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Padi Dsat
- Thread starter HybridDiver
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Rainer
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Yes! I sure do.
First, you should check out the references section of Wikipedia's Oxygen Toxicity article, here: Oxygen toxicity - Wikipedia, the free encyclopedia
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Oxygen Poisoning in Man
Oxygen Poisoning in Man
Let's also look at the extended O2 exposure charts...
1.44 0.71 % 141 min 2.3 hrs
1.46 0.74 % 135 min 2.3 hrs
1.48 0.78 % 128 min 2.1 hrs
1.5 0.83 % 120 min 2.0 hrs
1.52 0.93 % 108 min 1.8 hrs
1.54 1.04 % 96 min 1.6 hrs
1.56 1.19 % 84 min 1.4 hrs
1.58 1.47 % 68 min 1.1 hrs
1.6 2.22 % 45 min
1.62 5.00 % 20 min
1.65 6.25 % 16 min
1.67 7.69 % 13 min
1.7 10.00 % 10 min
1.72 12.50 % 8 min
1.74 20.00 % 5 min
1.77 25.00 % 4 min
1.78 31.25 % 3 min
1.8 50.00 % 2 min
1.82 100.00 % 1 min
In the first column, we have the PPO2, the second column is the "per minute %", third column is Single exposure and last column is 24 hour limit. This was C&P from a PDF document, so I apologize for the unclear formatting.
Looking at the table, I can see that as we increase our dose, we increase the risk. But time is key when executing dives beyond a PPO2 of 1.6. Our dose increases exponentially, so our time is also decreased exponentially. Can we infer that risk is increased as we reach greater PPO2? I cannot, as there is a time and dose relationship that gets factored in. If the relationship is kept in equilibrium, I have not found evidence that an extremely long exposure at 1.2 Bar or O2 is SAFER than a short exposure at 1.78. If anyone has this information, please share.
ouh ouh, did I pass your test?
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Interesting notion. The table you show below does show a nice relation between PO2 and single exposure. This table however is not a universally applicable one since:
Many experiments done were in dry chambers and there is a definite difference between wet hyperbaric PO2 and dry hyperbaric PO2 (some of those reports do mention that). I am not sure what the table is based on, but I personally would not use it as a guide for diving applications.
The exposure time at 1.4 for instance is around 145 minutes. Given above mention and the 145 minutes, an average dive of 45-50 minutes would bring a diver far from close to the max with the increased risk of CNS toxicity showing. There is a buffer between max exposure and real exposure. Bear in mind that some people are FAR more susceptible than others, this wide buffer shields the majority from the dangers. This is why I believe the recreational limit was set at 1.4. But I could be wrong.
If you follow the table one could indeed argue that there is no perceived safety benefit of PO2=1.2 vs. PO2=1.6 if one would stay within time limits. The effective use of the table would put many divers beyond a risk limit that could prove disastrous. 1.6 at depth would give little time, ascending and thus lowering PO2 would still add up and the safety margin is pretty much gone.
Yes on paper you could do working dives to and beyond higher PO2 levels than advised, but with the exponential time decrease, the safety factor decreases and risks increase.
Many experiments done were in dry chambers and there is a definite difference between wet hyperbaric PO2 and dry hyperbaric PO2 (some of those reports do mention that). I am not sure what the table is based on, but I personally would not use it as a guide for diving applications.
The exposure time at 1.4 for instance is around 145 minutes. Given above mention and the 145 minutes, an average dive of 45-50 minutes would bring a diver far from close to the max with the increased risk of CNS toxicity showing. There is a buffer between max exposure and real exposure. Bear in mind that some people are FAR more susceptible than others, this wide buffer shields the majority from the dangers. This is why I believe the recreational limit was set at 1.4. But I could be wrong.
If you follow the table one could indeed argue that there is no perceived safety benefit of PO2=1.2 vs. PO2=1.6 if one would stay within time limits. The effective use of the table would put many divers beyond a risk limit that could prove disastrous. 1.6 at depth would give little time, ascending and thus lowering PO2 would still add up and the safety margin is pretty much gone.
Yes on paper you could do working dives to and beyond higher PO2 levels than advised, but with the exponential time decrease, the safety factor decreases and risks increase.
In Europe, the limit ppO2 to 1.4 is not popular and they find the limit is too low and prefer 1.6.
Really? Where in Europe, it is a big place. What groups, type of diving?
Tomeck,
Who are those 'Europeans'? It is such a broad concept. I was certified in the UK , lived there for 10 years, lived in the Netherlands and Germany (and some other places) for 17 years, dove all over the place. Never have I encountered 'those Europeans' who systematically dive beyond accepted limits of 1.4 PO2.
Again, who are those, I am seriously intrigued being a European myself
Who are those 'Europeans'? It is such a broad concept. I was certified in the UK , lived there for 10 years, lived in the Netherlands and Germany (and some other places) for 17 years, dove all over the place. Never have I encountered 'those Europeans' who systematically dive beyond accepted limits of 1.4 PO2.
Again, who are those, I am seriously intrigued being a European myself
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