DIR variances

[rjack321]

The official take on this is that we will allow the different variances taught by the Heretic (AG ) and other DIR-like instructors.

The reality is that there would be differences between what was taught between two GUE diver from different "eras", so why worry about it.

Most of the differences I have seen have been trivial anyways.

Plus, it will give us something to debate about.

debating valve drills or 25/25 vs. 30/30 is ALOT better than than MOF vs. NMOF lol

 

[amascuba]

debating valve drills or 25/25 vs. 30/30 is ALOT better than than MOF vs. NMOF lol

You're going to die if you dive 25/25, while reaching for your isolator first while doing a valve drill, and with your mask on your forehead ....all at the same time.

On a more serious question though. Why does AG teach 25/25 over 30/30? The only reason that I can think of is that it's easier to mix if you bank EAN32, which also follows the same procedures for mixing 21/35, 18/45, 15/55, and 10/70 with banked EAN32. Is their any advantage over using it during the dive?

 

[rjack321]

In bullets (not my arguments)

30/30 has "too high" a ppO2 to use throughout its depth range (80-120)
30/30 recently revised depth limits to 80-100 - what's the point of that when you could use 32%?

25/25 has minimal deco penalty
easy to mix
allows a wider depth range at ppO2 of 1.2



Personally I can use either, here's my selection criteria:
0' - 100' : Nitrox 32
80 - 110 : Triox 30/30
90 - 120 : Triox 25/25
121 - 150: 21/35
151 - 200: 18/45

In the 80 - 120ft range gas choice needs to be a team decision based on the objectives of the dive. I.e. I would not use 32% at 100ft inside a wreck. Nor would I use 25/25 at 90ft in OW. I might use 30/30 at 90ft in OW if there were significant currents or other site hazards requiring me to be at the top of my game. I would neither push my ppO2s to 1.4 nor disregard the extra -10% EAD benefits of 30/30 over 25/25. Gas choice should not be an "all or nothing" proposition just for the sake of standardization. Admirable as that may be, its only one aspect of planning the dive. That's my DIR answer