OC has less deco than CCR below 200'?

[spatman]

from this thread:

Below 200', OC and CCR dive times tend to equalize, and, as a matter of fact- OC tends to have less deco, the deeper one dives.

why is that? i would think the variable PO2 would benefit CCR divers no matter what depth.

[CaptnJack]

OC gets to run a low ppO2 on the bottom then "toggle" it higher with gas switches on ascent. And reduce the inspired inert with those swithes too. We end up averaging 1.2-ish but its much lower on the bottom and higher on ascent.

CCR tends to run a constant setpoint which can't be bumped up lest the O2 limits get exceeded. And only very rarely switch diluents and eliminate an inert entirely which is very common on OC.

Net, CCR generally has less (or no) deco recreationally and up to 1 deco gas, but once you add 2+ deco gases OC is generally faster. Its a good thing CCR is warmer, they can tolerate the extra time!

[BDub]

We'll average 1.2 on the bottom, but spike the PO2 when we switch to deco gas.

So, on a 200' dive, we'll average 1.2 on the bottom, then when we get to 70', we'll spike it to 1.6 when we switch to 50%, getting off the helium as well. Then, when we get to 20' we'll spike it to 1.6 again when we switch to O2.

Someone more knowledgeable than me will chime in, but on a ccr, you're running a constant PO2, so you don't get the spikes on deco.

[spatman]

but if you fly the CCR manually, why can't you basically do the same PO2 levels as an OC diver? why not run a 1.2 setpoint at depth and then spike your mix to 1.6 or thereabouts?

is it just conservatism about O2 loading/toxicity that keeps ccr divers from spiking their PO2?

[CaptnJack]

but if you fly the CCR manually, why can't you basically do the same PO2 levels as an OC diver? why not run a 1.2 setpoint at depth and then spike your mix to 1.6 or thereabouts?

is it just conservatism about O2 loading/toxicity that keeps ccr divers from spiking their PO2?

Partially I think. One of the CCR guys will chime in. Remember you always have alot of He in the loop on CCR, even at 20ft (off gassing). Most people don't switch dils. Its hard to reduce the inspired inerts like you can with OC. Just spiking the O2 is only half the story, at deep depths (say 120ft stops) spiking the o2 only gets you a trivial decrease in inspired inerts.

Plug some dives into vplanner OC is shorter runtimes in the 200+ range.

[Joshua Smith]

Richard and Brian pretty well nailed it. On a long deco, constant p02 has less leverage than variable (OC) deco. The fact that OC divers usually see 1 or 2 "spikes" to 1.6 makes a huge difference. I'll be happy to run a CCR profile, for comparison, but, to be honest, I never took OC trimix, and I'm a little stupid as far as gas choices go. (CCR-OC bailout works a bit differently from planning a whole OC dive profile.) But I know from past experience with mixed teams that the OC guy usually clears first on deeper dives.

This all becomes a huge "decision tree", as you dive deeper. When I was limited to air diluent on my Meg, I marvelled at the vastly increased NDLs. Basically, a CCR is capable of delivering an ideal Nitrox blend at any given depth.Above 130', this seems huge. In training, we were going below 100' on every dive, 3-4 times a day, and we had plenty of time at depth for Mel to hit us with drills and make our lives miserable, before she would move us up shallower, and hit us with drills, and make our lives miserable.

After I started diving normoxic trimix (<200 fsw), the advantage was still there. But not as dramatic. When I started to do even deeper dives with OC divers, it was all gone, deco-time wise. It's a double-edged sword. The OC guy has to carry more weight, and a greater volume of gas. The CCR guy still has to carry enough OC gas to survive a complete CCR failure at the worst possible time. And accept the increased risks of a CCR. For me, it's a worthwhile trade. My SAC rate was never that great, and I love the fact that I can do ~4 hours at any depth and never run out of gas.

