Enough bailout O2

jcook

jcook

Doing What Works
So while doing my Cave CCR class with Deep Smeg (he's doing a write-up for it soon) I learned a very valuable lesson, bring enough bailout O2.

So we were doing a dive at Ginne Springs and I knew I would be bailing out at some point in the dive for the training. Bailing out is something I practice regularly, but when I practice it, it is usually right in from the max penetration and right out, so not much deco obligation. I know, not the smartest practice since I only will bring an AL 30 or 40 of O2. On the Ginne dive I ended up bailing out at about 3 hours and 15 minutes into the dive, I saw I had a ton on deco but I didn't really add two and two together (first screw-up). I had only brought a AL30 of O2 for deco (second screw-up), but I had 2 LP85's cave-filled with 32%. So in all my infinite wisdom, I had plenty of gas to get out. Well I had been toying around with using the Fast Bail-Out option on my X1 (I don't recommend it to anyone, unless you are about to die from a lack of bailout gas), so I had switched it to my Bailout 1 plan (third screw-up). When I bailed I switched it and looked at my deco obligation, which wasn't much, 36 minutes or so. It sent me to the 20ft stop first, no other stops on the way. Everyone else had stops at 50, 40, 30, and 20. I didn't really think about it at the time, ya I know stupid of me. By the time the other 3 guys got to the 20 ft stop, my deco had cleared but I didn't feel very well. My instructor came up to me and wanted to see how much deco I had left and showed me his VR3 which said 48 minutes. I had about ~300 psi left in my AL30 and decided to see how much deco I would have if I switched to my Bailout 2 plan. It jumped to 66 minutes, my eyes about popped out of my head since I had drained my bailout O2 bottle. This was bad, I carry dual onboard O2 on my Hammerhead to make sure if I have an O2 failure in a cave, I can deal with it. I have no way of accessing it on OC though, but it wouldn't have been enough anyways. I never thought I would need this much for deco on bailing out (ya I know fourth screw-up). Thankfully I was with 3 other people that brought O2 bottles, I ended up draining 2 AL30's and an AL40 for my deco, which ended up being about 100 minutes. There were 4 total screw-ups that I should've planned for, but I didn't. Thankfully I was with others on this dive and I learned something valuable. Also pulmonary oxygen toxicity sucks.

So the moral of the story, make sure you carry enough O2 bailout for the dives you do, not just enough bailout to get you to the exit.
 
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jptaylor9 said:
I'd be interested in a bit more feedback & why you don't recommend it?
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I would've been bent, no questions asked. It basically had me blow off 3 deco stops and send me straight to 20 ft to make sure I got out of the water as soon as possible with the least amount of gas used. I believe the Fast Bailout option is something for extreme dives where the amount of gas on hand is just enough to keep the diver alive, plus when there is a chamber in the immediate vicinity to help the person after getting bent.
 
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First - thanks for posting.

Just to clarify this was a training diving? Is it not better to assess gas usage in a training environment rather than in a cave with real deco obligation? (Sorry if i misunderstood).

In reality do you think your RMV would be higher if this was a for-real problem?

How much extra bail-out do you think you would take after this lesson?

Cheers
Matt.
 
The accepted calculation in the NF diving community is to calculate 2cuft sac to account for a possible co2 problem.
Ginnie is app 90' so let say 3 atm
so 2cuft X (3atm+1atm(surface))= 8cuft per min
avg swim speed 50' an min means 160cuft per 1000foot of penetration
therefore 2 al80's per 1000ft of penetration
also add whatever deco gas would be needed for the planned dive exit using your bail gas as bottom gas for the lenght of time to reach the exit.
Gabe
 
divingabe said:
The accepted calculation in the NF diving community is to calculate 2cuft sac to account for a possible co2 problem.
Ginnie is app 90' so let say 3 atm
so 2cuft X (3atm+1atm(surface))= 8cuft per min
avg swim speed 50' an min means 160cuft per 1000foot of penetration
therefore 2 al80's per 1000ft of penetration
also add whatever deco gas would be needed for the planned dive exit using your bail gas as bottom gas for the lenght of time to reach the exit.
Gabe
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What's NF?

For us metricated divers :-) I'm first converting to lpm...

2cfpm is 56lpm. I'd say 50lpm, so a good number to use for RMV.

90ft, 27m, 4 bar - I see you added the extra atmosphere later one. So 224lpm.

I don't know how far it was, but a full 80cf is 2250L and would last 10 minutes. Providing you could actually swim/scooter then 50 foot/min is 500 foot per 80cf.

So how far from the exit was it? Would you still use 2cfpm for the deco phase (I would).

Matt.
 
matthewoutram said:
First - thanks for posting.

Just to clarify this was a training diving? Is it not better to assess gas usage in a training environment rather than in a cave with real deco obligation? (Sorry if i misunderstood).

In reality do you think your RMV would be higher if this was a for-real problem?

How much extra bail-out do you think you would take after this lesson?

Cheers
Matt.
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Yes, for the 3rd time it was training. The training was in a cave with a real deco obligation. I was in Ginnie Springs in Florida.

Yes NF stands for North Florida.

I purposely breathed quite fast trying to raise my RMV, I swam like a bat out of hell to the exit. So no, unless it was a CO2 hit, I doubt my RMV would raise at all. I had plenty of bottom gas bailout, it was my deco bailout that I was short on.
 
jcook said:
Yes, for the 3rd time it was training. The training was in a cave with a real deco obligation. I was in Ginnie Springs in Florida.
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I asked once, because it sounded odd to me to make a non-forced bail-out in a cave with mandatory stops and call it a drill, sorry you became agitated by my clarification, it was not the intention.

