How Much Gas is Enough - Running on Empty (Ainslie)

Just read Ainslie's article in Vol 42 of the NACD Journal, cited in the title to this tread. His story gives an insight into how things can go wrong fast - even for an experienced diver - and the safety buffer generous gas reserves provide as the mind falls into that increasingly numbing state of tunnel vision.

My take from his article is that we need more reserve gas than we may think to handle "real" emergencies. I agree.

Just wanted to say thank you, Andrew Ainslie, for taking the time to share your story, and for giving us one more reason to revisit how safely we may or may not be cave diving.

is this available online?

Sounds like a great article. Does the NACD publish their articles on their website like the CDS does, or only in print?

It'd be great to have access to the knowledge-base of the NACD, even if the articles weren't downloadable, since I don't have the ability to join another great organization right now. If the NACD helped me find a job, however, I'd send them a check tomorrow!

-Jon

Jon and Litehedded, currently the articles are not available online. But I can ask and see if this has been discussed. If you are at REACT this Saturday at Cave Excursions, the NACD booth may have some extra copies to distribute.

Sandy Robinson
pr@safecavediving.com

I believe Andrew mentioned something awhile back about putting his article online after it went to publication.

I haven't gotten my copy yet, but I'm looking forward to it. Maybe all those who constantly argue that 1/3s is enough will finely see that isn't always true.

Never mind! What was I thinking??

This was one scary dive. How to blow through more gas than you ever thought you'd need. And it brings back my old point that I think many people missed years ago when I used to openly discuss why thirds is an oversimplification - compute the minimum that you need, and BRING A LOT MORE!!! - particularly on exploration dives.

I'd like to honour NACD's copyright for a while before posting it online. But a teaser - I had two steel 85's overfilled, several stages... and nearly didn't make it a distance where theoretically one stage should have been enough.

Bill, thanks - I just hope it changes someone else's behaviour in a way that saves their life. It's a little humiliating to admit to this level of incompetence... but each of us has it in us to do the same thing under stress.

Quote:

---

Originally Posted by aainslie

It's a little humiliating to admit to this level of incompetence...

---

I think it took courage to write the article. Especially true given this sport that is so full of critics. Good on you for stepping up and sharing your experience.

As MTV is fond of saying, "Too much is never enough".

Finally got my journal and read the article today. Great article, Andrew! It took courage to put that out there. I hope others will learn from it. I haven't had quite the issue you did, but I've been on dives in which I exited the cave with much less air than is acceptable to me in normal circumstance. No matter how much experience you have in the toughest of situations, the mind will almost always take over, at least for a while. As an instructor I have never taught 1/3s, even in high flow systems. I don't think it's conservative enough. I hope my students keep the same mindset after my classes (I think most do), but I know at least during class, we always incorporate a safer gas management plan. Thanks for putting yourself out there by telling us about the dive!

I agree, I think thirds is not conservative enough at all, even in high flow caves. I think if a real OOA or other very serious emergency happens having counting on the flow to make the exit faster and thus reserving less gas due to that "help" is being unrealistic and overly optimistic about how stuff will most probably go in a real situation.

In no flow caves thirds is definitely not enough and I do not understand why it is an accepted and taught safety margin, I think you can never go wrong with having too much air, but you can very easily go very wrong with having exactly enough.

Wow, I just finished the article. Wow! Great thought provoker on how one would react to the cascade of events.

Since it is close to, or in fact downright impossible to get the NACD journal in the DR is there any way I could pay for and download a copy of it online?

Excellent article Andrew!

A cascade event is something that can happen to any diver. When one thing goes wrong, anything can go wrong.

Thank you Andrew for putting the time to share your experience in a complete and thorough way.

Yes, making it available on-line would be great, even if one had to pay for a copy.

Sorry it took me so long to come back... thanks for all the comments.

Regards,

Andrew

Great article.

Thanks Andrew

Sent from my iPad using Tapatalk

Hey Andrew, I know we talked about this dive a couple of times but I don't remember if we discussed this or not....... D'ya think you'd have drifted off into a side tunnel if the main line was gold braid?

Safe diving,

Rich

Quote:

---

Originally Posted by jlillest

Sounds like a great article. Does the NACD publish their articles on their website like the CDS does, or only in print?

It'd be great to have access to the knowledge-base of the NACD, even if the articles weren't downloadable, since I don't have the ability to join another great organization right now. If the NACD helped me find a job, however, I'd send them a check tomorrow!

-Jon

---

i have a copy of the issue. I can bring it to you next weekend (if I don't forget).

Thanks for sharing, Andrew. Very interesting story. Seems like my worst disasters have come in the Ear. I sucked one tank down because I was struggling with a problem in the current. That just seemed to make everything worse.