To answer Spatty's question: You start jamming the CNS clock badly by spiking the P02. Oc divers can get away with it, but on a CCR, it's just not a good idea. Theoretically, we could vary our setpoints throughout the dive, but, as Richard pointed out- we'd have to flush the loop, and it just adds too much complexity to an already complicated system. I'll take the trade as is, without trying to game it.

[LCF]

Being a bear of very little brain, I am confused.

If I am at 130 feet (to make the math easy) and I'm breathing a ppO2 of 1.6, my gas is 1.6 divided by 5, or 32% oxygen. The other 68% are inerts of some type. It doesn't matter whether I am on CCR or SCR or OC, I'm still breathing 68% something else.

The difference between OC and CCR is that, as you ascend, the CCR will always keep the percentage of O2 as high as you are allowed (and thus the percentage of inerts as low as feasible). Whereas on OC, you will have your ppO2 and your ppINERT both fall as you ascend, until you switch to a deco gas, where the ppO2 will spike and the ppINERT will abruptly fall. But still, no lower than the CCR gas somebody's breathing at the same depth with the identical ppO2, right?

I remember an article in Advanced Diver Magazine which I think was by Wienke, going through the decompression scheduled for an OC and CCR dive at what I believe was about 250 feet -- CCR deco was shorter by a small but definite amount. Maybe it depends on the model you are using?

[Joshua Smith]

Actually, Lynne, I think you are a bear of too much brain, if there is such a thing!

Look at it this way: On OC, even if your pp02 and ppINERT are falling on ascent- you're still inspiring a lesser f02 than a comparable CCR diver. When you switch to a deco gas, you increase the pressure gradient between your body and the new gas by a fair bit- and current decompression theories generally credit the gradient with being able to "push" inert gasses out of your body faster.

At least, that is my current state of understanding all of this voodoo. I freely admit that I trust my life to vplanner, because it seems to work very well for me.

Being a bear of very little brain, I am confused.

If I am at 130 feet (to make the math easy) and I'm breathing a ppO2 of 1.6, my gas is 1.6 divided by 5, or 32% oxygen. The other 68% are inerts of some type. It doesn't matter whether I am on CCR or SCR or OC, I'm still breathing 68% something else.

The difference between OC and CCR is that, as you ascend, the CCR will always keep the percentage of O2 as high as you are allowed (and thus the percentage of inerts as low as feasible). Whereas on OC, you will have your ppO2 and your ppINERT both fall as you ascend, until you switch to a deco gas, where the ppO2 will spike and the ppINERT will abruptly fall. But still, no lower than the CCR gas somebody's breathing at the same depth with the identical ppO2, right?

I remember an article in Advanced Diver Magazine which I think was by Wienke, going through the decompression scheduled for an OC and CCR dive at what I believe was about 250 feet -- CCR deco was shorter by a small but definite amount. Maybe it depends on the model you are using?

[CaptnJack]

and thus the percentage of inerts as low as feasible

On the long dives this is the crux. OC divers get or can create gas breaks which really mitigate pulmonary and even CNS limits (which are kinda BS as evidenced by many many divers getting out at well over 250% CNS). CCR divers don't get this spike-drop cycle (which is hard to do with a dynamic loop while sticking to the schedule & depth). And so they can't "keep the percentage of inerts as low as possible" they crash into O2 tox issues if they maxed out O2 continuously. So they run 1.2ish, or even less on really long dives.

Shallower dives CCR definitely has an advantage. Once you're into 2+ deco gases it flips the other way and OC is "faster" Although none of this is about speed anyway.

[CaptnJack]

But still, no lower than the CCR gas somebody's breathing at the same depth with the identical ppO2, right?

CCR guys cannot do 1.6 at 20ft due to offgassing (not without alot of loop flushing). So yes sometimes the OC diver can get a lower f-inerts (zero) than a CCR diver.