I purposely breathed quite fast trying to raise my RMV, I swam like a bat out of hell to the exit. So no, unless it was a CO2 hit, I doubt my RMV would raise at all. I had plenty of bottom gas bailout, it was my deco bailout that I was short on.
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How big's an LP85 (in litres?). 1500psi or something?

I've never had a CO2 hit but I'm not sure if it is possible to swim - I guess it depends on severity.

Matt.
 
lp85 is 85cuft for 2640psi with an overfill to 3500psi it will provide 112cuft and in NF cave country it is a common overfill.
conversion to liters 1cuft=28.31l
112cuft=3170.7liters
As a note your deco gas calculations can be downsized to half of the 2cuft/min When in deco you should be at rest, so your rmv will be close to normal.
Gabe
 
divingabe said:
lp85 is 85cuft for 2640psi with an overfill to 3500psi it will provide 112cuft and in NF cave country it is a common overfill.
conversion to liters 1cuft=28.31l
112cuft=3170.7liters
As a note your deco gas calculations can be downsized to half of the 2cuft/min When in deco you should be at rest, so your rmv will be close to normal.
Gabe
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I see, we have no such concepts in the UK, so it's interesting to learn.

The OP had 1x30cf (o2) and 2xLP85 (32%). I know diddle about this cave, so I'm assuming we're on the 32% at 40m. If those LP85's are 3170L then we have 6340L available. Mostly we're going to be shallower than 40m, I should think using 15m as an average would be fine - so 2.5ata.

Using the 1cfm that's 90 minutes on the 32% plus 18 mins at 6m, 108 total.

Theoretically then just enough for the 100 min stop - was RMV higher??

This is one of the rare times I'm seeing proper RMV's being used for gas planning, so it's interesting to see why it wasn't enough.

Matt.
 
matthewoutram said:
I see, we have no such concepts in the UK, so it's interesting to learn.

The OP had 1x30cf (o2) and 2xLP85 (32%). I know diddle about this cave, so I'm assuming we're on the 32% at 40m. If those LP85's are 3170L then we have 6340L available. Mostly we're going to be shallower than 40m, I should think using 15m as an average would be fine - so 2.5ata.

Using the 1cfm that's 90 minutes on the 32% plus 18 mins at 6m, 108 total.

Theoretically then just enough for the 100 min stop - was RMV higher??

This is one of the rare times I'm seeing proper RMV's being used for gas planning, so it's interesting to see why it wasn't enough.

Matt.
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I believe JCOOK's post was to point out the need to calculate the amount of deco gas for the given dive. He had sufficient amount of gas if he used his bottom gas for his deco, but it would have added an inordinate amount of time to his deco obligation. He was with a group of divers who had O2 available so he used their gas to keep his in water time somewhat similar to the rest of the team.
It is a good practice to calculate your deco gas for an AH SHIT moment so you may exit properly without having to stay longer than necessary. I believe in planning as if diving solo even when buddying up with others and therefore bringing enough deco for the possible obligation. You never know when a problem such as seperated team and MR MURPHY comes and says HI. Of course certain dives can become overly complex with the amount of bail gas to be staged or carried in those you have to sometimes rely on your team or do several set up and clean up dives to reach your objective.
Gabe
 
divingabe said:
I believe JCOOK's post was to point out the need to calculate the amount of deco gas for the given dive. He had sufficient amount of gas if he used his bottom gas for his deco, but it would have added an inordinate amount of time to his deco obligation. He was with a group of divers who had O2 available so he used their gas to keep his in water time somewhat similar to the rest of the team.
It is a good practice to calculate your deco gas for an AH SHIT moment so you may exit properly without having to stay longer than necessary. I believe in planning as if diving solo even when buddying up with others and therefore bringing enough deco for the possible obligation. You never know when a problem such as seperated team and MR MURPHY comes and says HI. Of course certain dives can become overly complex with the amount of bail gas to be staged or carried in those you have to sometimes rely on your team or do several set up and clean up dives to reach your objective.
Gabe
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Thanks Gabe, couldn't have said it better myself.

The whole point of the post was to remind people who cave dive to bring enough deco gas, as I posed this in the Cave Diving forum. Most people only worry about the bottom gas bailout and just bring whatever for deco (I know I used to).
 
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jcook said:
Thanks Gabe, couldn't have said it better myself.

The whole point of the post was to remind people who cave dive to bring enough deco gas, as I posed this in the Cave Diving forum. Most people only worry about the bottom gas bailout and just bring whatever for deco (I know I used to).
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And very interesting is was too, and not just relevant to caves. Thanks for posting.

Matt.
 
jptaylor9 said:
Reading in a dive mag yesterday, it reported an explosion of an Ali 80 scuba cylinder in US (Florida) in an apartment, that did a lot of damage.

See: Cylinder blast kills diver - Divernet

Was it possibly a consequence of over-filling? :chin:

I'm OK to overfilling steels, but I'm not so keen on overfilling Ali's
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It was an ali40 and an old style which have been proven to have structural problems in the alloy used. It was not overfilled and used for O2.
We do not overfill ali's just steel bottles.
 
Thanks for posting! it was a great lesson to learn... I think a lot of cave divers only plan enough for the exit and neglect deco gases... you rarely see Open water divers do that as the Deco is their exit...
Having dived with Gabe.. I believe he has the Bailout calcs nailed.
How hard is it to stage an 80Cuft Ally of O2 just inside Devil's? would probably add a hug margin of safety to your bailout calcs as from experience, you're almost garanteed to go into decent deco in that cave.
 
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