Do you dive 1/3s?

[RN]

With the number of threads being started based on comments in existing threads, I figured I'd beat everyone to it here...

I rarely, if ever, dive 1/3s and I also teach that I don't think it's conservative enough for a 2 person team. I'll explain my reasoning later.

What about you? Do you dive 1/3s? Why or why not?

[J_glenn06]

It seems That the latest threads have sparked up alot

http://www.cavediver.net/forum/showthread.php?t=12848

[ssmdive]

Depends. Normally I have a team of two and we have a dive plan, and if we make it to our planned point before 3ds we either turn and go out slowly, or poke around till we hit 3rds and then exit.

Done 3rds a bunch on the main line at Ginnie, knowing the flow will expedite our exit.

But for a low/no flow max penetration... I'd rather have a team of 3. Still in most cases the idea of thirds does not bother me. But I will wait for tour opinion with interest.

[tflaris]

Yes. Unless conditions dicate otherwise

[SuPrBuGmAn]

Depends on the flow, number in the team, and if its a system I'm very familiar with dictates an easy exit.

[sskasser]

It's a starting point for simplicity's sake. Then I take into consideration: flow, team members (quantity and quality), nastiness of the cave, familiarity with the cave, stashed gas, and gut feelings. Based on these, I then decide how much more conservatively than thirds I want to dive.

[sam]

I dive solo even if in a team. So it really depends on the cave. I also dive sidemount and normally even carry a 40 as a buddy. So yes I dive 1/3's unless normal cave requirements dictate otherwise...

[jj1987]

Flow and silt change things a lot more for me than the number of team members. I usually dive 1/3rds, but there's a few areas I back off.

[Michael Stroeck]

I very much prefer not to. I'm a very new cave diver, but I'm starting to believe that thirds PLUS at least a staged 40 (or 80, depending on depth) a few hundred feet in is the minimum for two-man dives without flow.

[FW]

About the only place I dive 3rds is Devil's Eye. I add 50 to 100 psi for each thing that could cause delays, like:
Low flow (even more for a syphon)
Silt
Each restriction
Unfamiliar buddies (especially if they have high SAC rates)

[MichaelBaranowski]

I dive 1/6th cause I am only a intro-diver.

[skip]

I always determine thirds, then turn the dive a 100-300 psi before thirds. We dive low/no flow caves, poor viz (3-10ft), silty, small. Some say I should be diving fourths or whatnot, but I don't...unless 300 psi above thirds = fourths! oh wait....it is! anyway, number of team members does not matter to me, I just like to have that little bit of extra safety even if it's mostly psychological.

may need another thread on this one, but when I turn to exit, I don't mess around, but go home as straight-away as possible. The sight-seeing takes place on the way in (unless there's a mission that begins further in). Wonder how many others do the same, or lolly-gag instead on the way out?

skip

[DA Aquamaster]

About the only place I dive 3rds is Devil's Eye. I add 50 to 100 psi for each thing that could cause delays, like:
Low flow (even more for a syphon)
Silt
Each restriction
Unfamiliar buddies (especially if they have high SAC rates)I put a great deal of weight in comments made my someone with this level of epxerience and the perspective that comes from that many decades of cave diving.

I selected a full cave instructor in large part due to the same criteria as well as due to the fact that that particular instructor has never had a former student die in a cave despite teaching for a very long time.

Nothing predicts success like past success.

[RN]

I'm a little surprised at the number of people that dive 1/3s regardless of the number of team members.

I was taught diving 1/3s was acceptable and did that for some time. The more I thought about it, the more it didn't make sense to me, though. While it basically protects against a very unlikely situation, it's still a possible situation. Here's the scenario:

Diver A and B are diving same size cylinders, filled to the same pressure and have the same air consumption rate. This isn't actually too far fetched so far. My wife and I both dive 95s, we fill at the same time, and our air consumption is within 100 psi of each other at the end of the dive.

Here's the part that's not that likely:

We both hit 1/3s at the same time and one of us has a complete gas loss. It takes us a minute or so to do the OOA and get set up. Consumption might be a little higher on the exit.

If we both started with 3600 and turned at 2400, we now have 1200 a piece to make it out of the cave. We just spent about a minute getting into an air share. The likelihood of us having enough air to get out is not that great.

I realize the air loss has to happen at a particular point for this scenario, but no one can guarantee it won't happen there.

Cutting back your turn pressure by 100 psi doesn't really take much air or penetration distance from your dive, yet it gives you 300 psi more reserve than if you don't.

Start with 3600 psi. 1/3s is 1200 or 2400 psi turn pressure. Make that 2500 psi instead. That's 1100 psi penetration, 1100 psi exit, and 1100 psi for emergencies - 3300 psi. 300 psi gets added to reserve to deal with the gas switch and possible increase in consumption.

Add 200 psi back and you have 600 psi extra for reserve.

In high flow, I always add 100 psi back in. In low flow I add 200 psi back. When solo I add 300 psi (1/4s). If I need the extra gas to do the dive I just add a stage bottle. 100-200 psi isn't going to make that much of a difference. 200 psi in a set of 95s is about 14 cf. With a .35-.4 RMV, that's only about 8-10 minutes at 100 ffw. Is it really worth it?

[LiteHedded]

I do for the most part
total loss of backgas at max penetration is a boogeyman and just doesn't happen IMO

this will change as rock bottom gas requirements go up or in a siphon of course

[sskasser]

I'm a little surprised at the number of people that dive 1/3s regardless of the number of team members.

I was taught diving 1/3s was acceptable and did that for some time. The more I thought about it, the more it didn't make sense to me, though. While it basically protects against a very unlikely situation, it's still a possible situation. Here's the scenario:

Diver A and B are diving same size cylinders, filled to the same pressure and have the same air consumption rate. This isn't actually too far fetched so far. My wife and I both dive 95s, we fill at the same time, and our air consumption is within 100 psi of each other at the end of the dive.

Here's the part that's not that likely:

We both hit 1/3s at the same time and one of us has a complete gas loss. It takes us a minute or so to do the OOA and get set up. Consumption might be a little higher on the exit.

If we both started with 3600 and turned at 2400, we now have 1200 a piece to make it out of the cave. We just spent about a minute getting into an air share. The likelihood of us having enough air to get out is not that great.

I realize the air loss has to happen at a particular point for this scenario, but no one can guarantee it won't happen there.

Cutting back your turn pressure by 100 psi doesn't really take much air or penetration distance from your dive, yet it gives you 300 psi more reserve than if you don't.

Start with 3600 psi. 1/3s is 1200 or 2400 psi turn pressure. Make that 2500 psi instead. That's 1100 psi penetration, 1100 psi exit, and 1100 psi for emergencies - 3300 psi. 300 psi gets added to reserve to deal with the gas switch and possible increase in consumption.

Add 200 psi back and you have 600 psi extra for reserve.

In high flow, I always add 100 psi back in. In low flow I add 200 psi back. When solo I add 300 psi (1/4s). If I need the extra gas to do the dive I just add a stage bottle. 100-200 psi isn't going to make that much of a difference. 200 psi in a set of 95s is about 14 cf. With a .35-.4 RMV, that's only about 8-10 minutes at 100 ffw. Is it really worth it?

Good points, Rob, plus, how about if one's gauge is a little off or one's reg won't suck that last 100psi out of the tank? This method definitely would be a big benefit to that diver!

[ianr33]

Here's the part that's not that likely:

We both hit 1/3s at the same time and one of us has a complete gas loss.

How does one of you have a complete gas loss diving sidemount?

I'm a pretty new cave diver. For what its worth I'm much happier reserving more than 1/3rds in low/no flow. Thats more to do with a slow exit due to silting/whatever rather than a complete gas loss though. (I dive sidemount)

[sskasser]

How does one of you have a complete gas loss diving sidemount?



By TOTALLY pissing off Murphy! :yawinkle:

[MORGAN]

I usually turn at 200 psi above thirds.

The only time I go all the way down to thirds is in cave which is A) familiar, B) has strong outflow and C) has no significant restrictions between me and the exit.

Mike

[alias]

I can’t really answer the poll yet as I just got the license to dive to thirds last month. What I can say is that after diving sixths, diving to thirds made me feel like I was sucking the tanks so dry, lol. I only got experience of thirds in high flow, and judging from my gut feeling, I won’t be diving to thirds with my buddy any time soon in lower flow.



may need another thread on this one, but when I turn to exit, I don't mess around, but go home as straight-away as possible. The sight-seeing takes place on the way in (unless there's a mission that begins further in). Wonder how many others do the same, or lolly-gag instead on the way out?


I wanted to comment on this. IMHO this is one very negative habit that diving to sixths may teach beginner cave divers. Having such a huge reserve, it sure has made me slowpoke on exit, and I have had to pay special attention to correct this after I realized what was happening.

Having such a limit on entry can surely backfire if divers shoot like bat out of hell into the cave and then use double or triple the time/gas to meander out. I understand the limit was set as a safety precaution but the limit on penetration may backfire if it fosters bad future habits.

[LCF]

Well, I mostly dive in Mexico, where flow almost never is enough to help you. I was taught to do all the sightseeing on the way in; your only task on the way out is to GET out.

On the other hand, obviously, the closer you get to the exit, the more gas "cushion" you're carrying, and the less important keeping up a faster pace than your entry becomes. On 6ths, we hurried, because if we got out with enough gas, we could do another dive on the same set of tanks. On thirds, there's no point; you aren't going to use those tanks again. So I'll lollygag and sightsee on the way out, once we have passed about the halfway mark.

[murfef]

By TOTALLY pissing off Murphy! :yawinkle:


That's right, you don't want to piss me off!!:mad:

[DA Aquamaster]

I wanted to comment on this. IMHO this is one very negative habit that diving to sixths may teach beginner cave divers. Having such a huge reserve, it sure has made me slowpoke on exit, and I have had to pay special attention to correct this after I realized what was happening.

Having such a limit on entry can surely backfire if divers shoot like bat out of hell into the cave and then use double or triple the time/gas to meander out. I understand the limit was set as a safety precaution but the limit on penetration may backfire if it fosters bad future habits.I agree. A related issue is that trying to get more penetration on 1/6ths can push divers to skip breathe and take other less than ideal approaches to increase penetration without breaking 1/6ths. That bad habit, and the related elevated CO2 levelsand resulting increased narosis and increased suceptibility to ox tox then follow them through the rest of their cave diving career. A culture surrounding an ideal of having a SAC rate and self imposed pressure by some divers not to be the guy who turns the dive on gas tend to aggravate the problem.

In practical terms, skip breathing to push more feet out of a given amount of gas can potentially leave the diver in oxygen debt, and/or feeling less motivated to stretch the gas on exit, greatly increasing the potential to get yourself in trouble on exit in a gas emergency.

[Mike Edmonston]

I used to reserve gas by diving 100 - 200 PSI before thirds and turning at that point. I used that routine in High flow and no flow systems alike. Within the last year or so, I began bringing in a stage as extra reserve for the "just in case" scenario. In large passages (Peacock etc..) I carry it with me the entire dive. In higher flow systems( Devils, LR etc...) I'll drop it at about the 1000' mark and continue until I reach thirds.

It's worked for me really well, but it seems to draw flak from some divers who tell me that I shouldn't bring down any gas that I'm not planning to use, as that is poor gas management! Uhhh... What????

I then kindly asked them if they were diving 1/2's because thirds would leave them with extra gas that they didn't use. They said something to me in Swedish, then dove off! Oh well, I'll take my stage with me anyway.

As a side note, if I am diving a new or unfamiliar system, or am teaching a class, I will usually have a AL40 strapped to me that I can quickly give to a student or use myself if a giant cave monster eats my manifold and spits out my tank neck O-rings.

I still won't break thirds though.

YMMV...

Cheers

[DA Aquamaster]

Within the last year or so, I began bringing in a stage as extra reserve for the "just in case" scenario. In large passages (Peacock etc..) I carry it with me the entire dive. In higher flow systems( Devils, LR etc...) I'll drop it at about the 1000' mark and continue until I reach thirds.

It's worked for me really well, but it seems to draw flak from some divers who tell me that I shouldn't bring down any gas that I'm not planning to use, as that is poor gas management! Uhhh... What????I started doing the same thing on the advice of my full cave instructor who pointed out the pitfalls of a two person team combined with a very good SAC rate and potentially long penetrations on just back gas. It made sense to me.

However I hear exactly the same argument you do regarding the gas planning "flaw" in carrying excess gas I don't plan to use.

