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Inhaled, or exhaled, I've found that with practice it makes little difference to me.
Spare Air: some thoughts
- Thread starter fdog
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My fault, I obviously gave you too much credit.
I cannot comment on what others have stated, but I will try to explain the free ascent target ranges (FATR) of myself and my students. One important aspect to this is it assumes that the Diver has a full-breath of air at the beginning of the free-ascent / CESA.
All of my basic students must attempt a free-ascent (regulator in-mouth and air available) from a depth of 50' to the surface. Advanced students do their CESA from 115' to the safety stop. I would estimate that half the basic students and one in three advanced students are successful in their attempt. The BC is empty and they are negatively buoyant at depth, so they must swim beside the instructor to maintain a maximum ascent rate of 30 fpm. The exercise is undertaken primarily to teach technique and for them to gain appreciation for depth and what it means to them in an emergency.
As a Navy diver, training consisted of doff and don of scuba at 100' and a free ascent from 100' after exhalation. I have often attempted a free-ascent in the range of 170 to 180' (from 200' or so to my decompression stop). On a full breath, I have been mostly successful, but not in all cases. If I didn't have a breath to start, there is no way I would be successful deeper than 100', probably shallower as I don't possess the fitness of my youth.
I think it arrogant to believe that you may not need another breath of air to safely perform a free-ascent from depth. One cannot be assured that you will start the process with a full breath to begin with.
Without another source of air, it is reasonable to assume that a diver will ascend too quickly in an OOA/ 1st stage malfunction situation. At the very least a secondary source of air will allow the Diver to slow his/her ascent and possibly prevent DCS or AGE. A secondary air source, just makes good sense.
It may matter more that a secondary air source exists, rather than the size of this source. The bottom line is that the secondary air source will provide you with enough air to get to the surface safely. Obviously if you are diving with an overhead, such as a cave, wreck or under the ice, a Spare Air is insufficient. If however you dive in open-water, it may provide you with enough air to insure safety. That said, so will a Pony Bottle or other secondary cylinder. You just have to decide what you want to take with you on your next diving vacation.
Reg Braithwaite
Contributor
I cannot comment on what others have stated, but I will try to explain the free ascent target ranges (FATR) of myself and my students. One important aspect to this is it assumes that the Diver has a full-breath of air at the beginning of the free-ascent / CESA.
All of my basic students must attempt a free-ascent (regulator in-mouth and air available) from a depth of 50' to the surface. Advanced students do their CESA from 115' to the safety stop. I would estimate that half the basic students and one in three advanced students are successful in their attempt. The BC is empty and they are negatively buoyant at depth, so they must swim beside the instructor to maintain a maximum ascent rate of 30 fpm. The exercise is undertaken primarily to teach technique and for them to gain appreciation for depth and what it means to them in an emergency.
As a Navy diver, training consisted of doff and don of scuba at 100' and a free ascent from 100' after exhalation. I have often attempted a free-ascent in the range of 170 to 180' (from 200' or so to my decompression stop). On a full breath, I have been mostly successful, but not in all cases. If I didn't have a breath to start, there is no way I would be successful deeper than 100', probably shallower as I don't possess the fitness of my youth.
I think it arrogant to believe that you may not need another breath of air to safely perform a free-ascent from depth. One cannot be assured that you will start the process with a full breath to begin with.
Without another source of air, it is reasonable to assume that a diver will ascend too quickly in an OOA/ 1st stage malfunction situation. At the very least a secondary source of air will allow the Diver to slow his/her ascent and possibly prevent DCS or AGE. A secondary air source, just makes good sense.
It may matter more that a secondary air source exists, rather than the size of this source. The bottom line is that the secondary air source will provide you with enough air to get to the surface safely. Obviously if you are diving with an overhead, such as a cave, wreck or under the ice, a Spare Air is insufficient. If however you dive in open-water, it may provide you with enough air to insure safety. That said, so will a Pony Bottle or other secondary cylinder. You just have to decide what you want to take with you on your next diving vacation.
Great post, I wish I'd read this as part of my OW training. Amongst other things, it would have helped me to understand the 60' limit for OW divers. It appears that you are addressing a CESA as the only alternative to carrying redundant air. This makes a certain amount of sense when discussing FATR, but I wonder if your conclusion is making a few simplifying assumptions that may hold for many but not all divers.
As part of my training after AOW, I was required to practice an out-of-gas swim after exhaling to simulate the worst case OOG. I was required to swim to my instructor (who was swimming away from me slowly), signal OOG, and share air. This simulates an OOG situation where you have a buddy, you have the situational awareness to know where they are, but you are only loosely following them.
