No Limit verses Remaining Bottom Time (RBT)
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Net Doc, DiveNav does have a Galileo Sol Simulator for your phone, and a course. Because the basic functions of the Sol duplicates the Luna there is not a separate one for the Luna. The course will cover everything about the Luna, but also adds the more advanced functions of the Sol.
To the OP, I forgot to say that I used DiveNav's simulator and course for the Sol and it was great!
I do have a couple of comments re the 1.6 Po2. My PADI Nitrox training set the limits for recreational nitrox as primary gas at depth as not exceeding 1.4 but allowing 1.6 only if it was an absolute life-threatening emergency or rescue situation, for a short time, and there was no alternative. Setting 1.6 as the regular limit is outside the training standards, which is something not recommended here, I believe?
Again, there are reasons for this. My course materials, and the other reading I did, indicated the following:
Po2 1.2 or lower, no incidents of ox tox
Po2 1.4 or lower so few as to not even count, statistically
P02 1.4 to 1.6: documented incidents of ox tox, enough to create a "real" and not illusory statistical risk
Po2 over 1.6: Vast majority of ox tox takes place here, and you are at the greatest risk of incident, documented.
None of this means that "you will die" at 1.6. Overall, incidents of ox tox are very rare even at 1.6. Statistically, you are not in a high certainty of a bad outcome, you are only at the highest risk of a rare bad outcome.
However, given the severity of the outcome--ox tox at depth is pretty universally seen as a death sentence by drowning, it as an outcome that you want to minimize as close to zero as possible. Hence, the training limit of 1.4 under the conditions discussed above.
Technical divers have a different situation. I highly respect the knowledge shown by the tech divers posting here, but I think that is a case of too much knowledge being dangerous for the OP, with only 50 dives, and not a full understanding of Po2.
Yes, there are instances where po2s of 1.6 or even higher are called for:
1. Medical emergencies calling for chamber treatment. The high Po2 is needed to get the nitrogen out, and mitigate actual acute symptoms of DCS might justify the risk of ox tox. I would also add that ox tox in a chamber with medical supervision is manageable, does not result in drowning, and is not nearly the type of outcome that must be guarded against when actually diving.
2. Extreme decompression diving. Technical divers might use po2 at 1.6f for 20 or 10 foot stops on pure or high percentage o2 mixes to handle the extreme nitrogen off-gassing needs of their bodies as a result of long exposure. Here, the need for efficient decompression and prevention of DCS, the reduced time underwater, the need to carry less gas due to efficient decompression, are all balanced against the remote risk of ox tox. In addition, the high po2 is used on deco stops and not at depth, so the surface can be reached in the event of a seizure with a better chance of survival, especially with attentive team members close by. Also, most tech divers I spoke to try to stay near or at 1.6, and so at the lowest end of the risk range, and also do it when not engaging in strenuous effort (which has some indication of increasing risk of ox tox). Tech divers make this very limited choice based on extensive training.
BUT, I do not believe these particular situations are any basis for telling a rec nitrox diver that "1.6 is OK at depth" and a that warning to stick with 1.4 is just overblown hysteria.
By the way, where I dive, there are rec nitrox divers who routinely set their computers at 1.6 and dive rich mixes all the way to the MOD's for the max time allowed, or even beyond (say, diving 36% to 120fsw) based on that calculation. Their rationale, "been doing it for years and nothing has happened to me or anyone I know." They are confusing the overall rarity of ox tox with "immunity" from risk. This is a classic human self-deception. A bad outcome is statistically rare, so you (and others emulating you) engage in the risky conduct many times with (as predicted statistically) no bad result. Everyone then thinks they are immune, and keep doing the risky conduct . Eventually, though, someone will have that bad outcome (that is, after all, how the statistics come to be). They don't seem to realize they are in the group of highest risk. I decline to join them.
To the OP, I forgot to say that I used DiveNav's simulator and course for the Sol and it was great!
I do have a couple of comments re the 1.6 Po2. My PADI Nitrox training set the limits for recreational nitrox as primary gas at depth as not exceeding 1.4 but allowing 1.6 only if it was an absolute life-threatening emergency or rescue situation, for a short time, and there was no alternative. Setting 1.6 as the regular limit is outside the training standards, which is something not recommended here, I believe?
Again, there are reasons for this. My course materials, and the other reading I did, indicated the following:
Po2 1.2 or lower, no incidents of ox tox
Po2 1.4 or lower so few as to not even count, statistically
P02 1.4 to 1.6: documented incidents of ox tox, enough to create a "real" and not illusory statistical risk
Po2 over 1.6: Vast majority of ox tox takes place here, and you are at the greatest risk of incident, documented.
None of this means that "you will die" at 1.6. Overall, incidents of ox tox are very rare even at 1.6. Statistically, you are not in a high certainty of a bad outcome, you are only at the highest risk of a rare bad outcome.
However, given the severity of the outcome--ox tox at depth is pretty universally seen as a death sentence by drowning, it as an outcome that you want to minimize as close to zero as possible. Hence, the training limit of 1.4 under the conditions discussed above.
Technical divers have a different situation. I highly respect the knowledge shown by the tech divers posting here, but I think that is a case of too much knowledge being dangerous for the OP, with only 50 dives, and not a full understanding of Po2.
Yes, there are instances where po2s of 1.6 or even higher are called for:
1. Medical emergencies calling for chamber treatment. The high Po2 is needed to get the nitrogen out, and mitigate actual acute symptoms of DCS might justify the risk of ox tox. I would also add that ox tox in a chamber with medical supervision is manageable, does not result in drowning, and is not nearly the type of outcome that must be guarded against when actually diving.