I see and understand their perspective for the types of dives they either do, or plan to do in the future, or just learned from divers/instructors who may actually do that type of diving. But it really comes down to a matter of different divers having different priorities.

Given the dives me and my usual team mate do, peak efficiency is not the first priority and the small additional effort in carrying an "extra" stage is worth the benefit from my perspective. On the course of an entire dive, on average, I'll use 200 psi more gas carrying a stage than not, so there is a measurable impact on efficiency cmpared to not carrying a stage at all. But at 45, I am past the point where pushing the envelope is still fun, so I'd rather stock up on excess gas and carry a stage to substitue for what amounts to very close to a third person's reserve gas when diving on a two person team.

Oddly enough, if I and my team mate were to burn a stage to half plus 200 and keep all the reserve in back gas, that becomes more acceptable to some of the critics. However, their change in attitude ignores the fact that the floaty less than full stage creates more drag for a significant portion of the dive and incurs more drag and gas penalty than just carrying a full one. It also ignores the more complicated logitics required with the need to load four stages in the vehicle each morning of a two dive day and refill them each night, rather than just one safety bottle that stays full all week.

There is also a degree of irony that some of the same critics of carrying "excess" gas will talk and post about diving stages and never touching the back gas, but may do it on comparatively short dives with only 2-3 stages. With two stages and 144 cu ft used, 260 cu ft of back gas carried in reserve provides a whopping 180% reserve. With three stages and 216 cu ft used, 260 cu ft of back gas carried in reserve still provides an impressive 120% reserve.

Instead of diving 2 stages and not touching the backgas, you could do the same dive with just your 260 cu ft of back gas and not carry stages at all. You'd still have 116 cu ft in reserve, or 44% of the total gas (11% better than thirds) with no need to carry a stage at all.

And, in terms of carrying a stage as a safety, diving 260 cu ft of back gas to thirds uses 173 cu ft total, leaving 87 cu ft in reserve. When you add another 77 cu ft in a safety bottle, you get 164 cu ft in reserve - a 94% reserve.

The critics' logic seems to run off the rails when that 94% reserve is viewed as "excessive" and "inefficent" as it requires carrying a single stage you don't plan to use. However carrying two or three stages and not touching back gas that amounts to a 120-180% reserve is considered ok. Go figure.

[Slüdge]

I haven't breathed backgas in several years. It started back when I had to PP blend nitrox and I hated coming home from a dive weekend and draining four sets of doubles from over 2,000psi.

I had started carrying a buddy bottle for various reasons and I decided to go the "breathe a stage only" route. I can get over an hour from an AL80, and it was much easier to drain four stages from around 400psi each. So on a typical scooter dive at JB I'll carry almost 300 cubic feet in and breathe around 70 cubic feet. If someone doesn't like that, tough. I like having lots and lots of reserve.

[FW]

I haven't breathed backgas in several years. It started back when I had to PP blend nitrox and I hated coming home from a dive weekend and draining four sets of doubles from over 2,000psi.

I had started carrying a buddy bottle for various reasons and I decided to go the "breathe a stage only" route. I can get over an hour from an AL80, and it was much easier to drain four stages from around 400psi each. So on a typical scooter dive at JB I'll carry almost 300 cubic feet in and breathe around 70 cubic feet. If someone doesn't like that, tough. I like having lots and lots of reserve.
There are actually a *lot* of cavedivers that use that technique.

[FW]

I'm a little surprised at the number of people that dive 1/3s regardless of the number of team members.
Looking back at the poll, I see why is seems so skewed. I suspect some people think "I never dive thirds" means, "I bust 3rds all the time". That is actually opposite of what you seem to be implying.

The same is true of "I always dive thirds, regardless..." They overlook the two vs three diver team aspect.

If you want to see a really skewed poll, look at the "virgin passage" poll. It is pretty hard to believe that over 40% of the divers on this forum have actually laid line in unexplored caves.
:rollguy

[DA Aquamaster]

I haven't breathed backgas in several years. It started back when I had to PP blend nitrox and I hated coming home from a dive weekend and draining four sets of doubles from over 2,000psi.

I had started carrying a buddy bottle for various reasons and I decided to go the "breathe a stage only" route. I can get over an hour from an AL80, and it was much easier to drain four stages from around 400psi each. So on a typical scooter dive at JB I'll carry almost 300 cubic feet in and breathe around 70 cubic feet. If someone doesn't like that, tough. I like having lots and lots of reserve.That makes perfect sense and I did the same basic thing when I lived in an area and era where air was all you could get. DIY PP fills transfilling 02 into an empty stage was much easier and more efficient than into a set of doubles with 1200 psi left in them.

At this point however, with our particular travel logisitcs and available fill issues the back gas with safety bottle approach is logisitcally more efficient. I'm still assessing what sidemount diving will do to this.

I don't object to the "backgas only" practice at all, just to people being judgmental of how other people choose to carry/manage their gas based on a very narrow point of view based on a "you should not carry gas you don't intend to use" principle.


Looking back at the poll, I see why is seems so skewed. I suspect some people think "I never dive thirds" means, "I bust 3rds all the time". That is actually opposite of what you seem to be implying.

The same is true of "I always dive thirds, regardless..." They overlook the two vs three diver team aspect.Exactly. I'll consider thirds much more often in a 3 person team than in a 2 person team. Realistically the difference is that we'll often do thirds in a 3 person team, and may also do thirds on the same dive in a two person team - but with a safety bottle, so it's not entirely correct to call it "thirds".

Then as mentioned previopusly, the use of "stage only" gas plans often amounts to a very generous reserve carried in back gas.

Cake comes in more flavors than just chocolate.

[LiteHedded]

I started doing the same thing on the advice of my full cave instructor who pointed out the pitfalls of a two person team combined with a very good SAC rate and potentially long penetrations on just back gas. It made sense to me.

However I hear exactly the same argument you do regarding the gas planning "flaw" in carrying excess gas I don't plan to use.

I see and understand their perspective for the types of dives they either do, or plan to do in the future, or just learned from divers/instructors who may actually do that type of diving. But it really comes down to a matter of different divers having different priorities.

Given the dives me and my usual team mate do, peak efficiency is not the first priority and the small additional effort in carrying an "extra" stage is worth the benefit from my perspective. On the course of an entire dive, on average, I'll use 200 psi more gas carrying a stage than not, so there is a measurable impact on efficiency cmpared to not carrying a stage at all. But at 45, I am past the point where pushing the envelope is still fun, so I'd rather stock up on excess gas and carry a stage to substitue for what amounts to very close to a third person's reserve gas when diving on a two person team.

Oddly enough, if I and my team mate were to burn a stage to half plus 200 and keep all the reserve in back gas, that becomes more acceptable to some of the critics. However, their change in attitude ignores the fact that the floaty less than full stage creates more drag for a significant portion of the dive and incurs more drag and gas penalty than just carrying a full one. It also ignores the more complicated logitics required with the need to load four stages in the vehicle each morning of a two dive day and refill them each night, rather than just one safety bottle that stays full all week.

There is also a degree of irony that some of the same critics of carrying "excess" gas will talk and post about diving stages and never touching the back gas, but may do it on comparatively short dives with only 2-3 stages. With two stages and 144 cu ft used, 260 cu ft of back gas carried in reserve provides a whopping 180% reserve. With three stages and 216 cu ft used, 260 cu ft of back gas carried in reserve still provides an impressive 120% reserve.

Instead of diving 2 stages and not touching the backgas, you could do the same dive with just your 260 cu ft of back gas and not carry stages at all. You'd still have 116 cu ft in reserve, or 44% of the total gas (11% better than thirds) with no need to carry a stage at all.

And, in terms of carrying a stage as a safety, diving 260 cu ft of back gas to thirds uses 173 cu ft total, leaving 87 cu ft in reserve. When you add another 77 cu ft in a safety bottle, you get 164 cu ft in reserve - a 94% reserve.

The critics' logic seems to run off the rails when that 94% reserve is viewed as "excessive" and "inefficent" as it requires carrying a single stage you don't plan to use. However carrying two or three stages and not touching back gas that amounts to a 120-180% reserve is considered ok. Go figure.
you're not comparing apples to apples here. one is essentially a pony bottle to give the diver a warm and fuzzy feeling. the other is extra gas that's needed to extend your penetration into the cave.

ignoring the fact that you'll be dropping it, how does a less than full stage create more drag?
it's going to be close to neutral, requiring zero gas in your wing and it will float up behind your arm in the slipstream.

but I say if carrying a safety bottle with you on all dives makes you feel safer, go for it.

also, you mention not touching backgas. we do this on scooter dives, not swimming dives, where the gas planning is a tad different and reserves go through the roof rather quickly.

[phillip1]

I never dive thirds I don't think it's safe, I also have only dove one cave with a lot of flow we found here recently, now I had read on the board about how you can safely dive to thirds and count on the flow to push you out.
Having never dove a flow cave I did not really know what to expect, as I said above we found a cave with flow here (first DR full on spring). Now I think that to count on the flow for a nice short uneventful exit is really an unsafe way of thinking.
Yes we did a bunch of long penetrations and yes the exits were waaay faster, but there still is a ton of stuff that can go wrong.
I actually think that is is more dangerous in a flow cave as the flow could transport you far away from the line in a flash and you can really get into a bad lost line situation.
I think you can get more tangled in the line as the flow will push you more into it etc..
So I think that thirds is not enough in a flow cave, in my opinion don't count on flow to help, make sure you have more than enough air.
Now mind you we are in a unexplored cave so we are super conservative in air planing but no matter were I dive be it exploration or not I never get to thirds I do not think it is conservative enough and especially not in no flow caves, in a no flow situation if your buddy looses his/her air at max penetration and you were diving thirds you are dead, I do not understand why training agencies teach the rule of thirds in no flow caves it is a really unsafe air planing I think, maybe an acceptable risk in flow caves (although I don't agree) but in no flow it is really unsafe.

[LiteHedded]

I never dive thirds I don't think it's safe, I also have only dove one cave with a lot of flow we found here recently, now I had read on the board about how you can safely dive to thirds and count on the flow to push you out.
Having never dove a flow cave I did not really know what to expect, as I said above we found a cave with flow here (first DR full on spring). Now I think that to count on the flow for a nice short uneventful exit is really an unsafe way of thinking.
Yes we did a bunch of long penetrations and yes the exits were waaay faster, but there still is a ton of stuff that can go wrong.
I actually think that is is more dangerous in a flow cave as the flow could transport you far away from the line in a flash and you can really get into a bad lost line situation.
I think you can get more tangled in the line as the flow will push you more into it etc..
So I think that thirds is not enough in a flow cave, in my opinion don't count on flow to help, make sure you have more than enough air.
Now mind you we are in a unexplored cave so we are super conservative in air planing but no matter were I dive be it exploration or not I never get to thirds I do not think it is conservative enough and especially not in no flow caves, in a no flow situation if your buddy looses his/her air at max penetration and you were diving thirds you are dead, I do not understand why training agencies teach the rule of thirds in no flow caves it is a really unsafe air planing I think, maybe an acceptable risk in flow caves (although I don't agree) but in no flow it is really unsafe.

but that just doesn't happen

[phillip1]

it could definitely happen.

Anyway to each his own, I do not dive with people who are not conservative, or who are willing to cut corners.
There is a BIG difference between the willingness to accept certain risks beyond your control like having to back out of an unexplored tight passage if it does not go and all the related risks with that, line entanglement getting stuck etc..
and the willingness or complacencyness (is that a word?) to accept some really dumb risks such as not planning more than enough air, visual jumps, no permanent guideline to OW etc..
For me and the dive buddies I dive with, we all know there are inherent risks in cave diving even more so with exploration, when we plan our dives we do everything we can to reduce those risks and have our bases covered as best we can.

[LiteHedded]

certain situations dictate dialing back the turn pressure. sure. you've listed some valid reasons for doing so.
but planning for a complete loss of backgas at max penetration is a tad much IMO
it's going to take two simultaneous failures right when you hit turn pressure to lose all of your gas
thirds is enough for me in most systems in a lot of situations. and I think accident analysis bears this out

[phillip1]

Ok in sidemount or independents, although I don't agree I understand your point, a total gas loss will be extremely unlikely (has that even ever happened?) but in BM, it is very possible.
Why not aply that extra measure of conservatism to diving SM and making it that much safer, if anything you have an even greater gas reserve should any of the myriad of other possible problems arise.
I think that an extra 10-15mins of diving time/penetration is not worth the huge safety margin of not diving to thirds.

