PfcAJ
Contributor
Thats my understanding, as well, James.
Emergency bailout strategies for recreational diving
- Thread starter DaleC
- Start date
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Great post Dale. There are lots of viable formulas but taking the time to evaluate them and select one is the most important part.
Another part of my dive plan is the time/distance to a treatment chamber. Anybody can take a hit for reasons that science (as opposed to hindsight speculation) cannot currently predict. Most often several failures compound when things go seriously wrong. It is always in the back of my mind that when everything turns south the choice might be drown or get bent.
I figure the odds are pretty-much 100% of drowning after 3-5 minutes with nothing to breath. There is a way better chance I wont get bent at all, and even a higher probability of walking away from the chamber, if I make it to a source to breath. Backup air sources are good and, when done well, will reduce the probability that I will have to make that unpleasant choice but not to zero. The issue is when they all fail I wont have much time to debate the options.
I plan to continue practicing free ascents as long as I can still dive. I would consider having to make one a personal failure, but one I can live with.
I would dearly love to dive the Doria again, for fun this time. But I wont without a chamber onboard and people I trust to run it. Each person has to choose their own formula for that depth/time/distance-to-treatment relationship, but the important part is selecting one as part of your dive plan.
Another part of my dive plan involves basic seamanship. What can I do to help save the vessel if she decides to take up my sport? Secondarily, what happens when our efforts fail or she joins me while Im on the bottom? The only book I recall that addresses these issues in any detail is Gary Gentiles Advanced Wreck Diving Guide. Does everybody remember where they told you the EPIRB was after two great dives and lunch?
Another part of my dive plan is the time/distance to a treatment chamber. Anybody can take a hit for reasons that science (as opposed to hindsight speculation) cannot currently predict. Most often several failures compound when things go seriously wrong. It is always in the back of my mind that when everything turns south the choice might be drown or get bent.
I figure the odds are pretty-much 100% of drowning after 3-5 minutes with nothing to breath. There is a way better chance I wont get bent at all, and even a higher probability of walking away from the chamber, if I make it to a source to breath. Backup air sources are good and, when done well, will reduce the probability that I will have to make that unpleasant choice but not to zero. The issue is when they all fail I wont have much time to debate the options.
I plan to continue practicing free ascents as long as I can still dive. I would consider having to make one a personal failure, but one I can live with.
I would dearly love to dive the Doria again, for fun this time. But I wont without a chamber onboard and people I trust to run it. Each person has to choose their own formula for that depth/time/distance-to-treatment relationship, but the important part is selecting one as part of your dive plan.
Another part of my dive plan involves basic seamanship. What can I do to help save the vessel if she decides to take up my sport? Secondarily, what happens when our efforts fail or she joins me while Im on the bottom? The only book I recall that addresses these issues in any detail is Gary Gentiles Advanced Wreck Diving Guide. Does everybody remember where they told you the EPIRB was after two great dives and lunch?
R
redacted
Guest
I too was initially confused but decided it really means what I would call pressure gradient. That is 0 to 1 (atm), 1 to 2, 2 to 3, etc. So, if you limit depth to less than 60 ft (less than 3 atm) and ascend directly to the surface you are not exceeding the 2 pressure gradient limit (unless you are at altitude).
waterpirate
Contributor
Dale,
I think that a lot of divers that moved on from lemming diving aproached their dives as techreational early on before getting tech training. I know I did. Part of the light bulb moment is realising that redundant gas is really essential beyond your safe and reasonable cesa depth. That thought also goes to your original mention of pg groups. Realising that although the book says your good and padded, further study of the models makes you realise that you should avoid that exercise at all costs. "The birth of a thinking diver" is what we call it when it happens to the recreational guys who go on our 100fsw saturday warm ups for sundays tech dives.
Eric
I have not heard a report from anyone taking an intro to tech from any agency, I would be curious if bailout strategy and pg groups are covered as part of the wake up and smell the neoprene program?
I think that a lot of divers that moved on from lemming diving aproached their dives as techreational early on before getting tech training. I know I did. Part of the light bulb moment is realising that redundant gas is really essential beyond your safe and reasonable cesa depth. That thought also goes to your original mention of pg groups. Realising that although the book says your good and padded, further study of the models makes you realise that you should avoid that exercise at all costs. "The birth of a thinking diver" is what we call it when it happens to the recreational guys who go on our 100fsw saturday warm ups for sundays tech dives.
Eric
I have not heard a report from anyone taking an intro to tech from any agency, I would be curious if bailout strategy and pg groups are covered as part of the wake up and smell the neoprene program?
OP
DaleC
Contributor
Just to clarify, awap you are right. I was using the term pressure groups when I should have said atmospheres. In the text I was reading it was refered to that way but I realize it is a confusing term as the tables mention PG's differently (I will not correct the error in the OP as it will make latter comments confusing).
I have read Haldane's work regarding compartment loading and 2:1 ascent ratios which were later corrected by the inclusion of deep stops but there was also a discussion regarding the direct crossing of atmospheres (<2). It was a different way of looking at ascent profiles from a historical text. Either way, my conclusion takes the theory and translates it into a workable, practical strategy (for me) to be used recreationally. That's all I'm describing. Perhaps some others translate the theory a different way and would like to share their practical interpretation?