[Joshua Smith]

Yep- go ahead and run some 400' profiles for CCR, watch the CNS clock explode, and then come over to my house and watch CCR teams dive the Brittanic, on my DVR. I haven't done any dives that pushed my CNS too far, but I may be doing one or two in the future. I'm still playing around with the concept of air breaks vs. just letting my P02 drop, vs. just doing the dive at a constant P02. Having had the experience of spiking my P02 above 1.6 once or twice, I'm given to believe that I'm not "sensitive" to higher P02s, but....believe it or not, I'm still pretty conservative about my dive profiles.

and thus the percentage of inerts as low as feasible

On the long dives this is the crux. OC divers get or can create gas breaks which really mitigate pulmonary and even CNS limits (which are kinda BS as evidenced by many many divers getting out at well over 250% CNS). CCR divers don't get this spike-drop cycle (which is hard to do with a dynamic loop while sticking to the schedule & depth). And so they can't "keep the percentage of inerts as low as possible" they crash into O2 tox issues if they maxed out O2 continuously. So they run 1.2ish, or even less on really long dives.

Shallower dives CCR definitely has an advantage. Once you're into 2+ deco gases it flips the other way and OC is "faster" Although none of this is about speed anyway.

[Joshua Smith]

It's a real bitch to hit 1.6 at 20' on a CCR. It can be done, but nobody I know actually does it. Too much work, and you blow through a LOT of 02 doing it.

But still, no lower than the CCR gas somebody's breathing at the same depth with the identical ppO2, right?

CCR guys cannot do 1.6 at 20ft due to offgassing (not without alot of loop flushing). So yes sometimes the OC diver can get a lower f-inerts (zero) than a CCR diver.

[CaptnJack]

Yep- go ahead and run some 400' profiles for CCR, watch the CNS clock explode, and then come over to my house and watch CCR teams dive the Brittanic, on my DVR. I haven't done any dives that pushed my CNS too far, but I may be doing one or two in the future. I'm still playing around with the concept of air breaks vs. just letting my P02 drop, vs. just doing the dive at a constant P02. Having had the experience of spiking my P02 above 1.6 once or twice, I'm given to believe that I'm not "sensitive" to higher P02s, but....believe it or not, I'm still pretty conservative about my dive profiles.

and thus the percentage of inerts as low as feasible

On the long dives this is the crux. OC divers get or can create gas breaks which really mitigate pulmonary and even CNS limits (which are kinda BS as evidenced by many many divers getting out at well over 250% CNS). CCR divers don't get this spike-drop cycle (which is hard to do with a dynamic loop while sticking to the schedule & depth). And so they can't "keep the percentage of inerts as low as possible" they crash into O2 tox issues if they maxed out O2 continuously. So they run 1.2ish, or even less on really long dives.

Shallower dives CCR definitely has an advantage. Once you're into 2+ deco gases it flips the other way and OC is "faster" Although none of this is about speed anyway.

I'm a sissy not hitting 100% either. Its too cold & I'm too much a wuss to really push into the depth range where this starts to happen. The one Table 6 extended chamber ride I did I was puking near the end of every O2 session. And the attendant kept telling me nausa was not a symptom of O2 toxicity, yeah, right.

[BDub]

I'm a sissy not hitting 100% either. Its too cold & I'm too much a wuss to really push into the depth range where this starts to happen. The one Table 6 extended chamber ride I did I was puking near the end of every O2 session. And the attendant kept telling me nausa was not a symptom of O2 toxicity, yeah, right.

Cherry picker

[Joshua Smith]

Yep- go ahead and run some 400' profiles for CCR, watch the CNS clock explode, and then come over to my house and watch CCR teams dive the Brittanic, on my DVR. I haven't done any dives that pushed my CNS too far, but I may be doing one or two in the future. I'm still playing around with the concept of air breaks vs. just letting my P02 drop, vs. just doing the dive at a constant P02. Having had the experience of spiking my P02 above 1.6 once or twice, I'm given to believe that I'm not "sensitive" to higher P02s, but....believe it or not, I'm still pretty conservative about my dive profiles.

and thus the percentage of inerts as low as feasible

On the long dives this is the crux. OC divers get or can create gas breaks which really mitigate pulmonary and even CNS limits (which are kinda BS as evidenced by many many divers getting out at well over 250% CNS). CCR divers don't get this spike-drop cycle (which is hard to do with a dynamic loop while sticking to the schedule & depth). And so they can't "keep the percentage of inerts as low as possible" they crash into O2 tox issues if they maxed out O2 continuously. So they run 1.2ish, or even less on really long dives.