[DA Aquamaster]

you're not comparing apples to apples here. one is essentially a pony bottle to give the diver a warm and fuzzy feeling. the other is extra gas that's needed to extend your penetration into the cave.

ignoring the fact that you'll be dropping it, how does a less than full stage create more drag?
it's going to be close to neutral, requiring zero gas in your wing and it will float up behind your arm in the slipstream.

but I say if carrying a safety bottle with you on all dives makes you feel safer, go for it.

also, you mention not touching backgas. we do this on scooter dives, not swimming dives, where the gas planning is a tad different and reserves go through the roof rather quickly.I don't disagree with 90% of what you are saying. The point was exactly that it is NOT an apples to apples comparison - different approaches are used for different purposes and I am totally ok with that.

I'm just pointing out that carrying a stage on a two person team to pad the reserve gets critisized (I think the wording in this case is "essentially a pony bottle to give the diver a warm and fuzzy feeling"). In contrast, breathing the stage and carrying the extra reserve in backgas would usually meet with more approval - but complicates the logistics of the average cave diving day. That suggests a bit of intolerance on the part of some divers who can't or won't consider another perspective. It more or less is like always presuming an "apple" would work better, even though another diver may want to make "orange" juice.

I do however have to disagree with the bolded portion of your comment above. I know it is a very commonly held belief taught by many, many instructors, but you have to have a very liberal view of a diver's "slipstream" to buy that argument and I have enough time in aerodynamics classes and wind tunnels to have a great deal of trouble with that concept. When you look at the average empty stage on the average stage rig, it will be tail light and floating nearly vertically in the water - well above the diver and certainly not in their "slipstream" in any meaningful sense of the word.

To be fair, when scootering, an empty stage lays down a bit better, but it is the water flow on the stage that pushes it down and that energy required to push it down constitutes "drag".

I have noted some sidemount rigging techniques that will help keep the tail down on an empty stage, and bottom mounting the empty stage under a sidemount tank also does a great job, but I have yet to see very many swimming backmount divers with an empty stage at less than a 45 degree angle.

So to answer the question you pose, I do feel a full stage offers lower drag as it maintains a lower drag profile in the water as long as you have the stage properly rigged.

[DA Aquamaster]

Ok in sidemount or independents, although I don't agree I understand your point, a total gas loss will be extremely unlikely (has that even ever happened?) but in BM, it is very possible.I am not understanding the logic of a total failure being "very possible" in backmount - at least with an isolator manifold. I've never actually heard of one, so it's more of a theoretical multiple failure possiblity than a legitamate concern.


certain situations dictate dialing back the turn pressure. sure. you've listed some valid reasons for doing so.
but planning for a complete loss of backgas at max penetration is a tad much IMO
it's going to take two simultaneous failures right when you hit turn pressure to lose all of your gas
thirds is enough for me in most systems in a lot of situations. and I think accident analysis bears this outI agree that you'd have to have a neck o-ring or burst disk failure at the turn point and then also be unable to isolate the tanks, or have the reg on the remaining post "fail" to have a total gas loss. And that is indeed extremely unlikely. As long as you have a team member with a "third" in reserve, and a fair amount of gas remaining after a failure, you will still be golden.

On the other hand, I like being fat on gas and I like not having to worry about absolutely needing to exit as fast as I entered, especially if the failure results in a silt out, the team behind you rototilled the cave, etc, etc, etc. Nobody ever died from having too much gas in reserve, but having too little can kill you.

It's not a case where either perspective is right or wrong, they are just different perspectives based on different goals and priorities. What is true regardless of perspective is that thirds has worked pretty well over the last few decades to keep cave divers coming out alive and is arguably a very good way to achieve a balance between the need to have an adequate reserve and not getting extremely excessive in terms of planning for multiple failures.

[jj1987]

I have noted some sidemount rigging techniques that will help keep the tail down on an empty stage, and bottom mounting the empty stage under a sidemount tank also does a great job, but I have yet to see very many swimming backmount divers with an empty stage at less than a 45 degree angle.
Clip the bolt snap to your crotch strap instead of SPG dring and it's a non issue (not that's an issue on your SPG dring either, but I'll play along...).

I'm still confused as to why anyone would leave their safety gas in the front of the cave where it's least likely to be needed, but then again we don't seem to see eye to eye on risk analysis, as I wouldn't bring a pony bottle (:yawinkle:) for the grand traverse

[LiteHedded]

agreed. if you don't like how the empty stage rides clip if off to the crotch.
but to float that full stage you're going to have to add gas to the wing. that WILL create more drag
don't get me wrong. carrying extra gas is super. be as conservative as you want to be. squirrely, virgin cave is a great time to get conservative.

but losing all your gas at max penetration is just silliness. and if you can't efficiently shut down a post or isolate your tanks you should be back there to begin with.

[LiteHedded]

of course now that I've said this my manifold will explode just as I'm thumbing the next dive :D

[SuPrBuGmAn]

I haven't seen that many stages pointing straight up, or even at a 45. I think most people have enough sense to clip them.

Maybe on a leash...

[phillip1]

[QUOTE=DA Aquamaster;104159]I am not understanding the logic of a total failure being "very possible" in backmount - at least with an isolator manifold. I've never actually heard of one, so it's more of a theoretical multiple failure possiblity than a legitamate concern.

Although highly unlikely it is possible so why not have all your bases covered and plan for that? I thought that is what the rule of thirds was for anyway.
My point is is if you don't dive to thirds and be even more conservative all you are giving up is maybe 100-200 meters more penetration, but what you are gaining is a ton of safety margin.
The day that sh!t hits the fan I would prefer having way more gas in reserve than exactly enough.

[LCF]

You know, I've often wondered about the "catastrophic gas loss at max pen" idea. But over time, I've dived with some folks who have major problems with shutdowns, even after cave classes, so I can see how even a simple major leak could turn into a mess, if you can't get your valves shut quickly or without kicking up silt (which could make it hard for your buddy to get to you and get it done for you).

I had always been taught to do valve shutdown drills slowly and deliberately, but my Full Cave instructor made me do them FAST, and I was glad of it.

[NEON]

Although highly unlikely it is possible so why not have all your bases covered and plan for that? I thought that is what the rule of thirds was for anyway.
My point is is if you don't dive to thirds and be even more conservative all you are giving up is maybe 100-200 meters more penetration, but what you are gaining is a ton of safety margin.
The day that sh!t hits the fan I would prefer having way more gas in reserve than exactly enough.

+1.

[NEON]

I do not intend to derail the discussion but is clipping a stage to the crotch considered DIR?

[FW]

I do not intend to derail the discussion but is clipping a stage to the crotch considered DIR?
No.

[RN]

How does one of you have a complete gas loss diving sidemount

It's not likely, but not everyone here is diving sidemount.




I do for the most part total loss of backgas at max penetration is a boogeyman and just doesn't happen IMO

You keep thinking that. Most people don't win the lottery but they keep playing. Also, if I recall correctly, Sheck or one of his buddies experienced a total gas loss at maximum penetration and almost died. Forrest, I think you're the one who wrote about that incident here on the board.



I'm glad to see more discussion here supporting not diving to 1/3s. Forrest, you are correct, the poll is not about breaking 1/3s, it's about being more conservative. The first option means you turn before 1/3s, the second option means you always turn when you reach a turn pressure of 1/3s. The third option means you only breathe to 1/3s if there are at least 3 divers on your team.

Personally, I do not think diving 1/3s with only 2 team members is conservative enough. Even diving with 3 team members it might not be because teams can become separated. Like Mike, I often dive with a stage I don't touch or count in planning my turn pressure. I really don't understand the resistance on this. No one has ever died with too much gas, yet there are people here that are arguing that you shouldn't bring gas into a cave with you that you aren't going to use. That's silliness!!

[jj1987]

Also, if I recall correctly, Sheck or one of his buddies experienced a total gas loss at maximum penetration and almost died. Forrest, I think you're the one who wrote about that incident here on the board.
They were on air at a depth >150ft if memory serves me correctly. The issue was that the buddy thought it was Sheck's leak from how I heard the story. I guess if you're nice and buzzed, mistakes happen....but throwing extra gas at a intoxicated diver isn't the answer I would choose, seems like giving someone who's drunk a walking cane so they don't fall over...it might stop the end result, but it's not attacking the root of the problem.


But over time, I've dived with some folks who have major problems with shutdowns, even after cave classes, so I can see how even a simple major leak could turn into a mess, if you can't get your valves shut quickly or without kicking up silt (which could make it hard for your buddy to get to you and get it done for you).
I'm not sure that the nss-cds/nacd training standards require valve drills. I know for a fact I've seen NACD instructors teach who didn't even have an isolator.

[phillip1]

why is this even a discussion, i see that many people instead of adding safety and redundancy to a dive choose to actually reduce safety.
It seems ridiculous any way you look at it as you are only talking a very small distance/time further in, however in a real emergency situation that extra gas could make a big difference.

I understand that some people feel that in SM it is so very remote to have a OOA, but if I or my buddy were to loose all the gas of one tank (more likely but still remote) I would feel way better knowing that we were NOT diving to thirds and that we both have more than enough air to get out.

[LiteHedded]

I do not intend to derail the discussion but is clipping a stage to the crotch considered DIR?

It's fine.

[PfcAJ]

I always dive thirds or less, but not because I'm worried about losing all my gas (which has never happened with a sensible END and iso manifold), but because I want enough gas relative to my penetration distance to handle issues.

Total surprise loss of back gas just doesn't happen, and it certainly doesn't happen at max penetration.

[DA Aquamaster]

I haven't seen that many stages pointing straight up, or even at a 45. I think most people have enough sense to clip them.

Maybe on a leash...Show me a picture of a one or more empty stasges on a leash and I'll point out what I'm talking about. Just because you can't see what your empty stages are doing in the water, does not change what is happening.

I don't understand your leash reference at all. A leash creates real estate to handle more bottles, but "out of sight out of mind" just does not change how they float tail up when empty, especially when nose clipped to a leash, and it would take a real moron to nose clip anything other than a neutral or positive bottle, so the bottle is going to float tail high - I guess it doesn't count if you can't see it.


agreed. if you don't like how the empty stage rides clip if off to the crotch.It's potentially a good idea. How many
divers actually do it this way?


but to float that full stage you're going to have to add gas to the wing. that WILL create more dragI agree that extra gas has weight and that weight has to be accomodated with more gas in the wing.

The point you seem to be missing is that when you carry the same amount of gas in a wing and a stage, the remaining gas is going to weigh the same whether you breathe out of the back gas or the stage. If you breathe gas out of the stage, it starts to get positively bouyant. If you breathe that same amount of gas out of the back gas, the back gas tanks get less negatively buoyant by exactly the same amount.

The point is not whether a diver uses a safety bottle to carry part of the reserve versus breathing out of a stage and carrying all of the reserve in back gas. The point is that any time you carry a large reserve of gas, the weight penalty you pointed out will be present and how it is carried has zero impact on that total weight penalty.


I'm still confused as to why anyone would leave their safety gas in the front of the cave where it's least likely to be needed, but then again we don't seem to see eye to eye on risk analysis, as I wouldn't bring a pony bottle (:yawinkle:) for the grand traverseIts's not an issue of leaving your reserve near the front of the cave, it's about increasing your over all reserve.

As noted previously, if a diver wants to increase the reserve, which is partly what the thread is about, they can tsanke and use a stage or they can carry that stage as a safety bottle, which is where some of the controversy in the thread happens to be.

A two person team going from P1 to OG is a good example to look at. Although we have to start with the actual scenario - each diver took a stage but used it as a stage to just short of the peanut restriction to increase the back gas reserve while still leaving a portion of the reserve in back gas.

What was desired was an increased gas reserve as well as to allow more options in the event any gas loss occurred. From your risk assessment perspective, you may feel that was a wasted effort and would have chosen to just dive it on backgas. From our risk management perspective it made more sense to take more gas, to provide more options in the event something unexpected happened.

[DA Aquamaster]

I am not understanding the logic of a total failure being "very possible" in backmount - at least with an isolator manifold. I've never actually heard of one, so it's more of a theoretical multiple failure possiblity than a legitamate concern.

