Do I need Nitrox?

[UB]

used 11 liter tank for the dive air consumption is the main concerned.
You must know the water condition/movement

Two different dive table
PADI Dive Table 10m - 42m
PADI Dive table is from 10m 120 minute go 122 minute Group T - 60 minute SIT Group G 10m ADT178 minute RNT41
PADI Dive Table 12m Minute go 125 minutes Group X 60 minutes SIT Group I ADT 105 minute RNT 42
NAUI Dive table 12m - 42m
NAUI Dive Table 12m 120 minute go 130 minute Group K 60 minute SIT Group I AMDT 29 RNT 101

NAUI Dive Table 12m 120 minute go 130 minute Group K 60 minute SIT Group I AMDT 29 RNT 101

This is what I was concerned about and why I was considering nitrox. If I remember my training from NAUI correctly - any dive less than 40ft (12m) I should use the 40ft (12m) table. So according to NAUI (and based on what Jason posted above) - at the completion of my first dive I would be a Group K (rounding my 120min dive to 130min per NAUI recommendation). With a 1 hr SIT I would be an "I" for my next dive to 25ft (12m) which would have given me an Adj Max Dive Time of 29 minutes (I actually did 120 min).

NAUI Air Tables - http://orgs.bloomu.edu/scuba/divetables/divetables.html

If I review the Nitrox tables for the same dive profile I would not have exceeded my limit on my second dive

FYI - I was using my computer which indicated I did not have a problem.

Reasons for me going to Nitrox:
1 - It "appeared" I would be safer on Nitrox (based on the NAUI) table, but now I am not sure, if I understand some comments there may be an issue with Nitrox at shallow depths?.
2 - The difference between Nitrox and Air rentals or refills is ~$2 (nothing I couldn't afford).
3 - I would like to further increase my down time (I was never in a hurry to end a dive). One way I could do this is by jumping up from 80s to 100s which I can only locally rent in Nitrox.

Thanks

 

[rongoodman]

I found that the TDI Nitrox course gave me a lot of practice working with partial pressures, computing EADs, working with the dive tables. I'd seen it before, but taking the course made me more comfortable with it.

 

[rottielover]

I tend to agree with RTW here (also as a freshly cert.'d Nitrox diver)...

While "should I use nitrox?" has been answered over and over with, 'you don't NEED too". I fail to see how nitrox would be more dangerous than air on this dive profile.

Again, I don't have my tables here at the office, but I find it hard to belive that he would violate a 1.4 PP on this profile with a mix less than 40%.

Taken further, if you use the AIR tables to plan your dives (always keeping in mind your O2 exposure) then there is the added benifit of LESS nitrogen in the system.

I just don't understand what your getting at Olympic... No one should be using Nitrox unless certified for it anyway, meaning that anyone using nitrox should be trained to understand the complications.

I still think the answer on this thread would have to be:

"No, you do not NEED to use nitrox on this dive, in fact many of your fellow divers would simply use AIR to save some money for other things. However, if your interested in Nitrox, check out the classes and see if you can find a good instructor".

2 bubble's worth

 

[PerroneFord]

Ok,

The recreational tables are an incredibly crude tool. It's like trying to measure ants with a yardstick. Your computer on your wrist is a far more accurate tool with which to measure your dive, and it is based on the same formula as the tables, but is measuring the depths correctly, which the tables cannot do.

There is no "danger" in using nitrox for these dives, it's just that the benefits of Nitrox are not really realized with the shallow depths you are diving. Nitrox really shines between 50 and 80ft, when compared to air. Below that, other gases start to look better, and shallower, there just isn't much call for it. That said, I dive Nitrox on all my dives, even one's shallower than you mentioned here. The cost to me is negligible.

If you used recreational levels of nitrox, you could quite easily extend your dive time to 4, 6, or more hours. If that is what you want.

Reasons for me going to Nitrox:
1 - It "appeared" I would be safer on Nitrox (based on the NAUI) table, but now I am not sure, if I understand some comments there may be an issue with Nitrox at shallow depths?.
2 - The difference between Nitrox and Air rentals or refills is ~$2 (nothing I couldn't afford).
3 - I would like to further increase my down time (I was never in a hurry to end a dive). One way I could do this is by jumping up from 80s to 100s which I can only locally rent in Nitrox.

Thanks

 

[UB]

Your computer on your wrist is a far more accurate tool with which to measure your dive, and it is based on the same formula as the tables, but is measuring the depths correctly, which the tables cannot do.

That is an excellent point. My concern was that maybe the computer's algorithm is incorrect at these depths - but I think you are right in that it is probably more accurate than using the conservative assumptions in the tables.

 

[RJTY]

I could be wrong, but I seem to remember in the NAUI OW workbook, the question asked if while using a computer, do you defer to your tables or computer. I believe the answer was computer.

 

[PerroneFord]

If you look at your tables, try to see the difference in spending an hour at 40ft, versus 50ft. You are talking about rounding 15-20ft with the tables. HUGE discrepancy.

 

[olympic divers]

I agree with most of what is being posted here. He won't get hurt using Nitrox at these depths but he should stick to what he has been trained in and not experiment with something new on his own without instruction. Computers are great but when they wrong, you don't know by how much. Sticking to tables is safe, conservative, and a good practice.

 

[PerroneFord]

Sticking to tables is safe, conservative, and a good practice.

My tables say I can dive to 130ft on air, stay 10 minutes, come up directly to 15ft at 60fpm, stop for 3 minutes, and get out of the water.

Is that safe, conservative, and good practice?

Tables are a crude tool that do an ok job. The world has moved on, and there are better and safer methods of diving out there.

 

[olympic divers]

I know what you're saying. I'd use USN ascent rate of 30. In my original post I was just trying to communicate to the guy that there are unknowns that he probably hadn't considered and to stick with what he knows until he gets a better understanding. His question was Do I need Nitrox? And the simple answer to that is no.