2. Extreme decompression diving. Technical divers might use po2 at 1.6f for 20 or 10 foot stops on pure or high percentage o2 mixes to handle the extreme nitrogen off-gassing needs of their bodies as a result of long exposure. Here, the need for efficient decompression and prevention of DCS, the reduced time underwater, the need to carry less gas due to efficient decompression, are all balanced against the remote risk of ox tox. In addition, the high po2 is used on deco stops and not at depth, so the surface can be reached in the event of a seizure with a better chance of survival, especially with attentive team members close by. Also, most tech divers I spoke to try to stay near or at 1.6, and so at the lowest end of the risk range, and also do it when not engaging in strenuous effort (which has some indication of increasing risk of ox tox). Tech divers make this very limited choice based on extensive training.
BUT, I do not believe these particular situations are any basis for telling a rec nitrox diver that "1.6 is OK at depth" and a that warning to stick with 1.4 is just overblown hysteria.
By the way, where I dive, there are rec nitrox divers who routinely set their computers at 1.6 and dive rich mixes all the way to the MOD's for the max time allowed, or even beyond (say, diving 36% to 120fsw) based on that calculation. Their rationale, "been doing it for years and nothing has happened to me or anyone I know." They are confusing the overall rarity of ox tox with "immunity" from risk. This is a classic human self-deception. A bad outcome is statistically rare, so you (and others emulating you) engage in the risky conduct many times with (as predicted statistically) no bad result. Everyone then thinks they are immune, and keep doing the risky conduct . Eventually, though, someone will have that bad outcome (that is, after all, how the statistics come to be). They don't seem to realize they are in the group of highest risk. I decline to join them.
The Chairman
Chairman of the Board
Guy, just because you set your PDC at 1.6 does not mean you're going to dive that depth. I hate it when my alarm goes off when I get close, so I honor my MOD which is consistent to 1.4 but set my PDC to 1.6.
Thanks for the info on the Sol being so similar. I knew he had a solution.
Thanks for the info on the Sol being so similar. I knew he had a solution.
Yes, well that's a different issue. Though probably as pervasive or more so.
I recall a guy who once dove on the boat I crewed on. He had two computers: one for the first dive and one for the second. When asked why, he said "This one is a piece of crap... it always beeps at me at the end of the second dive telling me I'm in deco. Obviously that's impossible because the depth and time was the same as the first dive!"
There's a reason he only dove with us ONCE.
Guy, just because you set your PDC at 1.6 does not mean you're going to dive that depth. I hate it when my alarm goes off when I get close, so I honor my MOD which is consistent to 1.4 but set my PDC to 1.6.
Thanks for the info on the Sol being so similar. I knew he had a solution.
Yeah, I hate alarms, too. I can set mine to give only a visual, so if I exceed 1.4 the screen gives a box that says "High PO2" in inverted colors (white on black background) but no beeping. I just like setting to 1.4 especially if I am going deep, so I don't have to mentally compensate. Your system is fine as you have mastery of dive knowledge and of your computer. Not sure the OP is quite there, yet.
dumpsterDiver
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I few years ago... I told a guy to RTFM on this board and i was punished.. I think I may have been banned for a month. the guy was asking how to set his oxygen mix on his computer -- I was slammed for it.. I think I was told these kinds of comments had absolutely no place in a basic forum discussion.
I'm glad that the board seems to becoming a little more pragmatic.
I notice other drifting in etiquette as well recently: Last week , a young guy is accidentally speared through his brain stem and his parents donate his organs a few days later - the jokes and comments about Darwin fly onto the screen.
I remember a few years ago when a moderator (who was an instructor) died in 10 feet of water when scuba diving because she ran out of air by herself and could not make it to the surface. I don't remember too many jokes or "Darwin" comments on that thread.. Even though she was entirely responsible for her death and the poor guy whose was pithed, simply made the mistake of being in the wrong place at the wrong time. I guess this is a good thing.
I'm glad that the board seems to becoming a little more pragmatic.
I notice other drifting in etiquette as well recently: Last week , a young guy is accidentally speared through his brain stem and his parents donate his organs a few days later - the jokes and comments about Darwin fly onto the screen.
I remember a few years ago when a moderator (who was an instructor) died in 10 feet of water when scuba diving because she ran out of air by herself and could not make it to the surface. I don't remember too many jokes or "Darwin" comments on that thread.. Even though she was entirely responsible for her death and the poor guy whose was pithed, simply made the mistake of being in the wrong place at the wrong time. I guess this is a good thing.
R
redacted
Guest
Did you provide a link? It does make a difference.
---------- Post added July 14th, 2015 at 06:11 PM ----------
Sometimes, it is the thought that counts.
Basking Ridge Diver
Contributor
Not so sure it is a good thing... but I am glad someone had the balls to bring it up...
eelnoraa
Contributor
If OW or AOW diver diving air in single tank, to 57m, hitting PPO2 of 1.4 is the least of all the problems I see here.
---------- Post added July 14th, 2015 at 05:10 PM ----------
I actually see a bigger problem here. How was OW conduct these days? There should at least some amount of gas planning, NDL understand (based on table), PPO2 mention? These should be the most important topics in OW. If these were covered, how would anyone confused between gas remaining, NDL vs PPO2 setting? Not to mention the Divemaster is the one that changing PPo2 alarm setting in the case RBT alarm went off. what is wrong in the dive industry!!!
phoenix31tt
Contributor
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