Although highly unlikely it is possible so why not have all your bases covered and plan for that? I thought that is what the rule of thirds was for anyway.
My point is is if you don't dive to thirds and be even more conservative all you are giving up is maybe 100-200 meters more penetration, but what you are gaining is a ton of safety margin.
The day that sh!t hits the fan I would prefer having way more gas in reserve than exactly enough.Read the rest of my post you quoted and you'll see I am supoporting your position, just not from the the perspective of needing to cover a long shot total gas loss scenario. I'm one of the guys on the "take a big reserve" side of the argument.

[phillip1]

I always dive thirds or less, but not because I'm worried about losing all my gas (which has never happened with a sensible END and iso manifold), but because I want enough gas relative to my penetration distance to handle issues.

Total surprise loss of back gas just doesn't happen, and it certainly doesn't happen at max penetration.

Well total gas loss although unlikely could happen anywhere, what does max penetration have that is different than other parts of the cave were gas loss could occur other than being the worse place it could happen?

[DA Aquamaster]

Well total gas loss although unlikely could happen anywhere, what does max penetration have that is different than other parts of the cave were gas loss could occur other than being the worse place it could happen?There is some validity in what you are saying as well as with AJ's point of view and it might work best to look at them both together.

Statistically, a total gas loss with no prior warning is an extremely remote possibility. A ruptured burst disc is arguably the quickest way to lose gas, and that occurs at about 1 cu ft per second. Assuming you have double cave filled 95s or HP 130s (both hold about the same 260 cu ft), you are diving "thirds" and rupture the burst disc at the turn point:

At the time of the failure, you'll have about 173 cu ft. If it takes you a full minute to close the isolator, you'll still have about 110 cuft of gas for exit compared to the 87 you used getting there. Even if you take 2 minutes to isolate, you'll still have in the ballpark range of 50 cu ft. That means you'd need only 40 cu ft or so of gas from your teammate(s) 87 cu ft reserve to safetly exit, assuming you can exit on the same gas you entered with.

So you can screw up badly and still have some gas left that leaves you with more than a reserve "third" to exit. That means you either have to really screw up running the valves, or you have to have a second failure on the remaining post.

You are entirely correct that there is an equal chance of a total failure anywhere in the dive, but AJ is correct that you have to be really unlucky to have an extremely unlikely total gas failure and have it at the point of max penetration.

If the odds are 1 in 1,000 (most of us would agree the odds are far longer, but 1 in 1000 works for general speculation) of having a total gas loss on a 120 minute dive, the odds of having it happen 3 minutes either side of the turn point are then 1 in 20. So in effect, the odds of the worst case scenario are going to be in the 1 in 20,000 range. Not something you need to lose sleep over.

That said, other stuff can happen, especially if you are not on top of things. All that escaping gas can create some impressve percolation effects, in the course of shutting off the post you could get sloppy, break trim and create a silt out, if you are having an off day and are short on SA, you might not get on the line before the viz goes to zero and you may have to search for it before starting the exit, etc, etc. In short, the single failure can still precipitate a chain of events that further delay the exit, making an ample reserve in excess of thirds a good idea in some situations.

[phillip1]

I understand your point however I do not agree and prefer to be prepared for the super remote possibility of a total gas loss and not dive to thirds.
The more likely scenario would be some other kind of problem and having extra gas to deal with it could be a life saver.

This is kind of like the safety reel, how many of you actually lost the line to the point that you actually did need to do a line search?
I have never had to use my safety reel ever (touch wood) yet I always carry two (finger spools) at all times just in case I do need to do a lost line search in zero viz and I accidentally drop one.
I know some people are going to think that I am ridiculous to carry two, but it is a likely scenario and if you do drop a safety reel and can't find it in a real lost line zero viz siltout you are in really big trouble, so I always carry two.

I like having all my bases covered as best possible.

[RN]

They were on air at a depth >150ft if memory serves me correctly. The issue was that the buddy thought it was Sheck's leak from how I heard the story. I guess if you're nice and buzzed, mistakes happen....but throwing extra gas at a intoxicated diver isn't the answer I would choose, seems like giving someone who's drunk a walking cane so they don't fall over...it might stop the end result, but it's not attacking the root of the problem.

Different incident.

[jj1987]

Different incident.
I would be interested in hearing more information if you (or FW) have it.

[limeyx]

I do not intend to derail the discussion but is clipping a stage to the crotch considered DIR?

The tail, yes (it keeps the stage closer in to the body and helps to avoid damaging the cave)
Assuming by "Crotch" you mean scooter D-ring or something in that vicinity.
GUE is quite practical when it comes to methods to keep stages off the cave walls/ceiling/floor

[SuPrBuGmAn]

Show me a picture of a one or more empty stasges on a leash and I'll point out what I'm talking about. Just because you can't see what your empty stages are doing in the water, does not change what is happening.

I don't understand your leash reference at all. A leash creates real estate to handle more bottles, but "out of sight out of mind" just does not change how they float tail up when empty, especially when nose clipped to a leash, and it would take a real moron to nose clip anything other than a neutral or positive bottle, so the bottle is going to float tail high - I guess it doesn't count if you can't see it.

My leash reference was saying that they end up floating vertical, like you are saying.

My post was saying that most divers staging a bottle(not talking about leashes) don't have near vertical bottles(or 45* angles). I think its pretty rare to see that nowadays.



I'm not saying I don't ever see it happening, but its hardly a regular sight.

I do like all the "out of sight out of mind" refferences though, aimed at anyone in particular? :P

[RN]

I would be interested in hearing more information if you (or FW) have it.

When I get a chance I'll look for the post on it. All I remember right is they had done a pretty significant penetration (for their time) with multiple stages and had a complete gas loss at max penetration. They barely got back to their stages as they were running out of gas in the bottles they had on them.

[LiteHedded]

When I get a chance I'll look for the post on it. All I remember right is they had done a pretty significant penetration (for their time) with multiple stages and had a complete gas loss at max penetration. They barely got back to their stages as they were running out of gas in the bottles they had on them.

i think that story is in caverns measureless. and the END was questionable and they made mistakes in diagnosing the problem. I could be wrong. maybe it's a different incident.

I guess my point with this whole thing is why stop there? what if your buddy's right post fails after he donates to you? where does it all end?
you have to pick your poison with what types of (and how many) failures you're going to plan for. You can very quickly plan yourself right out of a dive when you start planning for unreasonable failures.

[DA Aquamaster]

i think that story is in caverns measureless. and the END was questionable and they made mistakes in diagnosing the problem. I could be wrong. maybe it's a different incident.

I guess my point with this whole thing is why stop there? what if your buddy's right post fails after he donates to you? where does it all end?
you have to pick your poison with what types of (and how many) failures you're going to plan for. You can very quickly plan yourself right out of a dive when you start planning for unreasonable failures.Absolutely. Planning for multiple failures quickly makes the logistics untenable or leads to the conclusion that going in caves at all is not worth the risk.

Rebreather diving and bailout requirements have complicated the picture somewhat, but in the past, the concept was to plan and configure so that each diver had full redundancy and was capable of self rescue/exit after any single failure, combined with a team approach to increase the support, resources and reserves available, which has a side effect of providing some cushion against multiple failures. Of course it can be argued that this then has an unintended side effect of increasing the overall potential for anyone on the team to have a single failure.

For example: a diver on a three person team loses all their gas and shares with diver number two who then has a reg failure, requiring the OOA diver to move to diver number 3. There are all kinds of statistical possibilities here.

1. If diver 1 were never on the team, the total gas loss would not have occured and,
2. The reg failure on diver number 2 may not have occurred, or never been noticed.
3. If diver two were not along, the reg failure would not have occurred and diver 1 would have just borrowed gas for the exit form diver "3".
4. If diver 3 had not been along, both failures would have occurred and the dive would have gotten very interesting.

But it is important not to lose sight of the very low probabilities of each failure, let alone the exponentially lower probability of two very low probaility failures occurring on one dive. This is especially true when many of the configuration decisions and pre-dive procedures are intended to keep the probabilities of failures very low.

[NEON]

Since when has plannig for a total gas loss at maximum penetration become unreasonable? :roll:

[Slüdge]

Since when has plannig for a total gas loss at maximum penetration become unreasonable? :roll:

I don't know to which post you were referring, but if it's DA's, he's talking a double catastrophe. Do we plan for that? No, we don't. Think about two divers with doubles. One guy has a total gas loss, and a minute later the other does. They're dead.

I was thinking about this as I was pushing a dead scooter out from p1,900' at Jackson Blue yesterday. My dive plan is breathe a stage and let my doubles be reserve. What if, after my scooter died, I were to lose my backgas? Pushing a scooter out instead of riding it will deplete my stage bottle, causing me to have to go to backgas, and if it isn't there, I'm dead.

So what's the answer?

[LiteHedded]

I don't know to which post you were referring, but if it's DA's, he's talking a double catastrophe. Do we plan for that? No, we don't. Think about two divers with doubles. One guy has a total gas loss, and a minute later the other does. They're dead.

I was thinking about this as I was pushing a dead scooter out from p1,900' at Jackson Blue yesterday. My dive plan is breathe a stage and let my doubles be reserve. What if, after my scooter died, I were to lose my backgas? Pushing a scooter out instead of riding it will deplete my stage bottle, causing me to have to go to backgas, and if it isn't there, I'm dead.

So what's the answer?

another example where you have to pick your poison. if you have scooter failures that cause you to have to swim out AND you lose all your backgas, it's just not your day.

assuming no tow scooter (which makes things dicey from the get-go) i would reserve either enough gas to swim out OR share gas with a buddy while towing. to expect both to happen is just as unlikely as cave goblins stealing your gas right when you thumb a dive.


just curious btw, what happened to ur scooter russell?

[Slüdge]

The clutch broke - it just snapped in half.

The funny thing was, I won an aluminum clutch from Rodney's guessing game but he didn't ship it to me yet. Edd gave me a new one and told me when the one comes in the mail from Rodney, to just give that one to him. Is Cave Adventurers awesome or what?

BTW, I went into "total relaxation mode" and exited the cave with 1,200psi in my stage, and didn't have to use backgas after all. But you still think about things like that.

[phillip1]

Since when has plannig for a total gas loss at maximum penetration become unreasonable? :roll:

I could not agree more, especially since planing as safely as possible for that entails very little more if even anything more than diving to thirds or less (to be even more conservative).

When we did a really long 2.5 hour penetration a while ago with Thomas, at max penetration after making the final tie off, we paused for like 30 secs or so to enjoy the moment before turning back, we had a 2.5 hour swim out more or less.
Now should the extremely unlikely remote major gas loss happen or anything else at that or any other point in our dive we would have a greater margin of safety as we both had more than thirds in back gas and also more than thirds in our stages.

What did this cost us, about 200 mtrs less penetration maybe.
To each his own I just find it gives you a greater safety margin in case one of those Oh Sh!t moments should ever happen.

[PfcAJ]

I think "thirds" is a great strategy, and should certainly be adhered to (or more conservative). However, total loss of my gas isn't my reason for diving it. I can reach all my valves, practice it regularly, and I can do so without losing control of my buoyancy or position in the water.

[jj1987]

I could not agree more, especially since planing as safely as possible for that entails very little more if even anything more than diving to thirds or less (to be even more conservative).

When we did a really long 2.5 hour penetration a while ago with Thomas, at max penetration after making the final tie off, we paused for like 30 secs or so to enjoy the moment before turning back, we had a 2.5 hour swim out more or less.
Now should the extremely unlikely remote major gas loss happen or anything else at that or any other point in our dive we would have a greater margin of safety as we both had more than thirds in back gas and also more than thirds in our stages.

What did this cost us, about 200 mtrs less penetration maybe.
To each his own I just find it gives you a greater safety margin in case one of those Oh Sh!t moments should ever happen.
You're swimming in a no-flow cave, correct? Completely different than what a lot of us dive, and why we're saying that gas math can fluctuate from dive to dive.

The fact is we all interpret risks differently. For instance, you've mentioned before that you solo dive, and IMO this is much riskier than diving 1/3rds even in a no flow system. You're doing swims in the range of 5 hours total, and with modern scooter technology, I feel this is an unnecessary risk due to diver fatigue or cramping which could severely delay exit, or over exerting and possibly dehydrating yourself and increasing DCS risk at what I believe is a remote location.

I know one poster in this topic who is seeming very conservative with gas planning (certainly carries more gas than I do), has mentioned on other boards he solo's and dives ENDs up to 150ft sometimes.

I'm not saying either of us are right, that's not something that we're going to conclude on an online forum. I'm simply saying that every one on here interprets and manages risk differently.

This thread focuses on ONE way to manage risk. I personally don't believe the recent cave deaths that I've read about would be prevented with a few 100 psi of extra gas.