Hey Rich,

I think we did chat about it. I think it would have made me realize my error a few critical seconds earlier. That said, it was definitely my idiocy and panic that made me keep going onto a wedged, muddy section long after it was clear i was off the main line.

Andrew,
Great article!! One question Do you think having a buddy who was not panicked, would have helped you remain calmer and more secure?

Hey Ken,

I have mixed feelings about buddies during exploration. Frankly there are not a lot of people willing to go into some of these caves with me. Next, you barely see each other during the most critical parts of the dive as there are extended sections of sidemount only, narrow passage. But, I must say, it would have hugely helped after the emergency started to have someone calming me down.

I'm with you on that, Andrew. There are some passages that I just won't go into unless I'm solo. Trying to dive these passages in a team only increases the risk.

great article man. glad you made it out ok

Great article Andrew, its very nice to share the knowledge after such an event like this. Slow movement, and common sense are key elemnts in survival psychology.

Quote:

---

Originally Posted by phillip1

In no flow caves thirds is definitely not enough and I do not understand why it is an accepted and taught safety margin, I think you can never go wrong with having too much air, but you can very easily go very wrong with having exactly enough.

---

I agree and am not comfortable diving to thirds in most cases.

As to why it's taught, that probably comes down to an over-reliance on accident analysis and statistics. Diving to thirds hasn't killed enough people to consider it completely unsafe and never will. It's just very unlikely. Consider the following scenarios:

1) No flow; dive planned to thirds; one catastrophic gas loss in a two person team at planned max penetration. Even if nobody panics and they share gas, both divers are in deep trouble. The stress and logistics of gas-sharing will probably not allow for a safe exit.

That's the worst case-scenario, however. Additionally, as far as I'm aware, the very few times that actually happened the divers miraculously made it out anyway. After all, there are some mitigating factors: jump and primary reels that might have taken a lot of gas to place; the fact that you might have been surveying, sight-seeing, etc. on the way in; deco bottles somewhere close to the exit, etc...

2) Same as above, but in a three person team. Unless one of them panics or another gas loss occurs, they will be fine.

3) Same as 1), but at around 80% or less of planned max penetration. Again, they will probably get out.

It's common sense that the vast majority of cases of complete gas loss while diving thirds will resemble scenarios 2) and 3). Therefore, it's reasonably unlikely that diving to thirds will kill a lot of divers, which is why it's still taught...

Quote:

---

Originally Posted by Michael Stroeck

I agree and am not comfortable diving to thirds in most cases.

As to why it's taught, that probably comes down to an over-reliance on accident analysis and statistics. Diving to thirds hasn't killed enough people to consider it completely unsafe and never will. It's just very unlikely. Consider the following scenarios:

1) No flow; dive planned to thirds; one catastrophic gas loss in a two person team at planned max penetration. Even if nobody panics and they share gas, both divers are in deep trouble. The stress and logistics of gas-sharing will probably not allow for a safe exit.

That's the worst case-scenario, however. Additionally, as far as I'm aware, the very few times that actually happened the divers miraculously made it out anyway. After all, there are some mitigating factors: jump and primary reels that might have taken a lot of gas to place; the fact that you might have been surveying, sight-seeing, etc. on the way in; deco bottles somewhere close to the exit, etc...

2) Same as above, but in a three person team. Unless one of them panics or another gas loss occurs, they will be fine.

3) Same as 1), but at around 80% or less of planned max penetration. Again, they will probably get out.

It's common sense that the vast majority of cases of complete gas loss while diving thirds will resemble scenarios 2) and 3). Therefore, it's reasonably unlikely that diving to thirds will kill a lot of divers, which is why it's still taught...

---

I agree. Statistically, a total gas failure is extremely rare and a total gas loss failure at max penetration would be an extremely rare subset of an already rare event.

In practice, if the failure occurs a 2-3 hundred psi prior to reaching thirds, it gets all of the benefits of more conservative planning with none of the intent, so in the vast majority of cases where a total gas loss failure has occurred, the dive was not actually done to "thirds" regardless of the intended gas plan.

Also, as you point out, how divers conduct the dive potentially adds safety. Some instructors teach and some divers use a "sight see on the way in" approach as even if you also sight see on the way out, the longer penetration time for a given distance builds in a fudge factor not otherwise present. And this is on top of natural delays due to placing a primary line, jump/gap reels etc that are not pulled on the way out in an emergency.

Additionally, 3 person teams further mitigate the gas loss/reserve issue with thirds that would be present on a two person team, and some instructors suggest additional reserve gas for two person teams.