Shallower dives CCR definitely has an advantage. Once you're into 2+ deco gases it flips the other way and OC is "faster" Although none of this is about speed anyway.

I'm a sissy not hitting 100% either. Its too cold & I'm too much a wuss to really push into the depth range where this starts to happen. The one Table 6 extended chamber ride I did I was puking near the end of every O2 session. And the attendant kept telling me nausa was not a symptom of O2 toxicity, yeah, right.

Yeah, maybe so. But, hell-you did the Governor last year, right? That's knocking on the door of the CNS clock and running away before it answers, isn't it? Not really, I guess. I'm not making fun. I haven't been bent, yet, and I hope I never am. But I've been damn close- dives where I just *knew* I had pushed it too far. And anyone who feels like puking in the chamber has my permission to do so, whether or not it' an officially recognized "symptom" of DCS, CNS toxicity, or chlamydia.

[Joshua Smith]

I'm a sissy not hitting 100% either. Its too cold & I'm too much a wuss to really push into the depth range where this starts to happen. The one Table 6 extended chamber ride I did I was puking near the end of every O2 session. And the attendant kept telling me nausa was not a symptom of O2 toxicity, yeah, right.

Cherry picker

"Fish Sticks are not an aphrodesiac. You're thinking of deer penis."

[loanwolf]

I dive with a lot of mixed teams and CCR is always out of the water first. Most of the time the CCR divers are the first ones in and run longer bottom times than the OC will. Here is two 200' profiles the CCR is out of the water 4 min faster. Everyone I dive with as soon as we leave the bottom and start up we crank our PO2 up to a 1.5 or so and that will get you out of the water much faster. Almost every CCR diver I know other than a few does do a O2 flush at 20' and get rid of all the He in the loop and go to 100%. I do not know very many that do not. It is also a safety thing to check your cells and see if they are reading correctly.

CCR dive 20min@200'

Dec to 200ft (3) Diluent 10/50 0.70 SetPoint, 60ft/min descent.
Level 200ft 16:40 (20) Diluent 10/50 1.30 SetPoint, 74ft ead, 94ft end
Asc to 120ft (22) Diluent 10/50 1.50 SetPoint, -30ft/min ascent.
Stop at 120ft 0:20 (23) Diluent 10/50 1.50 SetPoint, 26ft ead, 62ft end
Stop at 110ft 1:00 (24) Diluent 10/50 1.50 SetPoint, 20ft ead, 58ft end
Stop at 100ft 1:00 (25) Diluent 10/50 1.50 SetPoint, 14ft ead, 53ft end
Stop at 90ft 1:00 (26) Diluent 10/50 1.50 SetPoint, 9ft ead, 49ft end
Stop at 80ft 1:00 (27) Diluent 10/50 1.50 SetPoint, 3ft ead, 44ft end
Stop at 70ft 1:00 (28) Diluent 10/50 1.50 SetPoint, 0ft ead, 40ft end
Stop at 60ft 1:00 (29) Diluent 10/50 1.50 SetPoint, 0ft ead, 35ft end
Stop at 50ft 2:00 (31) Diluent 10/50 1.50 SetPoint, 0ft ead, 31ft end
Stop at 40ft 3:00 (34) Diluent 10/50 1.50 SetPoint, 0ft ead, 27ft end
Stop at 30ft 3:00 (37) Diluent 10/50 1.50 SetPoint, 0ft ead, 22ft end
Stop at 20ft 13:00 (50) Diluent 10/50 1.50 SetPoint, 0ft ead, 18ft end
Surface (50) Diluent 10/50 -30ft/min ascent.

