Disturbing experience at dive shop
- Thread starter wedivebc
- Start date
Please register or login
Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.
Benefits of registering include
- Ability to post and comment on topics and discussions.
- A Free photo gallery to share your dive photos with the world.
- You can make this box go away
OP
immersion pulmonary edema and it was thought to be quite rare but it seems to come up every now and then.
Immersion Pulmonary Edema | The Heart & Diving - DAN Health & Diving
Aside from the fact that I'm in the caribbean doing some silly stuff myself this week, my only contribution to this thread is that I'd probably have another intermediate "normoxic" range bailout bottle in the mix on a 425 footer myself. But my risk tolerance is apparently lower.
BTW -- My dive today had 3x80's for bailout, a bottle with 12/60, a bottle with 19/40 that I can get on at 220' on the way up, and a 50% which I can switch to at 70'. We were also 3 first downs shallower.
BTW -- My dive today had 3x80's for bailout, a bottle with 12/60, a bottle with 19/40 that I can get on at 220' on the way up, and a 50% which I can switch to at 70'. We were also 3 first downs shallower.
Wookie
Proud to be a Chaos Muppet
Staff member
ScubaBoard Business Sponsor
ScubaBoard Supporter
Scuba Instructor
Wookie
Proud to be a Chaos Muppet
Staff member
ScubaBoard Business Sponsor
ScubaBoard Supporter
Scuba Instructor
tmassey
Contributor
I know it’s been hinted at in this thread as not being an issue, but why isn’t isobaric counter-diffusion an issue, going from 20% nitrogen to 70% nitrogen between the first two? Wouldn’t 21/35 be a more logical jump? And maybe then 50% instead of 80%?
Zero trimix training: I’ve only read the books — and even that only once. Ignore if it’s a dumb question!
- Messages
- 20,561
- Reaction score
- 14,946
- # of dives
- I'm a Fish!
tmassey
Contributor
Again, in my total ignorance, part of my goal was A) getting to less helium faster, and B) putting less pressure on getting to the first switch before I completely run out to gas! Plus the ICD. I’d certainly understand 30/30 as a replacement for EAN32, but it doesn’t take the pressure off that first bottle.
Is ICD one of those “it’s an issue, but not as much as the book makes it to be” kind of issues? Like, say, “1.4 is safe, 1.41 is *not*” kind of things?
OP
I know it’s been hinted at in this thread as not being an issue, but why isn’t isobaric counter-diffusion an issue, going from 20% nitrogen to 70% nitrogen between the first two? Wouldn’t 21/35 be a more logical jump? And maybe then 50% instead of 80%?
Zero trimix *training*: I’ve only read the books — and even that only once. Ignore if it’s a dumb question!
Good question actually. I believe too much importance is placed on maintaining a <0.5 atm change in gas pressure during a switch other than the fact that v-planner and multideco give you alarms when you do it. I have asked the author of those programs to substantiate the reasoning behind it or to point me to any study outlining the danger but never got a satisfactory reply. It is known that the phenomena exists but to what degree is still unclear.
Try plugging the parameters I provided in multideco, then substitute the other gases you mentioned and see the results. If you come up with a better gas profile maybe I'll use yours next time. Remember this is for bailout, ignoring the IBCD warning, use gas volume, total run time and close to even gas consumption between tanks as my main criteria. Also I try to tweak the gas plan to generate an ascent profile as close to the CCR profile as possible. v-planner of multideco makes it easy to compare different scenarios.
Similar threads