[Spd 135]

You're swimming in a no-flow cave, correct? Completely different than what a lot of us dive, and why we're saying that gas math can fluctuate from dive to dive.

The fact is we all interpret risks differently. For instance, you've mentioned before that you solo dive, and IMO this is much riskier than diving 1/3rds even in a no flow system. You're doing swims in the range of 5 hours total, and with modern scooter technology, I feel this is an unnecessary risk due to diver fatigue or cramping which could severely delay exit, or over exerting and possibly dehydrating yourself and increasing DCS risk at what I believe is a remote location.

I know one poster in this topic who is seeming very conservative with gas planning (certainly carries more gas than I do), has mentioned on other boards he solo's and dives ENDs up to 150ft sometimes.

I'm not saying either of us are right, that's not something that we're going to conclude on an online forum. I'm simply saying that every one on here interprets and manages risk differently.

This thread focuses on ONE way to manage risk.

Phillip1 may be diving caves that you cannot scooter and are sidemount or no mount caves. I was in a river cave, this weekend, that I scootered once, but won't again til I get a better light as it is a very dark cave so I had to scooter very slow due to its constant up and down and turning tunnel. The flow in this cave is awful. The river is proabably 10 feet above normal and the flow is not affected a bit. Sometime swimming is your only option and then gas management is extremely critical as the swim out (if no flow) may take longer than the swim in due to fatigue.

[phillip1]

Very good point everyone interprets risk differently, I personally feel safer with never diving to thirds, I also agree that the extra reserve will almost certainly be used (god forbid) for another type of emergency.
As for the long swims I agree on the increased risks but we don't have any scooters at the moment (working on that though), however increasing safety by reserving more gas in case of an emergency is the way to go I feel.
Those types of dives are super tiring but I also keep in shape and surf almost every day for 3-4 hours so a long swim like that I can handle.
It would be kind of dicey doing those long dives not being in shape though.

I always drink the cave water here when it's in a remote location I think it's safe however never in the caves near or under cities like Cueva Taina or El Tildo.
I have never been sick from cave water here so far, I did feel like I was going to die of extreme food poisoning once from the food on an Air France flight.

[jj1987]

Phillip1 may be diving caves that you cannot scooter and are sidemount or no mount caves. I was in a river cave, this weekend, that I scootered once, but won't again til I get a better light as it is a very dark cave so I had to scooter very slow due to its constant up and down and turning tunnel. The flow in this cave is awful. The river is proabably 10 feet above normal and the flow is not affected a bit. Sometime swimming is your only option and then gas management is extremely critical as the swim out (if no flow) may take longer than the swim in due to fatigue.
I think he's posted looking for a scooter, so I don't think this applies. It was more of a hypothetical example of how different people see risk anyways...


I always drink the cave water here when it's in a remote location I think it's safe however never in the caves near or under cities like Cueva Taina or El Tildo.
I have never been sick from cave water here so far, I did feel like I was going to die of extreme food poisoning once from the food on an Air France flight.
FWIW (and off topic) I use a camelback during longer dives. It fits nicely on a stage botlte, or on backgas. I don't like the idea of drinking even spring water that I haven't had tested, I see the risk as minimal, but it exists. Also I think a lot of these recent semi-serious dcs hits are due to dehydration, and there's simply no excuse to get bent for that reason when tap water is free and a camelback costs $35.

Here's a pic...I was trying it on backgas, but I think it works better attached the same way on a stage bottle, if it ever got hung it would be easier to untangle-
http://hphotos-snc3.fbcdn.net/hs065.snc3/13297_586477164915_201400707_34458737_5039055_n.jp g

[SuPrBuGmAn]

Capri Sun pouches are also hella easy to drink submerged if you guys are getting thirsty.

[LiteHedded]

Capri Sun pouches are also hella easy to drink submerged if you guys are getting thirsty.

ya but then you have to manage the trash
I like camelbaks as well. i only bring them in nastier systems tho

[SuPrBuGmAn]

Stick the straw into the pouch, stick the entire pouch into your wetnotes/pocket/wetsuit sleave(Oh my) :)

[Ben M]

ya but then you have to manage the trash
I like camelbaks as well. i only bring them in nastier systems tho

I found a candy bar wrapper in a side passage in Jackson Blue one dive. This was diver placed as its location was such that it was not possible to have entered into the system any other way. :smt102

[phillip1]

I think he's posted looking for a scooter, so I don't think this applies. It was more of a hypothetical example of how different people see risk anyways...


FWIW (and off topic) I use a camelback during longer dives. It fits nicely on a stage botlte, or on backgas. I don't like the idea of drinking even spring water that I haven't had tested, I see the risk as minimal, but it exists. Also I think a lot of these recent semi-serious dcs hits are due to dehydration, and there's simply no excuse to get bent for that reason when tap water is free and a camelback costs $35.

Here's a pic...I was trying it on backgas, but I think it works better attached the same way on a stage bottle, if it ever got hung it would be easier to untangle-
http://hphotos-snc3.fbcdn.net/hs065.snc3/13297_586477164915_201400707_34458737_5039055_n.jp g

We do that too now (albeit a bit different in SM) since we dive the Razor, we use the MSR dromedary (BAT wing) and put about a liter of water in it and it also serves as the buoyancy device you can drink from it during the dive, works really well.
We sometimes used to bring water in plastic bags that they sell here (choice between plastic bottles or bags).
That worked very well but kind of took up room in the pockets when full.

for me if I am on a long dive and thirsty I will drink cave water (in the DR that is) if I don't have anything else.

As for drinking cave water I think far back in the cave if it's in the jungle not near any houses or anything it's ok, at the entrance it would be much more unsafe.

I have a question, I always drink a lot like a liter or more of water in the 20-30 mins prior to a long dive, if I were to not drink again for like 4-5 hours (would not do it anyway but curious) would I get dehydrated?

[LiteHedded]

We do that too now (albeit a bit different in SM) since we dive the Razor, we use the MSR dromedary (BAT wing) and put about a liter of water in it and it also serves as the buoyancy device you can drink from it during the dive, works really well.
We sometimes used to bring water in plastic bags that they sell here (choice between plastic bottles or bags).
That worked very well but kind of took up room in the pockets when full.

for me if I am on a long dive and thirsty I will drink cave water (in the DR that is) if I don't have anything else.

As for drinking cave water I think far back in the cave if it's in the jungle not near any houses or anything it's ok, at the entrance it would be much more unsafe.

I have a question, I always drink a lot like a liter or more of water in the 20-30 mins prior to a long dive, if I were to not drink again for like 4-5 hours (would not do it anyway but curious) would I get dehydrated?

todd leonard has made some interesting posts about in-dive hydration on thedecostop. he's done some amazing long range exploration dives and his posts are worth a read on the subject. I think his username is toddl if you wanted to search for them over there.

[DA Aquamaster]

I know one poster in this topic who is seeming very conservative with gas planning (certainly carries more gas than I do), has mentioned on other boards he solo's and dives ENDs up to 150ft sometimes.

I'm not saying either of us are right, that's not something that we're going to conclude on an online forum. I'm simply saying that every one on here interprets and manages risk differently.

This thread focuses on ONE way to manage risk. I personally don't believe the recent cave deaths that I've read about would be prevented with a few 100 psi of extra gas.I think what you are speaking to is the need to look at the whole picture and not just focus on one magic bullet to solve all the safety/conservatism issues.

There are a variety of factors that may prompt someone to increase the gas reserve: deeper ENDs, diving solo, diving in unfamilar systems, etc, could all be reasons to rachet the gas planning conservatism up a notch.

[RN]

I guess my point with this whole thing is why stop there? what if your buddy's right post fails after he donates to you? where does it all end?
you have to pick your poison with what types of (and how many) failures you're going to plan for. You can very quickly plan yourself right out of a dive when you start planning for unreasonable failures.

I stop there because that's where I feel comfortable. When you start to bring multiple failures into the equation, then you might as well stop cave diving. We all plan for gas loss due to failure. Why does anyone think it might NOT happen at maximum penetration?? It's going to happen when it happens. Hopefully, it never happens. I just don't understand why so many of you are against being a little more conservative than 1/3s!



You're swimming in a no-flow cave, correct? Completely different than what a lot of us dive, and why we're saying that gas math can fluctuate from dive to dive.

The fact is we all interpret risks differently. For instance, you've mentioned before that you solo dive, and IMO this is much riskier than diving 1/3rds even in a no flow system. You're doing swims in the range of 5 hours total, and with modern scooter technology, I feel this is an unnecessary risk due to diver fatigue or cramping which could severely delay exit, or over exerting and possibly dehydrating yourself and increasing DCS risk at what I believe is a remote location.

Not all of us dive Devil's every week. In fact, I'd say many of us dive in conditions similar to what Philip is diving. As for solo diving, some dives are safer solo than they are with a buddy. I also don't typically scooter passage I haven't swam before. Many of the dives I've been doing lately in JB involve scootering 20-30 minutes back, doing a 1.5-2.5 hour swim dive, and scooter back. Get out of the box of Devil's.

[jj1987]

Phillip1 may be diving caves that you cannot scooter and are sidemount or no mount caves. I was in a river cave, this weekend, that I scootered once, but won't again til I get a better light as it is a very dark cave so I had to scooter very slow due to its constant up and down and turning tunnel. The flow in this cave is awful. The river is proabably 10 feet above normal and the flow is not affected a bit. Sometime swimming is your only option and then gas management is extremely critical as the swim out (if no flow) may take longer than the swim in due to fatigue.
Completely understand that one...and god forbid you try to canoe there if it's where I think you're referring to (isn't it a few miles from a boat ramp?)...you might just give up and drown :-P


As for solo diving, some dives are safer solo than they are with a buddy.
I felt the same way about Royal. I haven't been back since because the risk there is beyond what is acceptable for me personally. Just as you choose to get more conservative on gas, I choose to sit out the dive, and we're back to my point about risk assessment. Don't get me wrong, I think dives like Marius connecting the Fl room and harper tunnel, the new ginnie, what you and Ed have done at JB, etc is amazing, and interesting to me, but it's outside of my comfort zone. The risk/reward that I perceive just doesn't equal out FOR ME...but keep posting dive reports and stories, I do find them interesting.


I just don't understand why so many of you are against being a little more conservative than 1/3s!
Truthfully Rob, I've yet to see a cave death that could have been prevented by 200psi more gas. That's really what it all boils down to for me...

2009 Devils - Multiple visual jumps and didn't even know what tunnel they were in, buddy went to the opposite side of the cave to search.
2009 Devils - Medical condition with plenty of gas
2008 Waynes World - Had a full tank and didn't realize isolator was closed.
2008 Devils - theoretically had enough gas to get home but fiddled with a breather
2008(9?)- JB Medical condition with plenty of gas
2008(9?)- JB Breather issue of some sort
2005 - Peacock 3 - single tank and I'm going to guess the castle on air?
2004 - Eagles Nest again, high END
2003 - Little River over 1000ft back at time of death
2003- Cow over 1000ft back with 2000psi of gas
2002 - Peacock medical condition
2002 - Ginnie wrong gas
2001- JB Wrong gas (13% o2 according to iucrr)
2001- Royal springs over 500ft back at time of death (if they were backmount, I don't think they could have gotten that far, but IUCRR report says that... I didn't get much past p300 in there), likely died going the wrong way, more gas would have put them further if possible.
2000- Little River 900ft from exit.

There's trends I'm putting together, but I don't care enough to hash it out on a public forum, there's so many variables in every accident that we're each going to draw our own conclusions. I'm sure there's details I missed on some of these IUCRR reports, but my own hypothesis is that even an extra 100cu ft of gas wouldn't have changed many of the deaths I've found detailed record of.

Really what this comes to for me at least, is that thinking 100, 200, or 300psi is going to safe a life is not a theory I buy into. I think surveying on exit, diving unfamiliar cave, diving when you know you're getting physically tired, diving a cave where you know peculation or silt will delay exit, siphons, etc are all GREAT reasons to back off 1/3rds, but sudden and complete loss of gas isn't necessarily the first reason to do it. I think that's what PFCAJ, Litehedded, and myself were trying to say, but maybe didn't get across. I don't think either of the 3 of us have put any time into thoughts on how to manage solo gas or gear, so maybe we were having the same conversation with different context in mind? Either way, thanks for the discussion, it's brought up some interesting points.