Off gassing starts at 141.5ft

OTU's this dive: 81
CNS Total: 35.2%

OC dive 20min@200'

Dec to 200ft (3) Trimix 17/55 60ft/min descent.
Level 200ft 16:40 (20) Trimix 17/55 1.20 ppO2, 50ft ead, 72ft end
Asc to 190ft (20) Trimix 17/55 -30ft/min ascent.
Asc to 120ft (22) Trimix 20/40 -30ft/min ascent.
Stop at 120ft 0:20 (23) Trimix 20/40 0.93 ppO2, 44ft ead, 59ft end
Stop at 110ft 1:00 (24) Trimix 20/40 0.87 ppO2, 39ft ead, 53ft end
Stop at 100ft 1:00 (25) Trimix 20/40 0.80 ppO2, 34ft ead, 47ft end
Stop at 90ft 1:00 (26) Trimix 20/40 0.74 ppO2, 29ft ead, 41ft end
Stop at 80ft 1:00 (27) Trimix 20/40 0.68 ppO2, 24ft ead, 35ft end
Stop at 70ft 1:00 (28) Nitrox 50 1.56 ppO2, 32ft ead
Stop at 60ft 2:00 (30) Nitrox 50 1.41 ppO2, 26ft ead
Stop at 50ft 2:00 (32) Nitrox 50 1.26 ppO2, 20ft ead
Stop at 40ft 3:00 (35) Nitrox 50 1.10 ppO2, 13ft ead
Stop at 30ft 4:00 (39) Nitrox 50 0.95 ppO2, 7ft ead
Stop at 20ft 15:00 (54) Oxygen 1.60 ppO2, 0ft ead
Surface (54) Oxygen -30ft/min ascent.

Off gassing starts at 153.1ft

OTU's this dive: 75
CNS Total: 49.6%

93.2 cu ft Trimix 17/55
22.1 cu ft Trimix 20/40
19.4 cu ft Nitrox 50
17.1 cu ft Oxygen
151.9 cu ft TOTAL


No mater how you run the profiles the CCR is almost all the time going to get out before OC. And that goes up exponentially as you go deeper and longer. Now you change the bottom time on these profiles to 30min and it even gets much farther apart, 74 min for CCR and 91 min for OC.

[BDub]

I'm a sissy not hitting 100% either. Its too cold & I'm too much a wuss to really push into the depth range where this starts to happen. The one Table 6 extended chamber ride I did I was puking near the end of every O2 session. And the attendant kept telling me nausa was not a symptom of O2 toxicity, yeah, right.

Cherry picker

"Fish Sticks are not an aphrodesiac. You're thinking of deer penis."

The rest of the story has has been censored due to inappropriosity

[CaptnJack]

Dec to 200ft (3) Trimix 17/55 60ft/min descent.
Level 200ft 16:40 (20) Trimix 17/55 1.20 ppO2, 50ft ead, 72ft end
Asc to 190ft (20) Trimix 17/55 -30ft/min ascent.
Asc to 120ft (22) Trimix 20/40 -30ft/min ascent.
Stop at 120ft 0:20 (23) Trimix 20/40 0.93 ppO2, 44ft ead, 59ft end
Stop at 110ft 1:00 (24) Trimix 20/40 0.87 ppO2, 39ft ead, 53ft end
Stop at 100ft 1:00 (25) Trimix 20/40 0.80 ppO2, 34ft ead, 47ft end
Stop at 90ft 1:00 (26) Trimix 20/40 0.74 ppO2, 29ft ead, 41ft end
Stop at 80ft 1:00 (27) Trimix 20/40 0.68 ppO2, 24ft ead, 35ft end
Stop at 70ft 1:00 (28) Nitrox 50 1.56 ppO2, 32ft ead
Stop at 60ft 2:00 (30) Nitrox 50 1.41 ppO2, 26ft ead
Stop at 50ft 2:00 (32) Nitrox 50 1.26 ppO2, 20ft ead
Stop at 40ft 3:00 (35) Nitrox 50 1.10 ppO2, 13ft ead
Stop at 30ft 4:00 (39) Nitrox 50 0.95 ppO2, 7ft ead
Stop at 20ft 15:00 (54) Oxygen 1.60 ppO2, 0ft ead
Surface (54) Oxygen -30ft/min ascent.