Finally, rounding down thirds adds some unintended reserve. For example, having 3800 psi in double 95s on the surface just before the dive still results in 1200 psi "thirds" and the 200 psi left over equates to 14 cu ft of additional reserve not factored into the "thirds" calculation. Similarly 3500 psi and 1100 psi thirds results in the same 14 cu ft pad, but results in a slightly greater reserve as a percentage of pentration gas than with 3800 psi.

I think it is roughly analogous to diving with the old US Navy tables. When I started diving they were the only game in town and it was well known that 1) the normative group was not very compatible with recreational divers, 1) the hit rate on square profiles for deco diving and repetitive diving reflected operatioan neccesity and/or on board recompression capability. In light of that, everyone built in fudge factors or operational practices that individually all added small safety margins and cumulatively served to ensure the overall hit rate was acceptably low.

In practice, "thirds" statistically works the same way with a very small incidence of events where divers ran out of gas in circumstances where slightly more conservative gas planning would have made a difference - assuming divers are prudent with it, don't cut corners and recognize when it is clearly not appropriate.

Quote:

---

Originally Posted by DA Aquamaster

Finally, rounding down thirds adds some unintended reserve. For example, having 3800 psi in double 95s on the surface just before the dive still results in 1200 psi "thirds" and the 200 psi left over equates to 14 cu ft of additional reserve not factored into the "thirds" calculation. Similarly 3500 psi and 1100 psi thirds results in the same 14 cu ft pad, but results in a slightly greater reserve as a percentage of pentration gas than with 3800 psi.

---

There's an important point to be made about that. Many divers I know will round down numbers that are not evenly divisible by three. So if they have 220 bar in their tanks, they'll do 210/3=70 bar for penetration. HOWEVER, when they have 210 bar or 240 bar in their tanks, they'll just use that number and divide by three WITHOUT deducting a safety factor afterwards. That makes no sense and I think it's incredibly dumb. You always need to deduct a fudge factor of at least 10 bar, IMHO.

Quote:

---

Originally Posted by Michael Stroeck

There's an important point to be made about that. Many divers I know will round down numbers that are not evenly divisible by three. So if they have 220 bar in their tanks, they'll do 210/3=70 bar for penetration. HOWEVER, when they have 210 bar or 240 bar in their tanks, they'll just use that number and divide by three WITHOUT deducting a safety factor afterwards. That makes no sense and I think it's incredibly dumb. You always need to deduct a fudge factor of at least 10 bar, IMHO.

---

I agree, and on those dives where I really start with 3600 psi (or 3900 psi if the tank monkey is feeling really generous) I tend to turn the dive a couple hunered psi earlier than normal to reflect the loss of the "left over"gas in the orignal thirds calculation.

Is AA's article available online or elsewhere (email, etc.) yet?

Give me one more month, and let me clear it with NACD. I'm in High Springs starting tomorrow so I'll clear itwith Larry and Deb.

Quote:

---

Originally Posted by aainslie

Give me one more month, and let me clear it with NACD. I'm in High Springs starting tomorrow so I'll clear itwith Larry and Deb.

---

Sure, thanks for considering.

nick

It seems to me that taking a stage tank (al80) and dropping it off somewhere along the way might be a good idea. I know this has been talked about ad infinitum, but really, why not just teach it as standard practice? If you dive thirds, and given all the little bits of conservativism along with calculating thirds, why not have a tank waiting for your team somewhere closer than the surface? It would sure make a person feel better to know that plenty of air is waiting ahead.

skip

Quote:

---

Originally Posted by skip

It seems to me that taking a stage tank (al80) and dropping it off somewhere along the way might be a good idea. I know this has been talked about ad infinitum, but really, why not just teach it as standard practice? If you dive thirds, and given all the little bits of conservativism along with calculating thirds, why not have a tank waiting for your team somewhere closer than the surface? It would sure make a person feel better to know that plenty of air is waiting ahead.

skip

---

There are pros and cons. We've done this as a two person team, taking a stage in part way to where things get tight or to a convenient drop point as a means to increase the reserve gas. The only real advantage is one of logistics as you can use the same stage for the whole trip with no need to fill it.

In the extreme you can carry one with the team to max penetration as in essence with 260 ft of back gas it is only about 9 cu ft short of being an entire third all by itself so it and not much more back gas will potentially get an OOA diver out, assuming the exit goes as smoothly as the entrance.

However, from another perspective it makes more sense just to have each diver use a stage on the dive to increase the back gas reserve on the entire dive in addition to having some reserve gas closer to the exit. The disadvantage here is that you end up needing 4 stages to cover two divers making dives per day between fills and it doubles the number of tanks you are hauling around.

