Dangerous gear?

[John C. Ratliff]

Well, the thread did start to stray a bit and wander some.
My question was only why the Navy taught to deploy the CO2 at depth while the civilian side taught that deploying at depth can lead to an uncontrolled ascent (which is true). Either would be a 'buoyant ascent'. I was wondering how the Navy controlled the ascent with larger and often more numerous cartridges while the civilian diver usually only has a single, small cartridge that he is told not to deploy at depth. What I think I got from this is that apparently the Navy just expected to deal with the aftermath of an uncontrolled buoyant emergency ascent that a civilian would normally avoid.
Anyhow, I think I'll clear out to let the op topic continue.

Duckbill, the answer lies with the "r" phrase in Dr. Stanley Miles' accident equation. The U.S. Navy is willing to assume the risk of a buoyant ascent, whereas USA diving agencies are not. It is as simple as that. I'll tell you though, if I come across an unconscious diver at depth, there will be weights dropped (if I can figure out how to do so on the current BCs) and a buoyant ascent initiated. You cannot do much for an unconscious diver at depth. One other thought is that the new steel tanks, which are ten pounds negatively buoyant, cannot be easily ditched in an emergency. Has anyone else thought of that?

Speaking of tanks, in this thread someone mentioned using an AL 80 tank as a stage decompression bottle. Some people use pure oxygen in their stage tank. I want everyone here to be aware of a hazard involving use of pure oxygen in an AL tank by reading this thread in the Accident Forum on an Oxygen Tank Explosion (click this link). We need to be aware of "traps" whereby a diver thinks he or she is doing something correctly, but is putting themselves in danger through an unknown hazard.

SeaRat

 

[captain]

I don't know if aluminum is the main issue. Most all 100% medical oxygen tanks today are aluminum. There is more to the story than just aluminum.

 

[John C. Ratliff]

I don't know if aluminum is the main issue. Most all 100% medical oxygen tanks today are aluminum. There is more to the story than just aluminum.

Captain, please read the entire thread, especially my post on page 16, #155.

SeaRat

 

[John C. Ratliff]

The Farallon mask (I think it was called the Panoramic) would not seal on my face until I placed a couple of rubber bits between the skirt and frame on the inside. The rubber bits served as spacers that made the skirt deeper. Once I discovered that, the mask fit very well. However, it was probably about the ugliest mask I've ever seen-the frame was safety orange and black.

Couv,

The Farallon mask you talk about was my favorite mask in the 1980s. I don't care much how it looks, but liked it a lot, and it fit my face well. However, I experienced the same problem you describe with it on one I recently bought off E-Bay. I put surgical tubing in that space you describe, and it fit much better. Recently I bought this exact mask, but under the White Stage brand, off E-Bay too. The difference is that the White Stage mask was made of transparent silicone instead of neoprene rubber. It fit me well without the inserts, just like the new one in the 1980s did. Neoprene rubber tends to distort over time. I know this because we fit-tested a worker recently with a large Scott full-face respirator, and he failed even though this was the mask he was fit-tested on the year before. We then compared his mask with a brand new one, and noted a distortion in the rubber seals. So over time the Farallon mask would distort, loose its resilience, and not fit. The White Stage, being made of silicone material, did not distort and still fits. My original mask was destroyed when the LDS installed a purge valve in the skirt rather than the noes pocket, so I've been looking for one and found these two.

SeaRat

 

[Thalassamania]

My memory is that mask (I use a Tekna mask, then Ralph's next one to come out, two pane) came with two black pieces of tubing.

 

[captain]

Captain, please read the entire thread, especially my post on page 16, #155.

SeaRat

John I am well aware of the conditions that can occur with pure oxygen, I worked in the commercial gas industry for Praxair operating a an air seperation unit and 100% oxygen compressors.. Anything will burn in the presents of pure oxygen. Aluminum just burns at a lower temperature than steel. As opposed to scuba equipment oxygen specific valves and regulators are designed to minimize the chance of frictional heating, adiabatic compression and particle impact.
aAuminum contributed to the severity of the incident but was not necessarily a causation.

 

[Kimsey0]

The Russian rebreathers (IDA, etc) *when using* KO2/potassium superoxide (per the original design, on some of them, not all)

 

[Keithth]

You must be conscious about it and must take the serious steps to tackle this problem. In other case the results can be harmful in the future.

 

[Aussiemike]

Hi, I'm new to the Board but not new to diving and I find the comments about free ascents interesting. I taught myself to dive after going snorkelling with a guy who had dive gear. I would dive down to, say, 30 feet, buddy breathe with him for five minutes while going deeper (up to 60 feet) and then free ascend to the surface. If you are doing this under calm, controlled conditions it becomes obvious that you have to breathe out continuously as you can feel the pressure in your chest, throat etc.

You can mimic this sensation by taking an absolutely, totally full breathe while lying on the floor face down and then getting a friend to gently and slowly, while holding onto something fixed, sit on your back. You will find you can't avoid breathing out.

 

[ThomasScherrer]

>You will find you can't avoid breathing out.

that may be true for the experiment you mention.
BUT when scuba diving ALOT more pressure from inside the loungs can block the exhale function,
that is why it is so important to exhale BEFORE the pressure gets too high, when you accent.
this is also why lung over expansion is a known illness most likely to cause death.
breating compressed air under water and swimming up as fast as you normally do when snorkeling is a VERY bad ide !!
also another thing is air bubbles in your blood, they expand too.
it is NOT a problem when the last air you got was from the surface, then you do not make bubbles in blood
and you can not over expand lungs, but offcourse you get a bit limited underwater time.
my best advise is to keep snorking, snorkling,
and keep scuba, scuba, do not mix them, specially at depths you mention.