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Scuba air Vs normal air?

DylansFinest

Member
May 8, 2017
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21
Curacao
Lately I have been freediving a lot. I quickly learned that you can ascend pretty fast as long as you can equalize properly. with scuba diving this isn't the case. My question is : Why aren't there as much medical risks in ascending rapidly with freediving but with scuba diving there is/What are the effects of scuba air compared to normal air?
 

cdavis

Well-Known Member
Jan 21, 2003
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Its not the air, its the time down. Scubies accumulate much more N2 than freedivers. Slow ascents reduce bubble formation. Freedivers can get in trouble with DCS too, but it takes a very good freediver, diving deep and/or multiple,very long dives.

Welcome to DB.
 

Bill McIntyre

San Clemente, CA
Staff member
Forum Mentor
Jan 27, 2005
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If you've had scuba training, you should already know this, but it wasn't clear to me from your question so I'll say it.

If you breath from scuba, you breath air at ambient water pressure. For instance at 33 feet, you are at two atmospheres of total pressure. If you held your breath and swam to the surface the air in your lungs would double in volume, rupture the lung tissue, and kill you. Even without holding your breath, it might be possible to ascend faster than you were blowing off expanding air and cause the embolism.

If you already knew that, forgive me for stating the obvious.

Edit- I juist read your introduction- you do know that.
 
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DylansFinest

DylansFinest

Member
May 8, 2017
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Curacao
If you've had scuba training, you should already know this, but it wasn't clear to me from your question so I'll say it.

If you breath from scuba, you breath air at ambient water pressure. For instance at 33 feet, you are at two atmospheres of total pressure. If you held your breath and swam to the surface the air in your lungs would double in volume, rupture the lung tissue, and kill you. Even without holding your breath, it might be possible to ascend faster than you were blowing off expanding air and cause the embolism.

If you already knew that, forgive me for stating the obvious.

Edit- I juist read your introduction- you do know that.
Hahaha Thanks anyway!
 
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DylansFinest

DylansFinest

Member
May 8, 2017
7
1
13
21
Curacao
Its not the air, its the time down. Scubies accumulate much more N2 than freedivers. Slow ascents reduce bubble formation. Freedivers can get in trouble with DCS too, but it takes a very good freediver, diving deep and/or multiple,very long dives.

Welcome to DB.
Ohhhh that makes sense. Okay I got it now thanks!
 

Bill McIntyre

San Clemente, CA
Staff member
Forum Mentor
Jan 27, 2005
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San Clemente, CA
OK, now that I'm in my place, I'll bore you with some trivia that cdavis didn't mention.

I got my first scuba tank in 1954, and while DCS was well understood in scuba diving, it was thought to be impossible for a freediver to suffer from it. As far as anyone knew, you had to breath compressed air. A retired Navy Master Diver named E.R. Cross used to write a diving tech column in Skin Diver Magazine, and in 1962 he described a problem encountered by pearl divers in Tuamotu and other South Pacific islands. It was called Travana, and the symptoms were what we now recognize as DCS, including crippling in some cases. It looked like the bends, but it couldn't be since they were not breathing compressed air. But Cross had one of what I think was the earliest dive computers made by Scubapro, and he decided to do some simple tests. He just lowered the thing over the side on a string to duplicate the dive depths, times, and surface intervals that he had observed in the pearl divers, and sure enough the computer got bent. Or to be more precise, it said it needed decompression stops. So as I recall (and my memory is not razor sharp after all these years) this was the first time that it was known that freedivers could actually get DCS.

I'm a bit out of my league here but I don't think its a problem for pure competitive freedivers since they are not doing repetitive dives. Please correct me if I'm wrong cdavis or anyone else who knows better. But highly competitive champion spearfishermen have indeed suffered DCS in competitions.

There are a lot of things I worry about while spearfishing, including the fact that a woman got her hamstring removed by a great white shark last week near one of my favorite kelp beds, but I'm afraid that DCS is not one of them.

Edit- after mentioning it, it occurred to me that someone might like to hear about the shark.
https://forums.deeperblue.com/threads/southern-california-shark-attack.108799/
 
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DylansFinest

DylansFinest

Member
May 8, 2017
7
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21
Curacao
OK, now that I'm in my place, I'll bore you with some trivia that cdavis didn't mention.

I got my first scuba tank in 1954, and while DCS was well understood in scuba diving, it was thought to be impossible for a freediver to suffer from it. As far as anyone knew, you had to breath compressed air. A retired Navy Master Diver named E.R. Cross used to write a diving tech column in Skin Diver Magazine, and in 1962 he described a problem encountered by pearl divers in Tuamotu and other South Pacific islands. It was called Travana, and the symptoms were what we now recognize as DCS, including crippling in some cases. It looked like the bends, but it couldn't be since they were not breathing compressed air. But Cross had one of what I think was the earliest dive computers made by Scubapro, and he decided to do some simple tests. He just lowered the thing over the side on a string to duplicate the dive depths, times, and surface intervals that he had observed in the pearl divers, and sure enough the computer got bent. Or to be more precise, it said it needed decompression stops. So as I recall (and my memory is not razor sharp after all these years) this was the first time that it was known that freedivers could actually get DCS.

I'm a bit out of my league here but I don't think its a problem for pure competitive freedivers since they are not doing repetitive dives. Please correct me if I'm wrong cdavis or anyone else who knows better. But highly competitive champion spearfishermen have indeed suffered DCS in competitions.

There are a lot of things I worry about while spearfishing, including the fact that a woman got her hamstring removed by a great white shark last week near one of my favorite kelp beds, but I'm afraid that DCS is not one of them.

Edit- after mentioning it, it occurred to me that someone might like to hear about the shark.
https://forums.deeperblue.com/threads/southern-california-shark-attack.108799/
Very interesting. good to know.
 

cdavis

Well-Known Member
Jan 21, 2003
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Sarasota, Fla
Ahh, the ScubaPro dive computer. I had one, useful gadget, but we began calling it the "bends-o-matic." The thing was very good for a single dive, but for repetitive dives, it greatly underestimated the N2 load. For something like testing freediving, I'm pretty sure it would way underestimate the danger.
 

cdavis

Well-Known Member
Jan 21, 2003
3,961
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Sarasota, Fla
I'd be curious how a modern computer, more accurate on repeat dives, would react to what Cross did. For sure it would have showed an even worse (more bent) result. Given how common and severe Travana can be, it probably would show need for a whole bunch of deco. Just how bad could it really be?

I suspect that getting bent freediving is not as uncommon as believed. A friend of my got hit with a mild case from repetitive long dives in 60 ft or so combined with an airplane ride. How many others?
 

Deano 647

Member
Jul 29, 2019
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Melbourne
SNIP in 1962 he described a problem encountered by pearl divers in Tuamotu and other South Pacific islands. It was called Travana, and the symptoms were what we now recognize as DCS
SNIP
Indeed Bill The name 'taravana' came from the Polynesian expression to 'fall down crazy' quiet descriptive ! ;-) There has been quite some research done on the Ama divers in Japan and it is well documented that pearl divers in Broome who were breath hold diving in the late 1800s, pre Standard Dress surface supply, got horribly bent, with many fatalities and permanent crippling.
 
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