First Time Nitrox

[tbone1004]

Wasn't the complete quote "...at a rolling donut"?

Well I agree about safety rounding so that is the direction I am taking.

I believe it was "why don't you take a flying..." but yes, gotta love Slapstick, good book

 

[Joneill]

and in rec they should still be teaching to round to safety. To me that's their same cop out make it easier not safer bullsh!t as when they teach you to use your drysuit for primary buoyancy control. It's not safer, it's just easier. Telling you to always round the nitrox percentage up is not safer, it's easier. No tech computer I know of allows you to put fractions of a percentage in either *rebreathers aside obviously since they're measuring*, but you should still round to safety. That means manually calculating MOD, and using a different value to enter into the computer for decompression calculation, not taking the "easy" way out by rounding everything in the same direction which is more dangerous, made especially risky with how liberal PADI's dive tables are

Most rec divers determine their MOD by what their computer tells them it is after they enter their gas mix. As you really should not be pushing to an NDL of "0" as a rec diver, I think ensuring you know your true MOD is more important than knowing exact NDL (1% won't affect NDL much at rec depths - 32% vs 36% is only a 5 minute difference at 30 m according to the tables).

 

[BullDiver]

I actually paid very good attention during my nitrox class because I care about my own safety. I merely asked the DM because she was standing right there and this was my first time diving nitrox. "Safety" rounding was not presented in the Nitrox class but I understand the concept and will incorporate this into future dives. Thank you for your responses.

As for feeling better afterwards I think this may have been true. I had to drive 2 hours in the dark afterwards which tires me out anyway so no good way to tell its effects just yet.

 

[DavidFL]

I'm sure these things get revised from time to time, but my PADI Enriched Air Diving Specialty Series Imperial Edition Diver Manual (1995-2005), p.42 says essentially what the OPs DM said: "For example, if your analysis finds a blend has 31.2% oxygen, use 31% on the table or set 31% on your computer. If your analysis finds 31.8%, use 32%. You can round 31.5% either way; most people would round up to 32%"

FWIW, I agree with "round to safety".

 

[scubadada]

What a contentious thread. New divers are often gas limited, doesn't mean they should not dive nitrox for the safety advantage and they will improve their gas consumption with experience. An analyzed 33.5 is 33% for me. You could round up for MOD. That gives me 67 min at 70 ft, I might just be able to do that with an AL80. I will not come close to PO2 or oxygen limit.

 

[DogDiver]

Forget the whole round up, round down and just set your computer to 33% and just dive.

 

[scubadada]

Forget the whole round up, round down and just set your computer to 33% and just dive.

It's a perfectly good thing to be aware of the concepts involved. NDL will be most commonly limiting, but O2 exposure should not be forgotten or dismissed.

 

[Steve_C]

Personally for planning purposes I added another row to my SDI/TDI tables. I base my MOD on 1.3 and not 1.4 and even then stay away from it on most dives. But then I ride my NDL with a somewhat conservative computer even with Nitrox on dives past 60 ft.

 

[barth]

1:
For me it's easy, I never use air, only ean32.

2:
I don't use a dive computer. If oxygen is between 30,0 and 35,0 I will use a table of ean32. The mod is 100 feet/30m.

If it is less than 30,0 oxygen or more than 35,0 oxygen it depends on the dive plan. I would consider analyzing and using another tank or fill and analyze again.

 

[Centrals]

My Uwatec Aladin Pro Nitrox would only allow 2% increment from 22% onward! So it has to be either 32% or 34% in this case.
If it is 33.5% I would set my computer to 34%.

O2 tox vs ndl you have to decide which is more critical.