ean80 tank valve closed till you need it. would prevent you breathing it by mistake at the bottom.....

You would pressurize and shut-off the tanks. Every agency I know of teaches some form of gas-switch drill, which includes a formalized, pre-set routine for changing gasses/regulators. These drills include the re-pressurization of the tank about to be used.

For instance, the TecRec (PADI) technical course/s teach:

N -- Note your name and the maximum depth on the cylinder labels (if picking up a staged cylinder, you may do this as you retrieve the cylinder).
O – Observe the actual depth and compare it to the maximum depth on the label.
T - Turn open the valve. Check the cylinder pressure.
O - Orient the second stage by pulling it from the retaining bands, and tracing the hose from the first stage to the second so there’s no doubt you have the right one. Unblock the mouthpiece (if using a block), test purge the regulator and then switch to the new gas.
X - Examine your team mates. Follow the hose from their mouthes to the cylinders and check the markings on the cylinders and compare them with the actual depth.

 

[TSandM]

At some point though, I would think that we need to recognize that people who survive deep diving despite their lack of training, knowledge and appropriate gear are probably not the best people to give advice on this topic. Just as I think we would all agree that a diver who survives overhead penetration dives despite their lack of training, knowledge and appropriate gear are not the best people to give advice on cave diving.

Bravo!

just to make things clear, am only curious about how it all works, not planning a multitank dive, but if you are doing a multitank dive with say ean25 for bottom gas and ean80 for deco. why not keep the ean80 tank valve closed till you need it. would prevent you breathing it by mistake at the bottom.....

In fact, that's how it works. If you are diving bottom mix in backgas, and slinging a bottle with deco mix, the deco bottle is turned off until you are ready to use it. This is not only to prevent its inadvertent use at the wrong depth (which is actually prevented by procedure) but also to prevent accidental gas loss during the dive, such that you reach deco depth without any gas on which to deco.

 

[PfcAJ]

Diving air deep is like driving drunk fast. It can be thrilling, but you are more than likely to wind up in trouble. There was a time when there was no option. But now there is - helium.
So why not use it ?

Nickel rocketry and false bravado.

 

[gsk3]

I have free dived to ~102', twice, and I still make 75' without much thought or effort. With EAN25 and using "my" nitrox training (1.6/1.8) my computer shows a max "working" depth of 178', and I think a half breath at 178' is significantly more than a full breath at the surface.

Do you really dive to a ppO2 of 1.8? That alone shows either your training is outdated or you have an extremely high risk-tolerance, or both.

 

[lamont]

Do you really dive to a ppO2 of 1.8? That alone shows either your training is outdated or you have an extremely high risk-tolerance, or both.

I'll be there's someone out there in the world still willing to train halemano to 2.0, so then he could push it even further, and still be able to stand by the fact that he was 'trained' by someone else and so therefore it must be okay...

[ ...and this really points out another problem with deep air -- it tends to be symptomatic of the diver in general believing that they're smarter than everyone else and the rules don't apply to them... ]

 

[String]

Diving air deep is like driving drunk fast. It can be thrilling, but you are more than likely to wind up in trouble. There was a time when there was no option. But now there is - helium.
So why not use it ?

Because in large chunks of the world its not available at all and in other areas it makes the cost of a dive prohibitive.

 

[Potapko]

Diving air deep is like driving drunk fast. It can be thrilling, but you are more than likely to wind up in trouble. There was a time when there was no option. But now there is - helium.
So why not use it ?

From the perspective of the people I dive with that is simple. Price and availability. The majority of which earn 1,ooo-$1500 per month. They have a chance to do a wreck dive to 50 meters for $20 on air or not do the dive because it costs 2 days pay.

So they do the dive on air.

Is that a valid reason? For some of you no, for many of us, yes.