Akimbo, your points about chambers are interesting as I remember my "slap the head" moment of understanding the context that USN tables were used. Most of those dives had a chamber on station and there was an acceptable risk of DCS symptoms developing - they expected it. This slight risk did not bother the USN that much because they could be easily resolved via the chamber. I had to rethink my pushing of the tables because, of course, I rarely take a chamber with me on solo dives. In fact my risk of DCS symptoms needs to be 0 so I actually dive quite conservatively as a result and also refer to the DCIEM tables for a sober second opinion. The history of their development is quite interesting as they involved the largest actual dive data base and kept rolling back the limits till the presence of DCS symptoms was nil. As a result they are quite conservative (especially repetitively) compared to USN tables.
I have read Haldane's work regarding compartment loading and 2:1 ascent ratios which were later corrected by the inclusion of deep stops but there was also a discussion regarding the direct crossing of atmospheres (<2). It was a different way of looking at ascent profiles from a historical text. Either way, my conclusion takes the theory and translates it into a workable, practical strategy (for me) to be used recreationally. That's all I'm describing. Perhaps some others translate the theory a different way and would like to share their practical interpretation?
Akimbo, your points about chambers are interesting as I remember my "slap the head" moment of understanding the context that USN tables were used. Most of those dives had a chamber on station and there was an acceptable risk of DCS symptoms developing - they expected it. This slight risk did not bother the USN that much because they could be easily resolved via the chamber. I had to rethink my pushing of the tables because, of course, I rarely take a chamber with me on solo dives. In fact my risk of DCS symptoms needs to be 0 so I actually dive quite conservatively as a result and also refer to the DCIEM tables for a sober second opinion. The history of their development is quite interesting as they involved the largest actual dive data base and kept rolling back the limits till the presence of DCS symptoms was nil. As a result they are quite conservative (especially repetitively) compared to USN tables.
Thanks, DaleC, for initiating this discussion. I began "de-teching" to recreational dive almost exclusively a couple of years ago. Like you, I have been re-thinking my approach to diving, including my "programmed" responses to emergency situations learned from my tech diving training and experiences. I agree with you: Not all of the tech solutions/protocols seem appropriate for rec divers.
Safe Diving,
Ronald
AfterDark
Contributor
Nice post Dale. Youve put a lot of thought into it. Ive done one for real CESA from 70 after less than 5 minutes at depth with no stop; no air, blow and go; with no ill effects, might have pissed myself. When I dive solo I use IDs, Ive never had a failure of my equipment a lesson learned from the 70CESA, borrowed reg failed closed, noticed it right after I exhaled, wasnt much time for planning looked around for my "buddy" nobody so I left. I should mention that my buddy the owner of the reg was nowhere to be found for 45 minutes after I surfaced. He had a nice dive, the SI wasn't so good.
Anyway IDs for solo, and deep with the plan being that if one setup fails the dive is over and my ascent will be determined by the situation, the amount of gas I have, bottom time and if Im boat or shore diving. That could be anything from a non-stop ascent at a quick but safe rate to a leisurely swim up a sloping bottom taking more time than I need even taking a few pics as I swim around at 15 for a few minutes before heading back to shore. I can CESA from 40 easily; deeper than that its IDs solo or not.
Anyway IDs for solo, and deep with the plan being that if one setup fails the dive is over and my ascent will be determined by the situation, the amount of gas I have, bottom time and if Im boat or shore diving. That could be anything from a non-stop ascent at a quick but safe rate to a leisurely swim up a sloping bottom taking more time than I need even taking a few pics as I swim around at 15 for a few minutes before heading back to shore. I can CESA from 40 easily; deeper than that its IDs solo or not.
Getting to the core question in the OP: Dale, to me, "Bailout" implies a catastrophic loss of gas supply.
So, if I'm alone, this becomes a series of decision trees, not a single pre-programed response.
Do I have an available gas supply?
Yes =>Use it
No =>1 to 2 minute CESA
Amount of gas is 1/2 of Rock Bottom?
Yes =>Execute Min Deco ascent
No =>Use gas available to shape ascent as exponential curve
For example, I'm at 90', and my inflator explodes and I start losing gas. In the time it takes to figure out what's going on and disconnect my BC inflator, I drain my aluminum 80 to 300 psi. Woof!
<CESA? NO>
<Gas 1/2 0f Rock Bottom? NO>
<Begin ascent>
<Ascend to 1/2 max depth, expending 1/2 of remaining gas (or 30 fpm whichever is faster)>
<Ascend to 1/4 of max depth, expend half of remaining gas>
<expend remaining gas on slow ascent over remaining depth>
It's not for everyone - this is a process that relies on an intrinsic understanding of curve shaping and Rock Bottom, most typically found in divers that are "those people" - but, it's what I would do if I suddenly found myself inexplicably alone with a gas emergency.
All the best, James
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