PADI Enriched Air Certification.... a little fishy.

[billgraham]

If you are diving a mix you can't safely dive at 15 feet deeper than the plan, you are probably on the wrong mix anyway.

And on top of that, the risk of diving at something like 1.45 instead of 1.4 is probably really not worth worrying about all that much. If I am remembering right, it wasn't too long ago that 1.6 was considered appropriate for the working part of the dive and I've heard in the past numbers as high as 2.0 were used.

Oh sure, AWD did all those Andrea Doria dives on air back in the day (PPO2 = 1.7), but you don't see any of those guys doing it now, do you? I am aware of a tox incident that happened at a PPO2 of 1.4, so it's better to understand it, and it doesn't take much to teach/learn it.

So now you're changing your hypothetical situation. If you know it will be between 90-130fsw... why would you bring 34% with you?

On our boat we will typically tell you a specific wreck. If we change destinations - which is not uncommon - it will be same depth or shallower. Sometimes we will specify a depth, and choose the wreck at the dock or the way out based on conditions and passenger desire. We would never go deeper than planned*. Don't know of a boat that would. Would never dive with one that did. This is a "dive op" problem, not a "dive planning" problem.

*Unless everyone on board had appropriate gas and desire.

I've changed the hypothetical a number of times here. Why would you bring 34% with you? Because you had it left over from the week before when you got blown out, and took a %$#& nitrox course? If I'm not mistaken, this particular boat has been running longer than any other in the Northeast and everyone knows their protocol. If I were diving open circuit, I'd have 28% and o-2 so it wouldn't matter where we went. I dive on lots of different boats, each has their own way of doing things. I'm just trying to come up with illustrations of why it's smart to actually learn Dalton's diamond. I strongly disagree with all dive training being tailored to the least common denominator.

 

[RJP]

Why would you bring 34% with you? Because you had it left over from the week before when you got blown out, and took a %$#& nitrox course?

So you would bring the wrong gas for the planned dive in your example (up to 130ft) simply because you had it left over? That's just stupid, irrespective of whether or not you know Dalton's Diamond.

Believe me, I'm with you on the desirability of knowing how to calculate MOD, best mix, etc. You're just not helping your case with examples that effectively have nothing to do with that ability

 

[rhwestfall]

re-stating again, the OceanX calculator in the NAUI materials is a wonderful tool....

 

[billgraham]

So you would bring the wrong gas for the planned dive in your example (up to 130ft) simply because you had it left over? That's just stupid, irrespective of whether or not you know Dalton's Diamond.

Believe me, I'm with you on the desirability of knowing how to calculate MOD, best mix, etc. You're just not helping your case with examples that effectively have nothing to do with that ability

Of course not, I would have 28% and O-2, as I said. I have definitely seen people show up with the wrong mix and not get on the boat over the years. Think of a better example and post it, I've come up with four or five here. I said it earlier: fine, don't teach it, don't bother learning it, just don't expect the divers who take those courses to be able to make informed decisions above or below the water.

 

[hypertech]

I'd rather have someone write the MOD down on a sticker from a table and put it on the tank than screw up the math in their head on a rocking boat.

 

[billgraham]

Hyper, of course, but MOD is just that, it's calculated at a PPO2 of 1.6.

 

[RJP]

Think of a better example and post it, I've come up with four or five here.

I have no need/desire to support your position.

PS - You're arguing against a position that no one else is taking. I'm just saying that your examples don't support your point. If someone shows up at the boat with the wrong mix because the destination was changed it doesn't whether they used a table, Dalton's Diamond, or an abacus to calculate their mix -- it's the wrong mix, and how they calculated their mix doesn't matter. The guy who knows his math inside and out is going to be left at the dock just the same as the guy who relied on a nitrox table.

 

[hypertech]

Hyper, of course, but MOD is just that, it's calculated at a PPO2 of 1.6.

Is it? I can calculate a MOD at any PPO2. Or, I can look at the chart at the fill station after I analyze my tank and just write it down from the 1.4 or 1.6 column for whatever mix I actually ended up with in the tank.

 

[mala]

I'd rather have someone write the MOD down on a sticker from a table and put it on the tank than screw up the math in their head on a rocking boat.

30% nitrox.

surface pp02 is .3
at 10 m .6
20m .9
30m 1.2
40 m 1.5
50m 1.8

i think the boat would need to rock quite a lot not to be able to do the maths.

 

[weitodive]

Hyper, of course, but MOD is just that, it's calculated at a PPO2 of 1.6.

By PADI course materials mod is 1.4. Contingency is 1.6.