Off gassing starts at 153.1ft

OTU's this dive: 75
CNS Total: 49.6%

93.2 cu ft Trimix 17/55
22.1 cu ft Trimix 20/40
19.4 cu ft Nitrox 50
17.1 cu ft Oxygen
151.9 cu ft TOTAL

Even though its only 200ft, this has got to be one of the craziest 200ft gas selections I've ever seen. We do this on 18/45, EAN50 and O2. And

[CaptnJack]

I'm a sissy not hitting 100% either. Its too cold & I'm too much a wuss to really push into the depth range where this starts to happen. The one Table 6 extended chamber ride I did I was puking near the end of every O2 session. And the attendant kept telling me nausa was not a symptom of O2 toxicity, yeah, right.

Cherry picker

"Fish Sticks are not an aphrodesiac. You're thinking of deer penis."

The rest of the story has has been censored due to inappropriosity

TWSS!

[loanwolf]

Dec to 200ft (3) Trimix 17/55 60ft/min descent.
Level 200ft 16:40 (20) Trimix 17/55 1.20 ppO2, 50ft ead, 72ft end
Asc to 190ft (20) Trimix 17/55 -30ft/min ascent.
Asc to 120ft (22) Trimix 20/40 -30ft/min ascent.
Stop at 120ft 0:20 (23) Trimix 20/40 0.93 ppO2, 44ft ead, 59ft end
Stop at 110ft 1:00 (24) Trimix 20/40 0.87 ppO2, 39ft ead, 53ft end
Stop at 100ft 1:00 (25) Trimix 20/40 0.80 ppO2, 34ft ead, 47ft end
Stop at 90ft 1:00 (26) Trimix 20/40 0.74 ppO2, 29ft ead, 41ft end
Stop at 80ft 1:00 (27) Trimix 20/40 0.68 ppO2, 24ft ead, 35ft end
Stop at 70ft 1:00 (28) Nitrox 50 1.56 ppO2, 32ft ead
Stop at 60ft 2:00 (30) Nitrox 50 1.41 ppO2, 26ft ead
Stop at 50ft 2:00 (32) Nitrox 50 1.26 ppO2, 20ft ead
Stop at 40ft 3:00 (35) Nitrox 50 1.10 ppO2, 13ft ead
Stop at 30ft 4:00 (39) Nitrox 50 0.95 ppO2, 7ft ead
Stop at 20ft 15:00 (54) Oxygen 1.60 ppO2, 0ft ead
Surface (54) Oxygen -30ft/min ascent.

Off gassing starts at 153.1ft

OTU's this dive: 75
CNS Total: 49.6%

93.2 cu ft Trimix 17/55
22.1 cu ft Trimix 20/40
19.4 cu ft Nitrox 50
17.1 cu ft Oxygen
151.9 cu ft TOTAL

Even though its only 200ft, this has got to be one of the craziest 200ft gas selections I've ever seen. We do this on 18/45, EAN50 and O2. And