However, even if you fall prey to the temptation to just press farther and dive to thirds again, it still reduces the hit of a lost gas scenario as no diver will have a total gas loss as there is still the reserve third left in each stage. Of course that gets us back to arguing about the merits of diving stages to thirds versus half plus 200, but obviously using them this way argues for using the "thirds" approach to spread the reserve gas out a bit more rather than having all the reserve in a diver's backgas.

Skip,

I hope that on longer dives, that's totally the message.

I had 4x the gs necessary to exit. That's equivalent to diving 5ths on OC. And I barely made it out.

Food for thought. On previous trips I dropped a 40 by the jump to the bone room. After the dive I heard someone making cracks about what idiot thought a 40 was any use at that point?

Well, it's a LOT of use if you're running out of gas on your way home after some unexpected detours...

Quote:

---

Originally Posted by aainslie

Skip,

I hope that on longer dives, that's totally the message.

I had 4x the gs necessary to exit. That's equivalent to diving 5ths on OC. And I barely made it out.

Food for thought. On previous trips I dropped a 40 by the jump to the bone room. After the dive I heard someone making cracks about what idiot thought a 40 was any use at that point?

Well, it's a LOT of use if you're running out of gas on your way home after some unexpected detours...

---

Sounds like it takes a lot of gas to replace a redundant brain saying, "Hey, wrong way stupid!" :)

Quote:

---

Originally Posted by jj1987

Sounds like it takes a lot of gas to replace a redundant brain saying, "Hey, wrong way stupid!" :)

---

Careful there mate! I have had buddies going the wrong way, and they wouldn't accept any input. I actually had to tackle one buddy, and drag her in the right direction. She was going upstream in Devil's Eye, on goldline, passing arrows, and still thought it was the way out.

Another buddy was heading down a dead-end passage, and wouldn't believe me that it was wrong. Since it wasn't far to the end, I just followed him to the EOL. Then he gave up, and followed me out.

The "redundant brain" concept is highly overated.

Quote:

---

Originally Posted by jj1987

Sounds like it takes a lot of gas to replace a redundant brain saying, "Hey, wrong way stupid!" :)

---

It could have been said with a bit more grace and tact, but I agree completely.

This incident truly does illustrate the point that while you can bring the reserve gas a buddy would have provided and even clip a couple back up lights on the tank(s), none of that will ever provide the back up of a team mate's brains, eyes and hands.

Marci and I were recently diving a new to us and infrequently travelled by anyone tunnel with very old line with most of it covered in sand and silt. Going in, I was gently pulling it out to ensure continuous line and in the process missed a tee. Marci - doing the redundant brain thing, caught the error and marked the tee. Much later, on the way out she new exactly where we were at and when I noted the her cookie on the tee the gravity of the suituation was apparent. Had I been solo, finding a preveiously unknown and unmarked tee would have casued some confusion and at best would have resulted in some delay while I ensured which way was really out in the very low viz as all the silt stirred up deeper in followed us out. There were other safe guards in place (knowing approximate distances/times, key easily identifyable features in the passage out) so it was not a kajor threat underthose conditions. However had I had an emergency, been under stress and short on gas, that little bit of extra confusion could have created a major delay.

The possible scenarios are interesting - had I taken the wrong passage, then recognized it and reversed course, but missed the (now marked) tee again, I could have ended up going back into the sytem until I again realized the mistake in now very low viz. Making those kinds of errors, especially at any kind of depth could quickly eat through a lot of gas. Personally, I like having Marci alongf as she is avery solid diver and as team members we almost intuitively know what the other is thinking. I also know I am a very good diver with very good cognitive problem solving abilities who handles high levels of stress very well. However I also know I am not perfect and I can use that same intellect to readily envison what could go wrong in most situations. Knowing all that, in my opinion, makes diving solo a poor choice in all but an extremely limited set of circumstances.

------

Forrest is not incorrect that a buddy can add confusion, but that's where backing each other up and properly laying and marking the line is important. In the above case, a poor buddy would have really sucked and added to the delay, but that woudl not have happened sas I make dedicated effort to never dive with a buddy known to be poor and I never take a unknown/untested/untrusted buddy anywhere challenging where that type of confusion could occur.

It's not just having a buddy that matters, but rather having a trusted team member and that is exactly what James is talking about.

Quote:

---

Originally Posted by FW

Careful there mate! I have had buddies going the wrong way, and they wouldn't accept any input. I actually had to tackle one buddy, and drag her in the right direction. She was going upstream in Devil's Eye, on goldline, passing arrows, and still thought it was the way out.