Like the FATR, I now have an idea of how far I can swim horizontally to another diver to get air. Am I correct in thinking that if stay well within this range and continue to practice out of air swims that I have a realistic secondary air source?
Of course, I am not suggesting that doing so works for all divers. It appears (from reading this thread) that some divers may not have practiced an out of air swim. Others appear to consider maintaining contact with a buddy to be an onerous burden. I am personally ok with it and typically follow the DM around when on vacation without a buddy.
On my recent trip to Conzumel we did the notorious "Barracuda" reef, a site known for being deep by NDL diving standards and for its current. Separation is a concern. I was happy to stay very close to the DM leading the dive, I viewed the cylinder on his back as my pony bottle. Many others may have preferred the freedom to swim a bit more freely.
Reg, I believe it's save to say that your instruction was more comprehensive than the greatest majority of all divers taking an entry SCUBA Program. I sincerely congratulate your instructor for making the extra effort to expand the scope of his training.
Please do not misinterpret my comments. In any program that I've taught, be it military, commercial, or recreational diving, I will fail a person in open-water if they are beyond touching distance from their buddy unless instructed otherwise (CESA). I'm a strong supporter of the buddy system and team diving in most circumstances. That said, I have failed to do this personally, despite my best efforts to do so. Simply put, people make mistakes and get separated.
Some divers dive in less than ideal visibility. There are times when I've inadvertently lost my buddy to currents or silting. You can't swim to someone if you don't know in which direction to swim...
I consider my closest source of back-up air my own and dive with redundancy. Many years ago however, this was not the case. When I first started diving I used a J-Valve and sometimes a K-Valve (no reserve) without a SPG. When you were out of air, you were out. You looked at your buddy back then in a different light than many divers do today.
What I'm suggesting here is:
1. Always dive with a Buddy;
2. Always stay together;
3. Practice OOA drills as a donor and receiver via octopus and buddy breathing; and
4. If you so choose, carry a secondary air-source whether it be a Spare Air or a Pony Bottle. Understand this is for emergency use only! Practice with it, be comfortable.
5. Dive within your depth envelope and gain experience.
PADIs decision to no longer teach buddy breathing places a higher priority on having a secondary breathing source imo. In any regard, I believe that the selection of diving equipment is a personal one and don't appreciate any disparaging comments made by people on the equipment choices of other divers.
When Larry Williamson of Submersible Systems told me his story, the words "What I wouldn't give for just one more breath of air!" resounded in my mind. I have been in this situation underwater on more than one occasion and have felt as he did. For someone to argue that an additional breath is insufficient, tells me that that person hasn't been in this situation. They have no credibility in my view.
Spare Air like most pieces of diving equipment I've used, has a limited operational envelope. For the sake of repeating myself, "You use the right tool for the job." If I'm flying away on vacation to do some recreational diving, I take a Spare Air with me. It will give me enough air to get to the surface within the diving envelope I'm diving. A couple of extra breaths is a luxury in an emergency and it's all I'll need in most situations.
Not saying SpareAir doesn't serve a purpose in some "limited operational envelope" as mentioned above, nor that you don't need to stay near your buddy, but I think if most people spent as much time and effort focused on thinking/planning/gearing/practicing how to AVOID the problem in the first place as they do focusing on what to do after it's too late...they'd be far better off.
:shocked2:
See ya round; gotta go buy a padded suit and practice jumping out of a moving car so I'll be prepared when my brakes fail.
Of course there's the less pretentious philosphical version:
"You can't fix stupid."
Reg Braithwaite
Contributor
Well, the out-of-air swim was not part of OW or AOW, it was part of a course dealing with certain aspects of deep NDL diving offered by IANTD. IIRC, you have to demonstrate that you can swim underwater a certain distance to pass PADI OW, but I do not recall practicing swimming in full gear on empty lungs for my PADI OW or the deep dive in my PADI AOW. or even my PADI Rescue Diver.
I'm sure that's true, but I still worry about mechanical failures, especially when my regs are screwed into a resort's valve and tank or when I take my own gear into cold water where free flows are an ever-present worry. So I may not need to practice leaping from a moving car, but I do need to know how to thumb a ride if the engine quits
"I'll never be in any diving situation that's beyond my control!!!"
Cocky or just inexperienced?
Re-read what I wrote.
I did not say "I'll never get into such a situation" but rather I said exactly the opposite: "spend as much time and effort" avoiding such situations as you do preparing for what to do if they occur.
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