Since dives get canceled and I do not always know ahead of time what depth I usually fill with 30%. Gives me max of 1.3 at likely sites and I am usually diving 1.2 - 1.3. On the rare deeper dive I will dive 28% to keep it at or below1.3.
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I am not sure I agree with the statement, as written. I do agree, that not only PPO2, but time as well factor into the overall risk of untoward events. But, if you hold other factors constant - e.g. time - then PPO2 becomes a controlling variable. If you are at a given depth, for a given time, your risk is greater with higher PPO2 (e.g. 1.6 vs 1.4). Of course, if the risk of an event, say a generalized tonic-clonic seizure, increases from only 0.01% to 0.02%, many would say the risk is trivial, even though it has doubled. And, that may be the basis for the statement the change im risk is so small as to be almost unmeasurable. But, as TSandM pointed out: 'You can survive the bends. You are highly unlikely to survive an oxygen seizure.' A generalized seizure at 130 ft, even if it was very unlikely to occur before it actually did, creates a scenario which some would describe as, 'It sucks to be you'.This point stuck out at me - "Please note: There is no more danger . . . . Would I be allowed to dive 30% at 1.5 or is that pushing the limits? . . . . So I am wondering do most folks dive 1.4 for conservationism or is the article above misleading?
Have you heard the bit about better to be on the boat wishing you were in the water than in the water wishing you were on the boat?
Now, where this really is something I'm passionate about is if you're regularly diving below 100fsw, you should have some sort of decompression training, whether on O2 or back gas doesn't matter, but without it you are cutting everything far too close with NDL's, certainly on repetitive dives.
Perhaps all the diving agencies should include couple of pages on decompression theory in their OW manuals.Agreed, at a minimum some "contingency familiarity." How often do you see a recreational diver get back on the boat freaking out because their computer gave them a 4min stop instead of a 3min stop "I went into deco.. I went into deco... will I die?!?" Worse, of course would be the person who gets hit with more unexpected deco than they have gas to handle.
I find with many students that a simple example of what "just a few more minutes" on the bottom can mean in a deco scenario. I'd point out to the OP, for instance, that if you planned to spend 10min at 130ft you're still within NDL, and V-Planner says you'd need 58cf of gas. However, if you got distracted while trying to get that lobster out of a hole and spent 12min at 130ft you've now got 7min of deco and need 75cf of gas. How about another 2min? Now you're looking at 10min of deco and 85ft of gas. A real problem if you're diving an 80cf tank. Because they have zero familiarity with deco, most students are shocked to learn that 2 extra minutes on the bottom means 7 minutes of deco.
As my tech instructor (Wayne from DiveSeekers) drilled into us: "Schedule. Schedule. Schedule."
Perhaps all the diving agencies should include couple of pages on decompression theory in their OW manuals.
Perhaps all the diving agencies should include couple of pages on decompression theory in their OW manuals.