Another buddy was heading down a dead-end passage, and wouldn't believe me that it was wrong. Since it wasn't far to the end, I just followed him to the EOL. Then he gave up, and followed me out.

The "redundant brain" concept is highly overated.

---

+1 @ 100% Thank you!!!

Quote:

---

Originally Posted by DA Aquamaster

It's not just having a buddy that matters, but rather having a trusted team member and that is exactly what James is talking about.

---

I disagree. Dive at Kitty, 3 weeks ago, with my most trusted team member, Bobby. We communicate to play around, I had seen the T to two sinkholes, he had not. So he goes up to our entrance sinkhole (Kitty) then turns back. We surface on the other sinkhole and he says: this is not right, it is not where we came from. I thought he was playing and wanted to check the other sink. He was confused. I did not trust him, said we should go back to the other hole. Apparently I was right.

Everyone can get confused. As much as Bobby is more experienced than me, I doubt him all the time. That's what he has taught me.

Quote:

---

Originally Posted by FW

Careful there mate! I have had buddies going the wrong way, and they wouldn't accept any input. I actually had to tackle one buddy, and drag her in the right direction. She was going upstream in Devil's Eye, on goldline, passing arrows, and still thought it was the way out.

Another buddy was heading down a dead-end passage, and wouldn't believe me that it was wrong. Since it wasn't far to the end, I just followed him to the EOL. Then he gave up, and followed me out.

The "redundant brain" concept is highly overated.

---

or choosing quality buddies is highly underrated?

Quote:

---

Originally Posted by LiteHedded

or choosing quality buddies is highly underrated?

---

I have had some excellent buddies over the years, but most have either quit diving, or passed away :-(

While it would be great to have a regular buddy that you could trust your life with, that is very rare. One of the biggest hurdles is finding someone that is free to go diving when you have the time to go. The second issue if finding someone willing to make the same type of dives you want to do.

Quote:

---

Originally Posted by Xenia

As much as Bobby is more experienced than me, I doubt him all the time. That's what he has taught me.

---

Maybe you better rethink diving with Bobby. :D

Well not really. We are actually talking about the same qualitative issue.

Everyone makes mistakes and that's where the redundant brain becomes important. If everyone were perfect 100% of the time, solo diving would be just fine, but that's not the case and no matter how experienced a diver is, a mistake can be made. When that happens the redundant brain comes into play.

The qualitative difference I am talking about is not perfection but rather a low incidence of mistakes. If you and your buddy are both solid and seldom make a mistake the odds of both of you making the same error and being confused in the same situation are very,very low and the redundancy will work to correct the error.

If someone is a consistent cluster ****, makes serious life threatening mistakes even on a very infrequent basis, or has such limited executive control that they cannot stop, comunicate, consider they may be mistaken, and successfully resolve the issue, then I'm not diving with that person. Or at best I will dive with them in a group of four as two teams of two with that person on the other team.

In this case the important thing is not that Bobby was wrong, but rather than Bobby is not mistaken all that often - the consistenly high performance is what is important, not perfection.

Quote:

---

Originally Posted by FW

While it would be great to have a regular buddy that you could trust your life with, that is very rare.

---

That's where Xenia and I both agree we are very fortunate.

Quote:

---

Originally Posted by FW

I have had some excellent buddies over the years, but most have either quit diving, or passed away :-(

While it would be great to have a regular buddy that you could trust your life with, that is very rare. One of the biggest hurdles is finding someone that is free to go diving when you have the time to go. The second issue if finding someone willing to make the same type of dives you want to do.

---

i totally agree. and I've been quite fortunate in that way.
I think the tough call for a lot of people is just not to go diving. it's a valid option. and the correct one in many circumstances IMO

Quote:

---

Originally Posted by FW

Careful there mate! I have had buddies going the wrong way, and they wouldn't accept any input. I actually had to tackle one buddy, and drag her in the right direction. She was going upstream in Devil's Eye, on goldline, passing arrows, and still thought it was the way out.

Another buddy was heading down a dead-end passage, and wouldn't believe me that it was wrong. Since it wasn't far to the end, I just followed him to the EOL. Then he gave up, and followed me out.

The "redundant brain" concept is highly overated.

---

Sounds like the redundant brain concept worked out quite well for the buddy of yours at the Eye.

Quote:

---

Originally Posted by PfcAJ

Sounds like the redundant brain concept worked out quite well for the buddy of yours at the Eye.

---

Hmm, the question is, did she have one of her own?

Quote:

---

Originally Posted by DA Aquamaster

I agree

---

Holy hell.

Quote:

---

Originally Posted by DA Aquamaster

It could have been said with a bit more grace and tact, but I agree completely.

