Nitrox table vs computer question

[Lizard Leg]

Trying to decide if I want to do the Nitrox class before we head to Florida at the end of this month.

Had a question. Tables vs. Computer. We both dive Suunto Zoop's. Tables and math, I come up with:

Planned max depth - 120fsw
planned target PPO2 - 1.4
EAN32 mix

MOD for 1.4 at 32% is 111.38fsw, at 120fsw my PPO2 goes to 1.48. At 120fsw EAD is 98.70 and NDL on air is 13 minutes, 20 minutes on Nitrox.

All of this is the straight forward math and tables. All numbers are rounded so might be slightly different than you get, so please no flames.

My question - diving a nitrox capable computer, anyone have best guess ideas as to what kind of real world numbers can I expect for NDL computer vs. tables, all things being equal?

 

[Them]

In planning mode my nitrox computer and my NAUI (because that's what I have) nitrox tables come out about the same for a given mix. That is of course all square profile.

I don't have real-world numbers for you but I suspect it's just like air...the computer benefit is credit for time not at depth.

PPO is based on fraction and absolute pressure. MOD is based on a safe threshold PPO. Computer or tables, that physics doesn't change. If you want a 1.4 limit you are going to be about 111FSW for a 32 mix. The time it gives you will vary depending on not only the model the computer uses, but how conservative the computer is set to be (for computers where that's adjustable).

 

[rhwestfall]

Take the class.....

Do you have a Nitrox capable computer? Does it have a "pre-dive" planning mode? Can you set your gas to you mix, and get the NDLs for various depths? Your specific answere can be gotten there.

I still believe the class is good for further understanding.... please take it.

The planning tool that is available through DiveNav is also helpfull....

 

[DevonDiver]

Assuming square profile, the NDL will be dictated by the relative algorithm used by your computer.

Assuming multi-level profile, we'd need more specifics to give an answer

If you Google image search, you can find copies of various agencies Nitrox tables for inspection..

 

[Tyger]

I can't give a specific answer to your question as I just did nitrox recently, and PADI doesn't teach tables anymore... (Though I did learn them, just had to go find them myself.)

However with the zoop, when calculating MOD it has an annoying feature where it adds 1% to the mix you enter. So it reports the MOD at 1.4 PPO2 of EANx32 as 107fsw. This was rather annoyingly confusing until I read the manual and it said it does exactly that.

I still believe the class is good for further understanding.... please take it.

Not to mention it is good for getting nitrox fills, when they ask for your C card.

 

[Them]

Personally, based on the question LL is asking, I'm not sure the class would really help him understand the subject any better. At least not the class I took. I made the mistake of researching the subject and reading the book before class and the only value of the class was a chance to use an O2 analyzer on a tank of EAN36.

Plus the card I guess.

 

[Lizard Leg]

I've researched the math side of it and will take the course, just trying to decide if I want to try to squeeze into this months hectic schedule.

I haven't had a chance to do a dive plan on the Zoop yet, and the DivePal program doesn't let me put in a mix - and when I try to upgrade to the full version to do so, I get a 404.

On another note, the dive plan is max depth 120fsw, with the majority of the dive at 100-10fsw or so. In planning with tables, because max depth is 120, my PPO2 is over the 1.4 recommended - so how does that work IRL?

 

[DevonDiver]

I've researched the math side of it and will take the course, just trying to decide if I want to try to squeeze into this months hectic schedule.

It may not be your preference, but just so you are aware... you can do all the theory elements of the PADI Nitrox course (i.e. 99% of the course) via online learning now.

 

[Lizard Leg]

DevonDiver, that's what we plan on doing - easier for us that way!

 

[Akimbo]

In practice, it can be huge. It is rare that recreational divers follow a square profile — spend all their time at the deepest depth as tables assume. The advantage of an air or Nitrox computer is you get credit for the time spent shallower. This can be enormous on a wall or even a tall wreck since you can hit your deepest depth and explore your way to shallower water getting a far longer no-D dive out of the deal.

The advantage provided by the Nitrox tables over air tables is roughly proportional on a meandering dive profile. You also start to see compounding advantages on repeds, a really big deal on liveaboard$.

IMHO, get your Nitrox card even if you don’t use it. It will give you the understanding of physics and physiology that any diver should have, but the merit-badge dive classes don’t provide anymore.