Deep Air Dives In Tech Classes

[tomfcrist]

I didn’t say that. And the bulk of my training is with iantd.

If you think you have to take people that deep in air you are mistaken. You don’t.

I don’t assume you have to take anyone that deep on air. I also don’t assume people who choose to go that deep on air are “stupid”.

 

[LiteHedded]

I don’t assume you have to take anyone that deep on air. I also don’t assume people who choose to go that deep on air are “stupid”.

I don’t either. I think they’re making the dive more dangerous than it needs to be because they’re nickel rockets or thrill seekers.

The dives are stupid. There are people who are smart and should know better doing the dives. What’s worse, the ones who promote that type of diving to people who don’t know any better

 

[tomfcrist]

There you go again, dives to 50m on air are stupid? No dude, they aren’t. Let’s not pretend that some mysterious narcosis monster inebriates you at 101’ and you are automatically incapable of critical thought.

Like I alluded to before, there’s a difference between 160 on air in cold/darkwater and 80degree 100ft vis. Example 1 is sketchy, example 2 is done all the time...and frankly isn’t that big a deal. Would helium be advantageous in both examples? Of course. Is it inherently stupid to dive those dives without helium? Come on dude, get a grip.

 

[leadduck]

Couple of thoughts:

1) AFAIK you don't have to go to 50m on air with PADI Tec50. On the last dive of the 12 dives of the Tec40-45-50 course you may go to 50m on air, but you don't have to and 40m max.depth is sufficient for all dives. Tec50 is about handling deco with two stages before going into Trimix below 40m. Tec50 is not to promote deep air. (PADI Tec instructors please correct me if wrong ...)

2) If you feel narcosis during an easy open water reef dive, you can go shallower immediately, problem solved. No such solution in a cave or wreck penetration, hence no surprise that cave diving training orgs such as GUE are very conservative in that regard and recommend helium starting at 30m.

 

[LiteHedded]

There you go again, dives to 50m on air are stupid? No dude, they aren’t. Let’s not pretend that some mysterious narcosis monster inebriates you at 101’ and you are automatically incapable of critical thought.

Like I alluded to before, there’s a difference between 160 on air in cold/darkwater and 80degree 100ft vis. Example 1 is sketchy, example 2 is done all the time...and frankly isn’t that big a deal. Would helium be advantageous in both examples? Of course. Is it inherently stupid to dive those dives without helium? Come on dude, get a grip.

Agree to disagree. Yea I think it’s completely stupid to dive impaired when you might be called upon to solve complex problems. Maybe you’re not stupid (congrats if not!). Those dives are

 

[Kevrumbo]

Couple of thoughts:

1) AFAIK you don't have to go to 50m on air with PADI Tec50. On the last dive of the 12 dives of the Tec40-45-50 course you may go to 50m on air, but you don't have to and 40m max.depth is sufficient for all dives. Tec50 is about handling deco with two stages before going into Trimix below 40m. Tec50 is not to promote deep air. (PADI Tec instructors please correct me if wrong ...)

2) If you feel narcosis during an easy open water reef dive, you can go shallower immediately, problem solved. No such solution in a cave or wreck penetration, hence no surprise that cave diving training orgs such as GUE are very conservative in that regard and recommend helium starting at 30m.

Recap:

Note that the depth/pressure of 40meters/5 ATA happens to be the long established recreational depth limit. With regard to CO2 retention, there finally appears to be scientific validation for this: The Gas Density of Air at the surface is approx 1.2 to 1.3 grams/liter; but at 5 ATA this value is five times as much or 6.0 g/L. A gas density over 6 g/L has been found to increase susceptibility to CO2 retention/acute Hypercapnia along with potential increased risk of Oxygen Toxicity, especially during instances of high intensity physical exertion and increased work-of-breathing (WOB).

Finally, there is a fundamental and dangerous flaw not taken into account in the whole PADI Tec 40/45/50 course progression & certification to begin with: The Density of Bottom Gas Nitrox 24% to 21% for a max working ppO2 of 1.2 bar is 6 g/L and higher, with Tec 50 and an elective choice of Air at a whopping 7.2 g/L. (Refer again to article: Advanced Knowledge Series: The Gas Density Conundrum | Dive Magazine )

The point is again: There's no safety margin left at all for the hazards of CO2 retention and narcosis problems that arise with unforeseen heavy physical activity and increased WOB at these certification depths of 40/45/50 meters on primarily non-Helium, high gas density Oxygen-Nitrogen Blends (essentially Extended Range Deep Air). And to recover at depth from CO2 retention, you need plenty of bottom gas and some minutes time to relax & regain a normal non-exertion respiratory rate -if possible- before safely aborting the dive and nominally ascending to any required deco stops.

 

[leadduck]

And to recover at depth from CO2 retention, you need plenty of bottom gas and some minutes time to relax & regain a normal non-exertion respiratory rate -if possible- before safely aborting the dive and nominally ascending to any required deco stops.

From understanding that mechanism it seems to me that recovering at depth (say 50m) from CO2 retention with deep air won't work and you better ascend immediately. Quite similar to narcosis in that regard, isn't it?

 

[MaxBottomtime]

Recovery from CO2 retention does take awhile but can be achieved on the bottom or during the ascent. CO2 narcosis comes on very quickly but can be handled with two or three slow deep breaths.

 

[Kevrumbo]

From understanding that mechanism it seems to me that recovering at depth (say 50m) from CO2 retention with deep air won't work and you better ascend immediately. Quite similar to narcosis in that regard, isn't it?

Recovery from CO2 retention does take awhile but can be achieved on the bottom or during the ascent. CO2 narcosis comes on very quickly but can be handled with two or three slow deep breaths.

Notwithstanding a Rebreather Scrubber malfunction and immediate Open Circuit bailout -you have to cease and desist the physical exertion that's causing the spiraling hyperpnea into CO2 retention. The concomitant CO2 narcosis ("dark narc") is synergistic and/or additive to the already N2 narcosis, and further debilitating to your cognitive senses & situational awareness.

Tactically if possible IMO/IME, I would try to get my breathing rate and homeostatic respiratory metabolism back to nominal -having enough gas and time- before ascending to any required deco stops and the surface. . .