---

It was meant to stir the pot. Besides, Andrew knows I enjoy picking at him because he's one of the few that will push back with an opposing, yet well thought out viewpoint.

Quote:

---

Originally Posted by Xenia

I disagree. Dive at Kitty, 3 weeks ago, with my most trusted team member, Bobby. We communicate to play around, I had seen the T to two sinkholes, he had not. So he goes up to our entrance sinkhole (Kitty) then turns back. We surface on the other sinkhole and he says: this is not right, it is not where we came from. I thought he was playing and wanted to check the other sink. He was confused. I did not trust him, said we should go back to the other hole. Apparently I was right.

Everyone can get confused. As much as Bobby is more experienced than me, I doubt him all the time. That's what he has taught me.

---

*caugh* I bet someone didn't use a cookie *caugh* ...I've made this same mistake, same cave, and I bet we each messed up for the same reason. I got lazy and it was really close to OW.

Quote:

---

Originally Posted by jj1987

Holy hell.

It was meant to stir the pot. Besides, Andrew knows I enjoy picking at him because he's one of the few that will push back with an opposing, yet well thought out viewpoint.

*caugh* I bet someone didn't use a cookie *caugh* ...I've made this same mistake, same cave, and I bet we each messed up for the same reason. I got lazy and it was really close to OW.

---

Urban Dictionary: Caugh

The sound a gopher makes when it simultaneously coughs and laughs while surrounded by future legal scholars.
www.urbandictionary.com/define.php?term=Caugh -

James, it is true we did not use a cookie on this specific T. We used on the other two Ts. Bobby did not see that T, I did but did not think to use a cookie, because I also noticed that part of the T connected to sinkhole. You have a point though, a cookie would be useful there. I was leading the dive.

Larry, yes we are in agreement. Quality is important. BTW I make mistakes much more often than Bobby... I just like to brag when he makes one because it is rare. ;)

I love diving with him not because we are a couple, but because we are used to each others diving, organization, mistakes, communication, everything is smoother... and he is reliable, I know he won't blow thirds, he knows for sure I won't do this and several other little or bigger things.

I appreciate the experience diving with other people, I try to do this often but if I haven't been in the caves for a while I would rather dive with my regular team mate because I know it is going to be enjoyable.

I just got through doing a week of cave diving with someone I very much respect, and some time early in the week, he made a statement that took me a little aback at first: "If we turn the dive on gas, the dive wasn't planned well enough." I continued to think about that idea throughout the week, and the more I thought about it, the more sense it made. The further I'm going into the caves, the less attractive simple thirds is looking as a gas reserve. It's not that I'm worried about losing it all at once; it's that I'm worried that a mistake way in can raise gas consumption rates to where reserves just don't loom as large as they ought to.

I just joined the NACD, and probably won't get the issue with Andrew's article in it, but knowing what I've read from him in the past, I am sad about that. I am sure the article is honest, and the analysis is cogent and useful.

Lynne, you can read his article next weekend when you're here.

Andrew,
A big thanks for writing this up... I truly feel they are thousands times more to be learned and reinforced in the everyday near misses that never get mentioned vs. the fatalities under the microscope...

I can certainly see how some exploration situations call for solo legs... but I can't help to think some degree of support back in main conduit would have helped stop the snowball...

-Tim

I totally agree with Skip,and I always dive with Al, never use him to extend penetration, and count on him to solve all the what ifs. I also think that is how all full cave divers should be trained. I don't CCR dive but I believe the same bailout considerations should be applied to OC. Is this too conservative? Is there such a thing as too conservative? "The only real emergency is out of air " is not a cliche. IMHO

Huh - sorry I was AWOL on this thread for a while.

James and others on solo- I would love to take anyone willing to go with me on some of these dives. Seriously. But I genuinely cannot. Plus long sections of them are narrow and you cannot communicate much. Last I have to turn the dive early about 30% of the time because of a problem - with 2 divers you end up turning awfully early awfully often.

Exploration just is a sorta solo game for many of us. I now have a side mount rebreather working quite nicely. These things are sorta rare. So I get to play on my own much of the time.

Skip, totally agree. But it takes a lot of self control to do this. When you're repeatedly diving the same section then it's inexcusable not to stash an oh **** stage or two along the way.

Quote:

---

Originally Posted by diverdarren

I always dive with Al, never use him to extend penetration, and count on him to solve all the what ifs.

---

Let me see if I can remember how this goes. Oh, yeah.

"I love AL. He's my favorite buddy. But he's pretty much worthless for anything other than giving you extra gas."

Is there a chance that the article will become available on-line?

Quote:

---

Originally Posted by NEON

Is there a chance that the article will become available on-line?

