What is the fundamental reason that prevents scuba diving from becoming popular?

[Celt]

Yep it beats drowning, but it's a long way up and you have to go fast to make it. The expansion of gas is something else even when fully exhaling. And we used the air in the crack bottles to breathe from the BC. I can still taste the bladder disinfectant. I think it was a solution of Detol or Milton. But I'm not going to cleanup my old Nemrod or Fenzy BC or throw away my redundancy any day soon. When I head off solo later today I'll side mount 2 lovely 7ltrs and be happy as Larry.

 

[El Diablo]

Made a CESA from 40m about 30 years ago and it's not nice and can go very wrong. So definitely don't bother with it if possible. The idea of breathing from the BCD I think came from the use of crack bottles on the early BC,s but people got sick from bacteria in the bladders so that's a bad idea too. My old Nemrod

Hi Mac, initially the breathing techniques were ditched because of the CO2 cartridges on the early shoe horse style BCDs like the one you are displaying. Bacteria buildup and infection actually are not so prevalent.

Hypoxia and Hypercapnia from rebreathing the same air at depth render this technique extremely dangerous. As Boulderjohn mentioned, slowly exhaling air during ascent will reduce the buildup in our receptors instead of increasing the urge to breathe and create convulsions by holding it or rebreathing the same air.

Please don't get me wrong, I am not trying to 'school' you, I am adding this information for the 2 other "experts" that don't understand basic physiology.

 

[El Diablo]

Just as a final point, I believe that almost all agencies do a very poor job teaching emergency ascents. During my 17 years as professional, I have twice had extensive discussions with PADI about this. I did not convince them either time, and they did not convince me. The main benefit to those discussions is that I really know well what their beliefs are.

One problem I have is that they do not include the information I posted above about the regulator being able to deliver air during the ascent. Their explanation for that is that while it may be true in a normal OOA ascent, it is possible that there was some sort of regulator failure that would make it inoperable at any depth. (That is what they are really training you for--a truly rare regulator failure, not going OOA.)

A second problem is the exercise they do in the pool sessions called the air depletion exercise. In that exercise, the instructor is supposed to shut off the student's air, and the student is supposed to signal OOA upon realizing they have no air. I imagine that for the last couple decades, people have wondered what the point of that might be. Well, if you go back and read the literature when the idea was first hatched, you see the point of it. Regulators were not as good then, and it would feel harder to breathe as you got close to zero. The point was to get you to recognize that you were about to run out of air so you could prepare for it. With modern regulators, you will not experience that with your air shut off in the bottom of a swimming pool. It will, however, happen at depth with a tank that is low on air. You should have a warning of a couple breaths before you are OOA. The air depletion exercise teaches students the opposite of its original intent. (In this exercise, you can mimic a true OOA experience by almost, but not quite, shutting off the student's air. In that case, they will feel it getting harder to breathe.)

The main problem is the horizontal CESA in the pool. Students have to swim relatively slowly for 30 feet while exhaling the whole way. Most students find that difficult, and instructors resort to a host of tricks to get them to make it the whole way. Many have to try it more than once to make it. It is difficult because even if they ascend on a diagonal from the deep end of the pool, they are not getting the true expanding air experience. This teaches them the exact wrong thing--in a real emergency from any deeper than that, I won't make it!

A joint PADI/DAN study about a decade ago found that the most common cause of death in a scuba accident (not talking about things like heart attacks) is an air embolism following a panicked ascent to the surface, usually following an OOA incident. In other words, the divers likely died because they held their breath doing an emergency ascent after going OOA. I fully believe that many of those deaths were caused by the "I'm never going to make it!" belief instilled in students during their initial training.

I would like to add that many non-balanced regulators like the Scubapro MK2 still get 'harder' when the pressure drops close to zero.

I also wrote previously that removing the regulator to switch to the BCD hose is a bad idea because
A) its flooded and needs clearing and B) the second stage will still deliver air during ascent as ambient pressure drops. Can you please clarify if this is not teached anymore during OWD?

 

[Celt]

Hi Mac, initially the breathing techniques were ditched because of the CO2 cartridges on the early shoe horse style BCDs like the one you are displaying. Bacteria buildup and infection actually are not so prevalent.

Hypoxia and Hypercapnia from rebreathing the same air at depth render this technique extremely dangerous. As Wibble mentioned, slowly exhaling air during ascent will reduce the buildup in our receptors instead of increasing the urge to breathe and create convulsions by holding it or rebreathing the same air.

Please don't get me wrong, I am not trying to 'school' you, I am adding this information for the 2 other "experts" that don't understand basic physiology.

Yeah I had an old CO2 horse shoe. The one in the photo like the Fenzy used a compressed air crack bottle that can be filled from your main tank. It was reusable and was tested.

 

[El Diablo]

Yeah I had an old CO2 horse shoe. The one in the photo like the Fenzy used a compressed air crack bottle that can be filled from your main tank. It was reusable and was tested.

AP used to make (maybe they still do) the Buddy Commando that had a separate pony for that...

 

[Celt]

AP used to make (maybe they still do) the Buddy Commando that had a separate pony for that...

When I look at some of the gear I used and think about some of the things I did and admittedly still do, I ask myself would I like to see my son doing them and the answer is NO NO NO

 

[El Diablo]

When I look at some of the gear I used and think about some of the things I did and admittedly still do, I ask myself would I like to see my son doing them and the answer is NO NO NO

I'll introduce my son to diving next year hopefully... having the same thoughts already as I am slowly putting his kit together as we speak

 

[Alaskan Scuba Dude]

he main problem is the horizontal CESA in the pool. Students have to swim relatively slowly for 30 feet while exhaling the whole way. Most students find that difficult, and instructors resort to a host of tricks to get them to make it the whole way. Many have to try it more than once to make it. It is difficult because even if they ascend on a diagonal from the deep end of the pool, they are not getting the true expanding air experience. This teaches them the exact wrong thing--in a real emergency from any deeper than that, I won't make it!

When they feel they won't make it, it's time to ditch the weights.

 

[Alaskan Scuba Dude]

OK so you advise don't do a CESA from 40m when OOA. What other course of action apart from drowning do you recommend.

Sling an AL40 for deeper dives. Common sense prevails.

 

[Blackcrusader]

Sling an AL40 for deeper dives. Common sense prevails.