[SuPrBuGmAn]

Completely understand that one...and god forbid you try to canoe there if it's where I think you're referring to (isn't it a few miles from a boat ramp?)...you might just give up and drown :-P


He's got one of the more ideal cave diving boats that I've been on, no worries with paddling :)

[LiteHedded]

I stop there because that's where I feel comfortable. When you start to bring multiple failures into the equation, then you might as well stop cave diving. We all plan for gas loss due to failure. Why does anyone think it might NOT happen at maximum penetration?? It's going to happen when it happens. Hopefully, it never happens. I just don't understand why so many of you are against being a little more conservative than 1/3s!




Not all of us dive Devil's every week. In fact, I'd say many of us dive in conditions similar to what Philip is diving. As for solo diving, some dives are safer solo than they are with a buddy. I also don't typically scooter passage I haven't swam before. Many of the dives I've been doing lately in JB involve scootering 20-30 minutes back, doing a 1.5-2.5 hour swim dive, and scooter back. Get out of the box of Devil's.
I never said that

[DA Aquamaster]

I think surveying on exit, diving unfamiliar cave, diving when you know you're getting physically tired, diving a cave where you know peculation or silt will delay exit, siphons, etc are all GREAT reasons to back off 1/3rds, but sudden and complete loss of gas isn't necessarily the first reason to do it.Well stated. That's exactly the point. It is not as much a thirds/not thirds discussion as it is a discussion that there are far better reasons with far higher probabilities to justify being more conservative on gas planning in some situations.

[LiteHedded]

Well stated. That's exactly the point. It is not as much a thirds/not thirds discussion as it is a discussion that there are far better reasons with far higher probabilities to justify being more conservative on gas planning in some situations.

yes.
as you progress in cave diving, planning gets a tad more involved than rules of thumb like thirds allows for. being afraid of this 'disappearing gas' boogey man is not the way to create thinking divers.

we often dive more conservatively than thirds, so that's not what I'm saying.

[Caver95]

'disappearing gas' boogey man.

HOLLY **** and this whole time I have been worried about the Florida Skunk Ape.

[LiteHedded]

HOLLY **** and this whole time I have been worried about the Florida Skunk Ape.

lol
don't stop worrying about the skunk ape. that's just what he wants.

[Caver95]

lol
don't stop worrying about the skunk ape. that's just what he wants.

he lolls you into a false sense of security with these internet forums, and then WHAM! your wifes knocked up with a little hairy beast.

[jj1987]

he lolls you into a false sense of security with these internet forums, and then WHAM! your wifes knocked up with a little hairy beast.

You owe me a new keyboard.

[LiteHedded]

he lolls you into a false sense of security with these internet forums, and then WHAM! your wifes knocked up with a little hairy beast.

yes. it's the skunk ape that keeps doing that. the skunk ape...

[phillip1]

As many have stated total loss of gas is not the main reason to reserve more than thirds, I totally agree, it is far more likely that some other problem will happen to delay the exit, so then my question is why not reserve more than thirds since many other potentially major problems are much more likely?

I dive mainly in unknown systems with all the associated hazards, but I still am as conservative no matter were I dive, I do not have 2 levels of conservatism I think that's a big mistake, I approach every cave with the same amount of caution and conservatism, whether it's a first exploration dive in an unknown gnarly cave or a dive in a known, lined and mapped cave system.

I think in some ways a well dove cave with many t's and jumps etc.. could turn out to be far more confusing and dangerous than a cave I just layed line in, there have been many accidents were cave divers got lost or disorientated and died in caves that did not have any percolation etc..
This was by divers making a mistake, not paying attention, visual jumps etc.., but we could ALL make a mistake, no one is above that, and really need that extra gas reserve.

It is by no means a silver bullet but it can never hurt and could only help if need be.

[jj1987]

so then my question is why not reserve more than thirds since many other potentially major problems are much more likely?
How much are you backing off 1/3rds? What makes you choose that specific number? Let's throw some real numbers out there so we can have the discussion, otherwise for all I know the person swearing they dont dive 1/3rds is diving 200psi less than 1/3rds!

[phillip1]

thirds + 20 bar in each tank I choose that number because it would give me about 10-15 mins extra time above thirds more or less (I don't dive deep systems) in case I need it.
I also do +20 on all my stages and I have a nice extra reserve in each tank.

This has in no way hindered my penetrations to any significant level at all.

[OFG-1]

Let's throw some real numbers out there so we can have the discussion, !

So, if you only want real numbers, we cant discuss X^2 = -1?
OK then, how about 6.23 X 10^23? That's a real number.

[Mike Edmonston]

How much are you backing off 1/3rds? What makes you choose that specific number? Let's throw some real numbers out there so we can have the discussion, otherwise for all I know the person swearing they dont dive 1/3rds is diving 200psi less than 1/3rds!

James, the numbers really don't matter. It's a comfort issue. People will push it to their comfort level in Gas use, depth, penetration etc... It's the same as asking everyone what their favorite color is.

I have already stated my preference. I carry extra gas. My wife is my cave buddy, and I would like to keep her around as long as possible, so I carry an extra tank. Sometimes, if it's a deeper or unfamiliar system, we BOTH carry bailouts but still dive to thirds.

For example, If you ever saw us dive little river together, you'll see us both slinging 80's. Usually we take a nice leisurely dive to the Florida room, or make the serpentine circuit etc... but we still carry the reserve.

It's one less thing I have to worry about.

I'll give you another example. When I dive an unfamiliar system, or a new passage (to me) in a FAMILIAR system, I will drop my own cookie / arrow / clothepin etc... on the guideline every 400' or so. Do I need to? Nope! But it makes me feel warm and fuzzy when I see it on the way back out.

So the answer to your question is to dive to your comfort level, and follow whatever procedure (1/3 - bailout - stages etc...) makes YOU feel save.

Safe diving to you :-)

Cheers

[phillip1]

yeah.

[Spd 135]

So, if you only want real numbers, we cant discuss X^2 = -1?
OK then, how about 6.23 X 10^23? That's a real number.

There is no need for that kind of language here...................Anybody? What did he say? ;) Y'all are way too smart for me.

[MORGAN]

So, if you only want real numbers, we cant discuss X^2 = -1?
OK then, how about 6.23 X 10^23? That's a real number.

Was Avogadro a cave diver?

Mike

[OFG-1]

Was Avagadro a cave diver?

Mike

He must have been, he described moles, and moles dig little caves. I have them all over the place with their pointy little snoots.

[MORGAN]

He must have been, he described moles, and moles dig little caves. I have them all over the place with their pointy little snoots.

I believe you have something there! And a mole is pretty small - at least the dead ones the cat leaves on the steps are. They are hardly worth dressing out and cooking. If a mole is made up of 6.023 x 10^23 molecules (little tiny moles, the mole equivalent of homunculi?), then a molecule must be pretty damn small! 1 / 6.023 x 10^23 of anything wouldn't be very much.

Maybe if moles were bigger they'd make bigger caves, and I wouldn't have to drive so far to go cave diving.

Mike

[RN]

Completely understand that one...and god forbid you try to canoe there if it's where I think you're referring to (isn't it a few miles from a boat ramp?)...you might just give up and drown :-P


I felt the same way about Royal. I haven't been back since because the risk there is beyond what is acceptable for me personally. Just as you choose to get more conservative on gas, I choose to sit out the dive, and we're back to my point about risk assessment. Don't get me wrong, I think dives like Marius connecting the Fl room and harper tunnel, the new ginnie, what you and Ed have done at JB, etc is amazing, and interesting to me, but it's outside of my comfort zone. The risk/reward that I perceive just doesn't equal out FOR ME...but keep posting dive reports and stories, I do find them interesting.


Truthfully Rob, I've yet to see a cave death that could have been prevented by 200psi more gas. That's really what it all boils down to for me...

2009 Devils - Multiple visual jumps and didn't even know what tunnel they were in, buddy went to the opposite side of the cave to search.
2009 Devils - Medical condition with plenty of gas
2008 Waynes World - Had a full tank and didn't realize isolator was closed.
2008 Devils - theoretically had enough gas to get home but fiddled with a breather
2008(9?)- JB Medical condition with plenty of gas
2008(9?)- JB Breather issue of some sort
2005 - Peacock 3 - single tank and I'm going to guess the castle on air?
2004 - Eagles Nest again, high END
2003 - Little River over 1000ft back at time of death
2003- Cow over 1000ft back with 2000psi of gas
2002 - Peacock medical condition
2002 - Ginnie wrong gas
2001- JB Wrong gas (13% o2 according to iucrr)
2001- Royal springs over 500ft back at time of death (if they were backmount, I don't think they could have gotten that far, but IUCRR report says that... I didn't get much past p300 in there), likely died going the wrong way, more gas would have put them further if possible.
2000- Little River 900ft from exit.

There's trends I'm putting together, but I don't care enough to hash it out on a public forum, there's so many variables in every accident that we're each going to draw our own conclusions. I'm sure there's details I missed on some of these IUCRR reports, but my own hypothesis is that even an extra 100cu ft of gas wouldn't have changed many of the deaths I've found detailed record of.

Really what this comes to for me at least, is that thinking 100, 200, or 300psi is going to safe a life is not a theory I buy into. I think surveying on exit, diving unfamiliar cave, diving when you know you're getting physically tired, diving a cave where you know peculation or silt will delay exit, siphons, etc are all GREAT reasons to back off 1/3rds, but sudden and complete loss of gas isn't necessarily the first reason to do it. I think that's what PFCAJ, Litehedded, and myself were trying to say, but maybe didn't get across. I don't think either of the 3 of us have put any time into thoughts on how to manage solo gas or gear, so maybe we were having the same conversation with different context in mind? Either way, thanks for the discussion, it's brought up some interesting points.

Not every cave diving incident gets published on the IUCRR site.

As for being conservative, you do bring up a good point. I do a lot of site seeing on the way out as well as the way in. I'm not one of those that thinks hitting turn pressure means it's time to head straight out of the cave. I actually prefer to learn the cave on the exit because when the sh!t hits the fan, that's how I want to know it. I've said this before and I'll say it again, there are certain systems in which if the line suddenly disappeared, as long as I have light, I can still get out. While I don't do much survey on the way out (usually on the way in), I will do minor exploration on the way out. I also dive unfamiliar cave on a pretty regular basis. So I have my reasons for being more conservative. But I think it's a good idea no matter what you're doing on your dive or where you're diving. Also, like Mike, my wife is my regular dive buddy and I want it to stay that way for a long time.

[jj1987]

Not every cave diving incident gets published on the IUCRR site.
The fact that I put a few in there that aren't on IUCRR would imply that I'm well aware of that. :yawinkle:

Unfortunately the reports which do not go public (and it seems like about half of them these days) are left to park bench speculation on things we heard from a friend of a friend of a friend who knows someone that was in the same town during the recovery...and there's not a whole lot of accurate conclusions we can draw from that. Confusing, too, because a dive buddy was on scene for one of the recent recovery efforts and a report was prepared :?

[LiteHedded]

Not every cave diving incident gets published on the IUCRR site.

As for being conservative, you do bring up a good point. I do a lot of site seeing on the way out as well as the way in. I'm not one of those that thinks hitting turn pressure means it's time to head straight out of the cave. I actually prefer to learn the cave on the exit because when the sh!t hits the fan, that's how I want to know it. I've said this before and I'll say it again, there are certain systems in which if the line suddenly disappeared, as long as I have light, I can still get out. While I don't do much survey on the way out (usually on the way in), I will do minor exploration on the way out. I also dive unfamiliar cave on a pretty regular basis. So I have my reasons for being more conservative. But I think it's a good idea no matter what you're doing on your dive or where you're diving. Also, like Mike, my wife is my regular dive buddy and I want it to stay that way for a long time.

that's for sure :roll:

[phillip1]

we could argue all day about this, the fact is more air will always help no matter how little more you have.
I think there have been a few deaths in Mex were cave divers drowned 5 mins from an entrance, one accident in Mayan Blue and one in Calimba (I may be wrong on locations). But I recall reading about the accident in Calimba two people drowned very close to the entrance and two made it out and ran out just before the entrance, I think these were divers with a few hundred cave dives under they're belts.

I think in this and any emergency scenario 200-300psi could make a big difference,
more air will always help no matter what the amount, and I think no one is above being in an accident and no matter how much experience one might have anyone could also make a mistake like, getting lost, tangled etc...
I think reserving more air is the way to go.

