What is the 130 rule?
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ADeadlierSnake
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Kevrumbo
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Basically an applied instance of the old 120/20% Rule:
http://www.scubaboard.com/forums/basic-scuba-discussions/36031-dir-computers-3.html#post381802
For Repetitive Dives:
1.5 hour SIT minimum, then use 110 rule for Dive#2;
1.5 hour SIT minimum, then use 100 rule for Dive#3;
1.5 hour SIT, use 90 rule for Dive#4
1.5 hour SIT, use 80 rule for Dive#5
and so on. . .
(For more conservatism use 2hr SIT instead)
http://www.scubaboard.com/forums/basic-scuba-discussions/36031-dir-computers-3.html#post381802
For Repetitive Dives:
1.5 hour SIT minimum, then use 110 rule for Dive#2;
1.5 hour SIT minimum, then use 100 rule for Dive#3;
1.5 hour SIT, use 90 rule for Dive#4
1.5 hour SIT, use 80 rule for Dive#5
and so on. . .
(For more conservatism use 2hr SIT instead)
The other rule of 130 is that whenever a thread on scubaboard reaches 130 posts, everything constructive that can be said has been already, and the rest is just repetition or flaming
Some might say 130 is a bit 'sporty' in that case too
Some might say 130 is a bit 'sporty' in that case too
I just made it in with only 105 to spare.
DuboisP
Contributor
I prefer to calculate my ndl's for every dive with the nitrox tables, as well as programming my computer appropriate to the mix being used. This is better for me (and frankly, everyone) than using a "rule of thumb" which, by the way mathauck0814 stated accurately.
DivemasterDennis
DivemasterDennis
I've never heard of a "130ft rule" in realation ot Nitrox, nor a 40m rule for that matter (130ft = approx. 40m; 1m= 3.3ft)
What does scome to mind is that we were taught to limit the partial pressure (<= "pp") of Oxygen (<= "O2") to 1.4. Even in trimix training we were taught to limit O2 pp to 1.4 at all depths below 21m - the likely consequences of an O2 hit at depth are just too severe.
Don't wish to debate higher O2 pps just now. The question was about a 130ft rule:
It occurred to me that most people seem to buy their Nitrox mixes and the lightest mix available for sale seems to be EAN28. This would give a max depth of about 130ft when using the 1.4 max pp of O2.
1.4 max ppO2 / 5 bar total pressure = .28 % O2
With this explanation the officer meant that Nitrox is for max depth 130 ft.
He's assuming the lightest O2 % available is 28% and that max acceptable ppO2 is 1.4. Or whoever taught him the rule was making these assumptions.
What does scome to mind is that we were taught to limit the partial pressure (<= "pp") of Oxygen (<= "O2") to 1.4. Even in trimix training we were taught to limit O2 pp to 1.4 at all depths below 21m - the likely consequences of an O2 hit at depth are just too severe.
Don't wish to debate higher O2 pps just now. The question was about a 130ft rule:
It occurred to me that most people seem to buy their Nitrox mixes and the lightest mix available for sale seems to be EAN28. This would give a max depth of about 130ft when using the 1.4 max pp of O2.
1.4 max ppO2 / 5 bar total pressure = .28 % O2
With this explanation the officer meant that Nitrox is for max depth 130 ft.
He's assuming the lightest O2 % available is 28% and that max acceptable ppO2 is 1.4. Or whoever taught him the rule was making these assumptions.
That's an interesting bit of reverse engineering.
Since the recreational diving limit is considered to be 130', most dive shops would have no reason to go any lower than 28% Nitrox for recreational diving. In that sense, the logic is circular and the 130 rule does not relate to the limit of available nitrox but rather to the recreational limit itself (that in turn would dictate 28%).
By that same logical process and given that 32% is far more common, I'd expect to hear about the 110 rule, not the 130 rule. And in any event tech oriented shops will sell 25% nitrox to reflect the 150' Advanced Nitrox and Deco Procedures depth limit, yet we don't have a 150 rule.
I'll stand on the previous interpretation that the 130 rule works well with Nitrox 32 (referred to by NOAA as Nitrox I) under the original NOAA NDLs at depths from 70-100 feet.
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