---

Way back at the beginning of this thread this was posted:

Quote:

---

Originally Posted by aainslie

...I'd like to honour NACD's copyright for a while before posting it online...

---

how long is "a while" when it comes to honouring copyrights? I bet if andrew asked nicely, that the NACD would post the article online at their website. they have done so with other articles in the past.

skip

As promised...

www.asainslie.com/documents

Look for "Rethinking bailout..."

Regards,

Andrew

great article andrew. glad everything came out ok.

You are bloody lucky it wasn't cold on top of all ot that. The closest I have come to getting in trouble was always in cold caves, where numb hands, and brain, added to the problems.

Thank you Andrew!

Thanks for posting the article.

Thank you Andrew!!!!

Quote:

---

Originally Posted by FW

You are bloody lucky it wasn't cold on top of all ot that. The closest I have come to getting in trouble was always in cold caves, where numb hands, and brain, added to the problems.

---

Ican definitely see that happening.

Wow. Scary. Good advice on slowing down and rechecking your reserves.

Another thing occurred to me, Andrew turned fairly early in the planned dive. If he had been another 1000' or so in, it could have been really dicey on bailout, with multiple problems like that.

Do rebreathers generally ever have redundant scrubbers? Since it is hard to know how long it will last, and how much is left, wouldn't it make sense to use 3 smaller independent scrubbers and dive 1/3rds?

Edit: seems that 3 scrubbers each with just enough to get you in and out, and dive each to 50% would be a fairly safe plan.

Quote:

---

Originally Posted by Greenwood_60

Do rebreathers generally ever have redundant scrubbers? Since it is hard to know how long it will last, and how much is left, wouldn't it make sense to use 3 smaller independent scrubbers and dive 1/3rds?

---

Not generally. He didn't run out of scrubber, he broke a hose in a tight tunnel. That would have flooded multiple scrubbers anyway. It is pretty easy to calculate scrubber duration, so you just time when you need to turn.

I finally got to read your story and thanks for sharing it with us. I know that I am no where near your level of cave diving so bear with me on this. I am not trying to pick this apart but why did you continue to drag around, what you believed at the time to be useless, equipment that was creating more drag, additional weight and making restrictions more difficult? We hear about divers recovered from the sea with their weight still attached to them. Sorry, but I feel if my life was in jeopardy I would not be concerned about lugging around a RB and "emptied" tanks.

First I want to say thanks for having the courage to tell everyone about this dive. You are indeed very lucky that the chain of events finally got broken and you made it out safe.
It often seems that when something bad happens it is often a series of decisions that are made upon one seemingly insignifcant one happening and then it spirals out of control.
Although I am not cave certified, hope to start on it in 2011 I have always looked at air as being a commodity I can not do without.

As soon as I started diving I started using a 30 cu.ft. pony on all dives that would give me and anyone else somewhat of a safety net if anything happens. I have been in positions fighting fire where air can go quick. We used to use 30 min rated bottles before switching to 45s and I have seen times where they could be emptied in less than ten minutes and have seen some as low as 5 mins.

Reading this will definetly make me look at gas even way more than just thirds becuase nobody knows will the little gremlins or diver murphy will be with me or anyone else.

Again thanks for sharing this and I hope you never experience this again. I also hope it will prevent some one else from having an accident that can be prevented by just having enough air and taking the time to analyze every problem.

Thanks for the very enlightening article. Obviously, I need to join NACD to get more of the same. I assume those of us with just the Cavern card may join.

Tom

Quote:

---

Originally Posted by TONY CHANEY

.. why did you continue to drag around, what you believed at the time to be useless, equipment that was creating more drag, additional weight and making restrictions more difficult? ...

---

I am sure Andrew will answer, but besides the "head problem" he had, removing equipment can wreack havoc on your buoyancy and trim.

I know that you know far more than me but I thought that trim issues while removing gear is one of the pros of sidemount. Also, it seems that trim was not an issue removing and staging 1 oxygen tank and 2 80's.

Quote:

---

Originally Posted by TONY CHANEY

I know that you know far more than me but I thought that trim issues while removing gear is one of the pros of sidemount. Also, it seems that trim was not an issue removing and staging 1 oxygen tank and 2 80's.

---

You are right about stages and O2, but 85s are pretty heavy, and would greatly change your buoyancy. Depending on what rebreather, it probably would require removing all the other gear to get it off, then you run the risk of floating to the ceiling, and having your tanks on the floor.

FWIW, I would dump any empty stages, but not my side tanks or back/chest mounted rebreather.