Whoops you are right the 20/40 should not be thier. Still 54 min



Dec to 200ft (3) Trimix 17/35 60ft/min descent.
Level 200ft 16:40 (20) Trimix 17/35 1.20 ppO2, 109ft ead, 118ft end
Asc to 120ft (22) Trimix 17/35 -30ft/min ascent.
Stop at 120ft 0:20 (23) Trimix 17/35 0.79 ppO2, 60ft ead, 66ft end
Stop at 110ft 1:00 (24) Trimix 17/35 0.74 ppO2, 54ft ead, 60ft end
Stop at 100ft 1:00 (25) Trimix 17/35 0.68 ppO2, 48ft ead, 53ft end
Stop at 90ft 1:00 (26) Trimix 17/35 0.63 ppO2, 42ft ead, 47ft end
Stop at 80ft 2:00 (28) Trimix 17/35 0.58 ppO2, 36ft ead, 40ft end
Stop at 70ft 2:00 (30) Nitrox 50 1.56 ppO2, 32ft ead
Stop at 60ft 1:00 (31) Nitrox 50 1.41 ppO2, 26ft ead
Stop at 50ft 2:00 (33) Nitrox 50 1.26 ppO2, 20ft ead
Stop at 40ft 3:00 (36) Nitrox 50 1.10 ppO2, 13ft ead
Stop at 30ft 4:00 (40) Nitrox 50 0.95 ppO2, 7ft ead
Stop at 20ft 14:00 (54) Oxygen 1.60 ppO2, 0ft ead
Surface (54) Oxygen -30ft/min ascent.

Off gassing starts at 151.2ft

OTU's this dive: 72
CNS Total: 47.5%

117.7 cu ft Trimix 17/35
19.7 cu ft Nitrox 50
16.0 cu ft Oxygen
153.4 cu ft TOTAL

[spatman]

When you switch to a deco gas, you increase the pressure gradient between your body and the new gas by a fair bit- and current decompression theories generally credit the gradient with being able to "push" inert gasses out of your body faster.

i think that was a missing element for me. now it makes more sense.

[Joshua Smith]

Dec to 200ft (3) Trimix 17/55 60ft/min descent.
Level 200ft 16:40 (20) Trimix 17/55 1.20 ppO2, 50ft ead, 72ft end
Asc to 190ft (20) Trimix 17/55 -30ft/min ascent.
Asc to 120ft (22) Trimix 20/40 -30ft/min ascent.
Stop at 120ft 0:20 (23) Trimix 20/40 0.93 ppO2, 44ft ead, 59ft end
Stop at 110ft 1:00 (24) Trimix 20/40 0.87 ppO2, 39ft ead, 53ft end
Stop at 100ft 1:00 (25) Trimix 20/40 0.80 ppO2, 34ft ead, 47ft end
Stop at 90ft 1:00 (26) Trimix 20/40 0.74 ppO2, 29ft ead, 41ft end
Stop at 80ft 1:00 (27) Trimix 20/40 0.68 ppO2, 24ft ead, 35ft end
Stop at 70ft 1:00 (28) Nitrox 50 1.56 ppO2, 32ft ead
Stop at 60ft 2:00 (30) Nitrox 50 1.41 ppO2, 26ft ead
Stop at 50ft 2:00 (32) Nitrox 50 1.26 ppO2, 20ft ead
Stop at 40ft 3:00 (35) Nitrox 50 1.10 ppO2, 13ft ead
Stop at 30ft 4:00 (39) Nitrox 50 0.95 ppO2, 7ft ead
Stop at 20ft 15:00 (54) Oxygen 1.60 ppO2, 0ft ead
Surface (54) Oxygen -30ft/min ascent.

Off gassing starts at 153.1ft

OTU's this dive: 75
CNS Total: 49.6%

93.2 cu ft Trimix 17/55
22.1 cu ft Trimix 20/40
19.4 cu ft Nitrox 50
17.1 cu ft Oxygen
151.9 cu ft TOTAL

Even though its only 200ft, this has got to be one of the craziest 200ft gas selections I've ever seen. We do this on 18/45, EAN50 and O2. And