[RN]

we could argue all day about this, the fact is more air will always help no matter how little more you have.
I think there have been a few deaths in Mex were cave divers drowned 5 mins from an entrance, one accident in Mayan Blue and one in Calimba (I may be wrong on locations). But I recall reading about the accident in Calimba two people drowned very close to the entrance and two made it out and ran out just before the entrance, I think these were divers with a few hundred cave dives under they're belts.

I think in this and any emergency scenario 200-300psi could make a big difference,
more air will always help no matter what the amount, and I think no one is above being in an accident and no matter how much experience one might have anyone could also make a mistake like, getting lost, tangled etc...
I think reserving more air is the way to go.

:smt038 :smt038 :smt038 :smt038 :smt038

[argyris]

we could argue all day about this, the fact is more air will always help no matter how little more you have.
I think there have been a few deaths in Mex were cave divers drowned 5 mins from an entrance, one accident in Mayan Blue and one in Calimba (I may be wrong on locations). But I recall reading about the accident in Calimba two people drowned very close to the entrance and two made it out and ran out just before the entrance, I think these were divers with a few hundred cave dives under they're belts.

I think in this and any emergency scenario 200-300psi could make a big difference,
more air will always help no matter what the amount, and I think no one is above being in an accident and no matter how much experience one might have anyone could also make a mistake like, getting lost, tangled etc...
I think reserving more air is the way to go.

Well said!!!!

[phillip1]

Truthfully Rob, I've yet to see a cave death that could have been prevented by 200psi more gas. That's really what it all boils down to for me...



Really what this comes to for me at least, is that thinking 100, 200, or 300psi is going to safe a life is not a theory I buy into. .

I do not think that reserving 200-300psi of extra gas is any kind of theory at all, but it sure as hell would help and could make the difference if I or anyone else should ever be in a bad situation and need it.
And especially since it does not hinder in any significant way any dive to reserve that extra amount.

I know that if (god forbid) I was almost OOA and I still had 200-300 psi left I would at least be looking at my gauges and still have a little time left to save myself as opposed to dead.

[jj1987]

I do not think that reserving 200-300psi of extra gas is any kind of theory at all, but it sure as hell would help and could make the difference if I or anyone else should ever be in a bad situation and need it.
And especially since it does not hinder in any significant way any dive to reserve that extra amount.

I know that if (god forbid) I was almost OOA and I still had 200-300 psi left I would at least be looking at my gauges and still have a little time left to save myself as opposed to dead.
I agree that 200-300 psi would be nice if you were almost OOA.

This thread has flipped between buddy diving and solo, so I just wanted to point out one thing, I think it's a rather obvious fact, but I'm not sure we're all on the same page here-
Let's think about how much reserve is built in just diving manifold doubles in a 2 man team....we'll start with 3600psi. At max pen, diver A has 2400psi, diver B has at least 2500psi or he would have turned the dive. Diver A has a gas leak, which even the worst of those was proven to take about 90 seconds to drain a LP95 at eagles nest. Let's assume the relationship between time and lost gas per second is linear (it's somewhat logarithmic), and the diver takes 45 seconds to shut down (this is 3x the time GUE allows, I'm not sure what UTD's standards are, and I don't think NACD/NSS-CDS have any) the worst possible gas leak, a LP hose. Diver A has saved enough gas to exit the cave, minus the inaccessible 100psi due to regulator working pressures. Diver B still has 2400psi to exit the cave. Between the two of them each diver has 1.5x the gas that they used to enter the cave, and they wont be looking around (saves time), wont be pulling reels (saves time), will possibly have at least some flow at their back (saves time). Diving 1/3rds with a buddy is giving you a substantial amount of conservatism compared to backing off 1/3rds by 300psi when solo. Solo with 1/3rds-300psi gives you about 1.125x the gas required to exit the cave, vs 1.5x with a buddy without backing off 1/3rds at all... I just wanted to make sure we're all talking about the same thing here...

If backing off 200-300psi was referring to solo, I think that's certainly dangerous after reading this and I can see where you guys are coming from! I think we were just misunderstanding each other... :)

[Spd 135]

I think Spare Air sales are about to go up :)

[DA Aquamaster]

This thread focuses on ONE way to manage risk. I personally don't believe the recent cave deaths that I've read about would be prevented with a few 100 psi of extra gas.


Truthfully Rob, I've yet to see a cave death that could have been prevented by 200psi more gas. That's really what it all boils down to for me...

2009 Devils - Multiple visual jumps and didn't even know what tunnel they were in, buddy went to the opposite side of the cave to search.
2009 Devils - Medical condition with plenty of gas
2008 Waynes World - Had a full tank and didn't realize isolator was closed.
2008 Devils - theoretically had enough gas to get home but fiddled with a breather
2008(9?)- JB Medical condition with plenty of gas
2008(9?)- JB Breather issue of some sort
2005 - Peacock 3 - single tank and I'm going to guess the castle on air?
2004 - Eagles Nest again, high END
2003 - Little River over 1000ft back at time of death
2003- Cow over 1000ft back with 2000psi of gas
2002 - Peacock medical condition
2002 - Ginnie wrong gas
2001- JB Wrong gas (13% o2 according to iucrr)
2001- Royal springs over 500ft back at time of death (if they were backmount, I don't think they could have gotten that far, but IUCRR report says that... I didn't get much past p300 in there), likely died going the wrong way, more gas would have put them further if possible.
2000- Little River 900ft from exit.

There's trends I'm putting together, but I don't care enough to hash it out on a public forum, there's so many variables in every accident that we're each going to draw our own conclusions. I'm sure there's details I missed on some of these IUCRR reports, but my own hypothesis is that even an extra 100cu ft of gas wouldn't have changed many of the deaths I've found detailed record of.

Really what this comes to for me at least, is that thinking 100, 200, or 300psi is going to safe a life is not a theory I buy into.

A list of fatal dives where gas was not a factor just shows a number of cave deaths where gas was not a causative or contributing factor - where the dead would have been dead regardless of the gas available. However, you have to be careful not to over interpret what that actually means in the larger ppopulation of all cave dives.

With regard to that populations, what a list of cave deaths will not show are the unknown number of dives that ended safely but that may have ended in a fatality had a smaller gas reserve been used.

Looking at this list as it relates to the broader population of all cave dives might lead to a hypothesis that (assuming most divers dive thirds or more conservatively than thirds) the low number of deaths related to running out of gas provides statistical support that this conservative approach to gas planning works. This would be evidenced by the observation that fatal cave dives where more gas would have made a difference are statistically very low.

In contrast, if we saw large numbers of cave diving deaths where gas was a factor, then it would suggest that commonly used gas reserves were not sufficient.

Another possible hypothesis is that once a cave diver enters certain population domains or engages in certain behaviors such as diving above your training level, diving with a medical condition, diving a rebreather, being complacent (making multiple visual jumps, etc), the data supports that there are simply far more probable causes of death than a liberal approach to gas management.

In either case, you can't just look at what has caused cave diving deaths but instead you also have to look at what prevents cave diving deaths.

That perspective takes us back to the foundations of accident analysis and the rules that were developed, but most importantly, it highlights the decline in the statistical frequency of cave diving deaths that has occurred since that time.

You have to consider that before you can accurately say that 200-300 psi would in fact NOT make a difference, as your sample by definition, does not include dives where it MAY have made a difference.

------

Consider 300 psi more gas in a set of double 130's (7.2 cu ft per 100 psi) in a cave with an average depth of 70' and a diver with a SAC of .6 CFM. That extra 300 psi / 21.6 cu ft will provide another 11.5 minutes of time at 70 ft. Given you can cover 50 feet per minute in a no flow cave without really pushing hard, that leaves you with enough "extra" gas to cover 575 feet of cave.

To put that in perspective, with 87 cu ft for a "third" and the same SAC and swim speed, that adds up to 46 minutes and about 2300 feet of penetration to thirds. If you back off only 100 psi per "third", you reduce the penetration time to 42 minutes and the distance to about 2100 ft. So you turn 200 ft closer to the exit and you have enough extra gas to cover 575 more feet. In total that is an 8 minute time advantage and a 775 ft exit distance advantage gained by turning only 100 psi earlier.

Obviously since the dive went south, you are probably not exting under ideal circumstances, but all things being equal if your exit is delayed by X minutes while you resolve whatever problem(s) came up, once you are headed out, you now have those same time and distance advantages working in your favor with that 300 psi greater reserve from turning 100 psi sooner.

Would it make a significant difference? Who knows. From a data perspective without having "close call" data from the population of non-fatal cave dives to help us quantify the issue, we can't really tell.

But none the less, despite this lack of definitive data, in light of the gas/time/distance numbers as well as what a list of diving deaths does NOT tell us, I'm personally very hesitant to say a 200-300 psi "pad" in the gas reserve is not potentially significant.

[LiteHedded]

i don't recall anyone ever dying that didn't break another rule or have some unforseen medical event in the cave. would gas have helped some of the guys on that list? yea.
but so would not doing visual jumps, not removing a rebreather in the back of the cave, checking their backup regulator and finding out their isolator was closed, diving the proper gases etc.

looking at cases and saying 'oh he died so close to that stage bottle' or 'so close to the exit' and assuming more gas is the answer is a little short sighted IMO.

having said that there's nothing wrong with bumping up your reserves. nothing at all

[phillip1]

I agree that 200-300 psi would be nice if you were almost OOA.

This thread has flipped between buddy diving and solo, so I just wanted to point out one thing, I think it's a rather obvious fact, but I'm not sure we're all on the same page here-
Let's think about how much reserve is built in just diving manifold doubles in a 2 man team....we'll start with 3600psi. At max pen, diver A has 2400psi, diver B has at least 2500psi or he would have turned the dive. Diver A has a gas leak, which even the worst of those was proven to take about 90 seconds to drain a LP95 at eagles nest. Let's assume the relationship between time and lost gas per second is linear (it's somewhat logarithmic), and the diver takes 45 seconds to shut down (this is 3x the time GUE allows, I'm not sure what UTD's standards are, and I don't think NACD/NSS-CDS have any) the worst possible gas leak, a LP hose. Diver A has saved enough gas to exit the cave, minus the inaccessible 100psi due to regulator working pressures. Diver B still has 2400psi to exit the cave. Between the two of them each diver has 1.5x the gas that they used to enter the cave, and they wont be looking around (saves time), wont be pulling reels (saves time), will possibly have at least some flow at their back (saves time). Diving 1/3rds with a buddy is giving you a substantial amount of conservatism compared to backing off 1/3rds by 300psi when solo. Solo with 1/3rds-300psi gives you about 1.125x the gas required to exit the cave, vs 1.5x with a buddy without backing off 1/3rds at all... I just wanted to make sure we're all talking about the same thing here...

If backing off 200-300psi was referring to solo, I think that's certainly dangerous after reading this and I can see where you guys are coming from! I think we were just misunderstanding each other... :)

I was not referring to solo diving that's a whole other thread, and I agree with you 100% that 200-300psi of 1/3rds is not sufficient at all in solo, I was referring to buddy diving.
Having that 200-300psi extra air could make a big difference.

I think that in the above very likely scenario you describe, if on exit something else goes wrong to further delay the swim out, say a total siltout and then getting lost a bit and losing time figuring out which way to go, or losing the line, caught in the line, the donor gets a freeflow etc.. anyway you look at it that little extra air will always help in every single situation.

I know that if I were involved in some type of emergency and was running low on air I would absolutely looooooooooooooooove the air fairy to show up and give me 10-15mins more air.

[LCF]

I think DAA's argument is a good one. If we were seeing a lot of deaths from people running out of gas, reserving a third would appear not conservative enough. Since we aren't, it appears that reserving a third is adequate, unless the majority of divers are reserving more -- which at least from this poll, they don't appear to be.

We have a rationale for thirds, which probably isn't really very valid, but it's at least a rationale. Once you throw that out, how DO you decide how much gas to hold in reserve?

[ssmdive]

I think DAA's argument is a good one. If we were seeing a lot of deaths from people running out of gas, reserving a third would appear not conservative enough. Since we aren't, it appears that reserving a third is adequate, unless the majority of divers are reserving more -- which at least from this poll, they don't appear to be.

We have a rationale for thirds, which probably isn't really very valid, but it's at least a rationale. Once you throw that out, how DO you decide how much gas to hold in reserve?

Exactly... The how much is enough and if it is not broken, don't "fix" it.

In skydiving we have two parachutes, a main and a reserve. We have found that two is fine... Yes, there are times that the second one fails as well. But it was found that a third parachute was more dangerous than the chances of the second one failing.