Sorry, I wasn't sure exactly how a SM rebreather is mounted. I thought that in sidemount the diver is weighted in order to prevent going to the ceiling while in a no mount configeration. Now the 85's would have been dropped. Simply if you don't need then don't bring it. But I am still learning from divers such as you and Andrew.

Quote:

---

Originally Posted by FW

Not generally. He didn't run out of scrubber, he broke a hose in a tight tunnel. That would have flooded multiple scrubbers anyway. It is pretty easy to calculate scrubber duration, so you just time when you need to turn.

---

Ideally, it would be something that would be sealed until it was needed. If it is easy to calculate duration, then 2 should be sufficient, and dive each to 1/3rds. Seems this would lend well to a SM RB config too.

Quote:

---

Originally Posted by Greenwood_60

Ideally, it would be something that would be sealed until it was needed. If it is easy to calculate duration, then 2 should be sufficient, and dive each to 1/3rds. Seems this would lend well to a SM RB config too.

---

Simplicity is the key. Rebreathers are complicated enough, without having to switch scrubbers during a dive.

Quote:

---

Originally Posted by TONY CHANEY

Sorry, I wasn't sure exactly how a SM rebreather is mounted. I thought that in sidemount the diver is weighted in order to prevent going to the ceiling while in a no mount configeration. Now the 85's would have been dropped. Simply if you don't need then don't bring it. But I am still learning from divers such as you and Andrew.

---

If you plan to go no-mount, you can weight yourself for no-mount, but I think Andrew was just using the 85s for bailout. As for how sidemount breathers attach, there are very few that have the counterlungs in the same container as the scrubber. Those can be removed fairly easily.

IIRC, Andrew's is actually a modified backmount, and he was wearing the counterlungs on his shoulders, under all the other gear.

I think the biggest issue here was time-pressure messing with his head, and he wasn't thinking clearly.

As always, thanks FW. I figure that Andrew would be able to shed so light on this. I would really need to see it in order to get a picture in my mind.

Quote:

---

Originally Posted by Tom Kreider

Thanks for the very enlightening article. Obviously, I need to join NACD to get more of the same. I assume those of us with just the Cavern card may join.

Tom

---

I believe anyone can join (no cert required) but you must be "full cave" (or equivalent) to have voting privileges.

Here is the membership application on NACD's website.

Yes, anyone can join. You don't even have to be cavern trained/certified, or a diver for that matter! :D

Forrest,

Thanks for providing pretty accurate answers there! The SM tanks were steel and i didnt want to dump them for buoyancy reasons. While the rebreather is theoretically removable, it's a PITA to do so, and in fact in my latest config it cannot be removed. However in my latest version I hae also gone entirely to Al80's in order to be able to dump more cylinders safely. I now move through restrictions pushing one 80 ahead, bringing 1 behind between my legs, with the RB sm on the left. Allows one to pass through pretty small spaces.

Andrew and Forrest thanks for clearing this up for me.

Quote:

---

Originally Posted by aainslie

I now move through restrictions pushing one 80 ahead, bringing 1 behind between my legs.

---

Andrew,

I assume you're clipping off the 2nd tank to a clip on your crotch strap, is this the same one you're using for scooter attachment?

How are you parking regs so they don't get bumped & scraped when the tank is between your legs?

I have yet to attempt any restrictions, but planning several future dives in VA caves, I'm sure I'll eventually come across something where this might come in handy.

Thanks,
-Jon

Quote:

---

Originally Posted by aainslie

Forrest,

Thanks for providing pretty accurate answers there!

---

He's smarter than he looks :)

http://www.scubaboard.com/gallery/da...ntaForrest.jpg

Quote:

---

Originally Posted by SuPrBuGmAn

He's smarter than he looks :)

---

Ho, Ho, Ho!

Yeah, it was leftover from last year :/ I need to do better.

Very funny. Try "goelfyourself" would make a good one.

Great article Andrew. Thanks for being upfront and sharing your experience. This is the sort of incident all cave divers can learn from.

Tony

Thank you Andrew for making this article available. Good read with a few things to keep in the forefront of planning...
Don

Quote:

---

Originally Posted by jlillest

Andrew,

I assume you're clipping off the 2nd tank to a clip on your crotch strap, is this the same one you're using for scooter attachment?

How are you parking regs so they don't get bumped & scraped when the tank is between your legs?

I have yet to attempt any restrictions, but planning several future dives in VA caves, I'm sure I'll eventually come across something where this might come in handy.

Thanks,
-Jon

---

Sorry, just saw this. I have a ring high on my butt, a lot of people have one there. The tank hooks in there. the reg's pretty well protected by my legs. Although to be honest, going through rrestritions, EVERYTHING gets bumped and scraped almost by definition...