Whoops you are right the 20/40 should not be thier. Still 54 min



Dec to 200ft (3) Trimix 17/35 60ft/min descent.
Level 200ft 16:40 (20) Trimix 17/35 1.20 ppO2, 109ft ead, 118ft end
Asc to 120ft (22) Trimix 17/35 -30ft/min ascent.
Stop at 120ft 0:20 (23) Trimix 17/35 0.79 ppO2, 60ft ead, 66ft end
Stop at 110ft 1:00 (24) Trimix 17/35 0.74 ppO2, 54ft ead, 60ft end
Stop at 100ft 1:00 (25) Trimix 17/35 0.68 ppO2, 48ft ead, 53ft end
Stop at 90ft 1:00 (26) Trimix 17/35 0.63 ppO2, 42ft ead, 47ft end
Stop at 80ft 2:00 (28) Trimix 17/35 0.58 ppO2, 36ft ead, 40ft end
Stop at 70ft 2:00 (30) Nitrox 50 1.56 ppO2, 32ft ead
Stop at 60ft 1:00 (31) Nitrox 50 1.41 ppO2, 26ft ead
Stop at 50ft 2:00 (33) Nitrox 50 1.26 ppO2, 20ft ead
Stop at 40ft 3:00 (36) Nitrox 50 1.10 ppO2, 13ft ead
Stop at 30ft 4:00 (40) Nitrox 50 0.95 ppO2, 7ft ead
Stop at 20ft 14:00 (54) Oxygen 1.60 ppO2, 0ft ead
Surface (54) Oxygen -30ft/min ascent.

Off gassing starts at 151.2ft

OTU's this dive: 72
CNS Total: 47.5%

117.7 cu ft Trimix 17/35
19.7 cu ft Nitrox 50
16.0 cu ft Oxygen
153.4 cu ft TOTAL

Greg: Look, man- you're in a class by yourself. You recently declared, on this site, that dives above 300 fsw "weren't really tech dives."

You also shared with us, on this site, that you spent ~650 hrs underwater last year.

ON TOP OF WHICH, you shared with us the fact that you were working with DARPA, and did 600 and 800' dives with them.


WOW.


Look, seriously- the rest of us cannot begin to compete with that kind of stuff. Who knew, when you were still diving OC, when you were DMing my CCR trimix class, that you would get a revo, a year later, and push the limits of diving so far, in such a short time? I, for one, am very impressed.

But- please don't try and raise the bar. Newbies are still newbies: and I would really hate to see anyone hurt trying to follow your example. The vast majority of human beings are not capable of doing even half of what you can do- summitting Everest without 02? Scootering from cove 1 to the fishing reef and back without surfacing? Amazing accomplishments, to be sure. But maybe, just maybe, you could be encouraging one of us "mere mortals" to push things too far.

[Joshua Smith]

When you switch to a deco gas, you increase the pressure gradient between your body and the new gas by a fair bit- and current decompression theories generally credit the gradient with being able to "push" inert gasses out of your body faster.

i think that was a missing element for me. now it makes more sense.

Well- take it for what it's worth. Deco theory is theoretical by it's very nature. And I strongly believe that it's a lot like voodoo and black magic, in the technical realm. One can do the same profile, safely, over and over again- but on the 587th dive, one might surface paralyzed from the waist down....or some such. Like it or not, the more you dive, and the deeper you go, the closer you get to being a lab rat.

I have my own theories about my profiles. The more I dive, the better I get at predicting which dives are gonna make me feel like crap when I'm done. Let's just say that an extra 10 minutes at 20' never hurt anyone. Except for when it did.

[bigsky]

can i play?
i spent the last few years being the oc token
with many ccr partners on some pretty nice dives
nothing legendary

but the admiral sampson was pretty cool

not once, EVER (as in never) did the ccr buddies clear before me
oddly, not once, EVER (as in never) did i (on oc) clear before my team
all in together
all out together
every time

maybe my numbers were a few shorter
maybe the ccr dude was a few shorter
but if your deco comes down to a 4 minute difference
and you actually believe it makes a difference
i got this bridge i have been trying to sell.......