Also, while most say they will dive to 1/3rds.... That does not mean they *always* do it. I will dive to 1/3rds, but many of my dives are less due to meeting the original goal (traverse/circuit).

Most fatalities seem to be errors other than gas management. Which leads to my question..... Again in skydiving we print each fatality with root causes in our membership magazine. Every year they do a fatality summary. AND on some websites we discuss each accident and trend them.... Where can I find this type of data for cave diving? It is not morbid curiosity, but a valuable learning tool.

[DA Aquamaster]

Exactly... The how much is enough and if it is not broken, don't "fix" it.

In skydiving we have two parachutes, a main and a reserve. We have found that two is fine... Yes, there are times that the second one fails as well. But it was found that a third parachute was more dangerous than the chances of the second one failing.

Also, while most say they will dive to 1/3rds.... That does not mean they *always* do it. I will dive to 1/3rds, but many of my dives are less due to meeting the original goal (traverse/circuit).

Most fatalities seem to be errors other than gas management. Which leads to my question..... Again in skydiving we print each fatality with root causes in our membership magazine. Every year they do a fatality summary. AND on some websites we discuss each accident and trend them.... Where can I find this type of data for cave diving? It is not morbid curiosity, but a valuable learning tool.I think that is a key component to understanding and developing safe practices. The same type of discussion occurs in varous segments of aviation. Following an aviation accident, it make take months for a final report to be issued, but the preliminary facts are published very quickly and the entire report IS ultimately made available to the general public.

My observation in the cave community has been that it works somewhat differently. Accidents are investigated with concerted efforts to suppress any facts known early on to limit 'speculation' (with the opposite result)usually accompanied with statements that after the incident is thoroughly investigated, the findings will be distributed to the "cave community".

I am not sure who comprises the "cave community", but it is certainly not all cave divers and there is clearly no openly public method of presenting findings.

Cave diving publications will devote lots of column space to the exploration of some cave, but don't devote much if any column space to an accident report or analysis. Some accidents do show up on the IUCRR website and on occasion you can get reports from other sources (NEDU, etc), but for many of them, you never really get any final definitive information or see a formal accident report.

There is significant room for improvement and such knowledge should not be limited to investigators, safety officers and instructors but rather should be made readily available to all cave divers.

[phillip1]

I think some people misunderstood my point, I am not saying that in the accidents were divers drowned near an entrance having 200-300 psi more would have saved them, maybe they were conservative and had that extra gas but used it all, what I am saying is that it might have saved them, and that any way you look at it, having more gas no matter how much could only help in any situation.

[PfcAJ]

Then lets dives 10ths. Its more, so its better?

The answer is to not do dumb things, like not practicing basic skills (valve, s-drills, pre dive checks, etc) deep air, visual jumps, poor cylinder marking/gas switch procedures, dive shoddy equipment, being out of shape, diving past your training and/or experience, solo (since there are a lot of solo or effectively solo deaths) etc.

My goal is to stay way out of the incident pit. I don't put a foot on the banana peel. Cave diving is great, but its not worth dying over. I firmly believe and my own personal meta-analysis of every cave diving death I've ever seen, heard, or read about points to one (or more) of those above mentioned things starting the chain reaction, leading to a fatality.

[jj1987]

I think some people misunderstood my point, I am not saying that in the accidents were divers drowned near an entrance having 200-300 psi more would have saved them, maybe they were conservative and had that extra gas but used it all, what I am saying is that it might have saved them, and that any way you look at it, having more gas no matter how much could only help in any situation.
I think what they're saying, is that if the diver died without draining the tanks, or did not die within the distance 200-300ft would allow you to swim, that the 200-300 psi would have done no good.

It's just a mathematical fact. A cave around 100ft, let's say JB or Little River, a .6 sac uses 2.41 cu ft per minute which gives 6.32 minutes of gas, or roughly enough gas to swim 400ft or so in a no flow situation, or let's say 800ft in flow. If the person didn't die out of air in that last 800ft, 200-300psi would not help them.

I would love to see a list of deaths that involved only divers who were at least intro to cave, not solo diving, not making visual jumps or unmarked T's, and not diving deep air. I'm guessing it would be surprisingly small.

[phillip1]

Then lets dives 10ths. Its more, so its better?

-No, all I am saying is I add a dose of conservatism on top as 1/3rd in my opinion is not conservative enough, especially in no flow caves, counting on flow or that everything will be cool every time is not how I choose to plan my dives.

The answer is to not do dumb things, like not practicing basic skills (valve, s-drills, pre dive checks, etc) deep air, visual jumps, poor cylinder marking/gas switch procedures, dive shoddy equipment, being out of shape, diving past your training and/or experience, solo (since there are a lot of solo or effectively solo deaths) etc.

-Agreed, I practice (and so should everyone no matter how good you think you are) valve, s-drills and thoroughly pre-dive check every time I dive.

My goal is to stay way out of the incident pit. I don't put a foot on the banana peel. Cave diving is great, but its not worth dying over. I firmly believe and my own personal meta-analysis of every cave diving death I've ever seen, heard, or read about points to one (or more) of those above mentioned things starting the chain reaction, leading to a fatality.

-Agreed, but having a bit more air will always be a +

[Slüdge]

solo (since there are a lot of solo or effectively solo deaths)

Gary, if I may...

Sure, people die solo, but I've never seen it as a cause of their death. It can always be attributed to something else. Until someone dies of loneliness, I'll leave solo off the list.

(Most people that die in caves are wearing environmental suits. Let's get to the root of the problem and ban suits.)

[PfcAJ]

I agree, being alone doesn't cause it, but it sure seems to be a foot on the banana peel. Just my opinion, of course.

[RN]

From another thread here:


Remember that the thirds rule is just a guide and don't forget that the last 10 bar or so (145 PSI in foreign currency) is not available. Remember also that your safety margin may not be as safe as you like. A 5 minute delay in shallow water with big cylinders doesn't eat much into your gas reserves but in a tight sump with little cylinders or at depth you've got problems. One CDG diver lost his life exactly this way and the CDG now teaches added conservatism.

Mike Boon, inventor of sidemount formulated he first gas management rule in the 1960's of only using 1/2 or your air supply for the entire dive.

[phillip1]

I read the CDG manual a while ago and they teach a very conservative approach that I agree with.
They start by taking of 10bar for the valve, (as you cannot breath if there is 10 bar in a tank, not enough pressure to work the reg), that is before they even begin to do the gas calculations for a dive.

If you had 200bar you actually can only use 190bar, so if you are diving to 134 (thirds) you are in reality diving to 124 (a bit past thirds).
To me it really makes sense no matter what way I look at it to dive thirds +20bar and adds a bit of conservatism on top, it can never hurt or at the very least I am not ever diving past true thirds.

What I found interesting when I read the CDG manual at the time is why only the CDG teaches this about actual working tank pressure and taking off 10bar for the valve, no other training agency does (I think), I have read other training manuals and none mentioned this.

[FW]

What I found interesting when I read the CDG manual at the time is why only the CDG teaches this about actual working tank pressure and taking off 10bar for the valve, no other training agency does (I think), I have read other training manuals and none mentioned this.
I was taught that in my first OW class, over 40 years ago. It shouldn't be necessary to teach it in a cave class, if it is still taught in OW. Most dive boat operators insist that you have 500psi (34bar) left in your tanks when you surface.

[Slüdge]

as you cannot breath if there is 10 bar in a tank, not enough pressure to work the reg

This is a misconception. I've breathed a cylinder down to less than 50psi, or 3bar. It's just not as easy to breathe.

[LiteHedded]

I was taught that in my first OW class, over 40 years ago. It shouldn't be necessary to teach it in a cave class, if it is still taught in OW. Most dive boat operators insist that you have 500psi (34bar) left in your tanks when you surface.

it's funny because typically no one on the boat can do the calculations to make that happen

[DA Aquamaster]

I read the CDG manual a while ago and they teach a very conservative approach that I agree with.
They start by taking of 10bar for the valve, (as you cannot breath if there is 10 bar in a tank, not enough pressure to work the reg), that is before they even begin to do the gas calculations for a dive.

If you had 200bar you actually can only use 190bar, so if you are diving to 134 (thirds) you are in reality diving to 124 (a bit past thirds).
To me it really makes sense no matter what way I look at it to dive thirds +20bar and adds a bit of conservatism on top, it can never hurt or at the very least I am not ever diving past true thirds.

What I found interesting when I read the CDG manual at the time is why only the CDG teaches this about actual working tank pressure and taking off 10bar for the valve, no other training agency does (I think), I have read other training manuals and none mentioned this.


This is a misconception. I've breathed a cylinder down to less than 50psi, or 3bar. It's just not as easy to breathe.Sludge is correct, particularlary with a high performance balanced piston regulator. You can breathe the tank down to almost nothing, it just gets harder to breath once the pressure drops below the normal IP. The same thing will be true with most high performance diaphragm regs as the seat carrier is upstream of the orifice, and any imperfections in balancing will result in less downstream force holding the seat on the orifice.

The only design where it might be an issue is with unbalanced flow by piston designs, and I don't know any serious technical divers who use them for back gas.

Another issue of greater importance is the accuracy of the SPG. It is not uncommon for an SPGs to hit the peg with 100-150 psi of pressure still left in the tank. SPGs are not guarenteed to be equally accurate over their entire range. Ideally in terms of turn pressures, you want a gauge that is accurate in the middle of the scale around 2400 psi and the accuracy at the low end of the scale does not matter all that much. Again in terms of thirds, errors at the high end of the scale are only problematic if the SPG reads 300 psi high and causes you to ad another 100 psi in each third. Any less of an error, and you are rounding down anyway and will absorb any error from a high reading.

At the low end of the scale, if an SPG reaches zero psi in the tank with the needle still off the pin, then its obvious to both the factory technician and to the diver that the gauge is fubar, since the gauge would show something greater than zero when to attached to a tank. In contrast, if the gauge is reading 100-200 psi too low at the low end of the scale, no one notices and it is in effect a built in reserve. If you ever bother to check your SPG reading before you pressurize the reg, the odds are then that zero at worst really means "0" and best case may mean 100-200 psi left in the tank.

I have made a point to breathe tanks dry with reg and SPG attached to see how low I can breathe the reg and determine if there is any error on the low end of the scale. I have often found the reg will keep delivering gas on or near the surface for a few minutes after the gauge reads "0".

I suspect most agencies don't promote the "take X pressure off the top for the valve" as most agencies realize that amount varies with the reg and the SPG, and that in most cases, any unusable gas in the tank will be more than compensated for by SPG error at the low end of the range.

I do want to know that turn pressure is really the turn pressure, so I do check my SPGs for accuracy at the middle of the range on an annual basis and will reject an SPG that reads more than 50 psi above or more than 100 psi below the correct pressure at pressures around 2400 psi.

The average range of error out of 10 SPGs I own is +/- 50 psi and I have had only two I rejected over the last several years - one for reading too low at 2400 psi and one where the needle stopped going to zero after several years in service.

[phillip1]

I stand corrected, I do not remember my OW class but I don't recal them teaching about the almost empty tank thing.
I do not think you could breath at 10mtrs with 10bar or could you.

I think having a bit more air will always be better, I do not dive to thirds and I will never do a visual either.

[Slüdge]

I do not think you could breath at 10mtrs with 10bar or could you.

I generally breathe a stage only and reserve backgas for emergency. This gets me an hour most of the time.

Once, several years ago, we were diving Devil's and were about 75 minutes in as we were exiting the Lips. My stage was down to 300psi so I went to backgas. When we got to the Pyle stop (where the tunnel makes a 90° left at d50' in the Eye) I went back to the stage to see how far it would get me. I was in the bottom of the well (d20') when it got really hard to breathe. You know, like a Poseidon. So I finished out on backgas and when I got back to the car I put an IP gauge on it and it read just below 50psi.

(You like that, Forrest? :rollguy)

[Meister481]

This is a misconception. I've breathed a cylinder down to less than 50psi, or 3bar. It's just not as easy to breathe.

You can get them lower if you take your breath VERY slowly.

I NEVER dive solo, Al is with me always. :smt102

IMO (they're all opinions unless you have numbers to back it up) solo diving would have a much lower accident rate than buddy teams due to the experience level of most solo divers I know, as well as the fact that there is only 1 diver to have an issue, medical, gear or otherwise.

The same can be said for the past deaths, they were diving in a buddy team so that must be the root cause. We should look at the cause of the problem instead of the number of divers in the team.