What's the deal with the "Advanced Nitrox" certification?

[nereas]

If you check some of Nereas' posts you will see he often advocates a pO2 of 1.6 on the bottom section of a dive.

He can do whatever he wants but I wish he would not advise new(er) divers to do this.No agency will teach it.

It depends on your entire dive plan. There is nothing voodoo about 1.6 ppO2.

Depending on your entire dive plan, the ppO2 needs to be set normally somewhere between 1.2 and 1.6 ppO2.

We have beaten this to death in other threads.

 

[nereas]

please do the math on that. 30/30 would give you a PPO2 of almost 1.6 at 140'. it's recommended to keep the MOD at 100' for 30/30. That's why some like 25/25 as it allows for a MOD of 130'.

yeah, we clearly don't know what depths our gases should be used and can't explain why.

The math is fine.

But don't confuse yourself either. I do not advocate TMX 30/30 other than as a deco mix.

 

[ianr33]

Depending on your entire dive plan, the ppO2 needs to be set normally somewhere between 1.2 and 1.6 ppO2.

Have you ever been taught that in a class? (Talking bottom gas only here)

 

[Reg Braithwaite]

If IANTD sells 28/25 as covering 30/30, then I must conclude (contrary to what I was taught... by IANTD) that the tolerance on oxygen is +/-2%, and thus those two gases can be identical (30/20).

I'd love to get a hold of those tables and see how much the deco varies.

(Note, I am not advocating diving any table other than the exact one for which your analyzed mix calls for).

I am NOT advocating their approach, just reporting my understanding. But if you are interested...

IANTD Charts & Tables Scuba Rebreather IANTD nitrox ean eanx trimix

Recreational Trimix 28/25 w/ 50% Deco - 28/25% Trimix NDL & Deco
w/Optional 50% Accelerated Deco. This table is for 28/25% Trimix (28% Oxygen with 25% Helium or greater) as both bottom gas and as the deco gas. They also offer an optional accelerated deco schedule (highlighted in green) using 50% up to 80% Nitrox at the last three stop depths. This is the table to use with 30/30% Trimix.

I can't see myself blindly buying a table and following it regardless of what is in a course and who teaches it. This is where mentoring is helpful: I get to ask what an experienced diver uses to calculate their dive profile and how.

 

[Blackwood]

But if you are interested...

IANTD Charts & Tables Scuba Rebreather IANTD nitrox ean eanx trimix

I am interested, though not enough to buy tables I'll never use

I can't see myself blindly buying a table and following it regardless of what is in a course and who teaches it.

:thumbs-up

 

[ianr33]

Does anybody in the real world actually use tables like these?

Seems kind of pointless when V-planner,decoplanner etc. exist and work so well.

 

[Reg Braithwaite]

Does anybody in the real world actually use tables like these?

Seems kind of pointless when V-planner,decoplanner etc. exist and work so well.

It is tough to figure out the market for tables when you can cut your own using vPlanner/iDeco/whatever, or use a dive computer, or buy into a standard gas + figure it out in your head methodology. (I am not saying any of these are appropriate, just agreeing that it's hard to envisage a "market" for pre-printed tables like this).

That seems especially true for NDL dives.

 

[texdiveguy]

When I got into trimix diving years back I bought a select few of the IANTD Trimix Tables that were in the area of the dive profiles I was doing simply to keep in my log book binder......have referred to them in the field several times..... like most folks I use a computer program/Deco Planner 3.0 for cutting tables.

 

[jtivat]

Run your same comparison using TMX 30/30 versus EAN 30. That would be more relevant.

Why would you say something like this without checking to make sure you know what you are talking about first??? Again the Helium dive is shorter!


Dive one with Air RT 46 min.


Decompression model: VPM - B

DIVE PLAN
Surface interval = 5 day 0 hr 0 min.
Elevation = 570ft (c)
Conservatism = + 3

Dec to 130ft (2) Nitrox 30 60ft/min descent.
Level 130ft 27:50 (30) Nitrox 30 1.44 ppO2, 111ft ead
Asc to 70ft (32) Nitrox 30 -30ft/min ascent.
Asc to 40ft (33) Nitrox 50 -30ft/min ascent.
Stop at 40ft 1:00 (34) Nitrox 50 1.08 ppO2, 12ft ead
Stop at 30ft 3:00 (37) Nitrox 50 0.93 ppO2, 6ft ead
Stop at 20ft 3:00 (40) Oxygen 1.57 ppO2, 0ft ead
Stop at 10ft 6:00 (46) Oxygen 1.27 ppO2, 0ft ead
Surface (46) Oxygen -30ft/min ascent.

Off gassing starts at 79.3ft

Dive two with mix RT 43.


Decompression model: VPM - B

DIVE PLAN
Surface interval = 5 day 0 hr 0 min.
Elevation = 570ft (c)
Conservatism = + 3

Dec to 130ft (2) Triox 30/30 60ft/min descent.
Level 130ft 27:50 (30) Triox 30/30 1.44 ppO2, 49ft ead, 80ft end
Asc to 70ft (32) Triox 30/30 -30ft/min ascent.
Asc to 40ft (33) Nitrox 50 -30ft/min ascent.
Stop at 30ft 2:00 (35) Nitrox 50 0.93 ppO2, 6ft ead
Stop at 20ft 3:00 (38) Oxygen 1.57 ppO2, 0ft ead
Stop at 10ft 5:00 (43) Oxygen 1.27 ppO2, 0ft ead
Surface (43) Oxygen -30ft/min ascent.

Off gassing starts at 77.3ft

OTU's this dive: 68
CNS Total: 28.8%

88.9 cu ft Triox 30/30
3.7 cu ft Nitrox 50
5.5 cu ft Oxygen
98.1 cu ft TOTAL


DIVE PLAN COMPLETE

OTU's this dive: 72
CNS Total: 30.0%

88.9 cu ft Nitrox 30
6.0 cu ft Nitrox 50
6.1 cu ft Oxygen
100.9 cu ft TOTAL


DIVE PLAN COMPLETE

 

[nereas]

Why would you say something like this without checking to make sure you know what you are talking about first??? Again the Helium dive is shorter!


Dive one with Air RT 46 min.


Decompression model: VPM - B

DIVE PLAN
Surface interval = 5 day 0 hr 0 min.
Elevation = 570ft (c)
Conservatism = + 3

Dec to 130ft (2) Nitrox 30 60ft/min descent.
Level 130ft 27:50 (30) Nitrox 30 1.44 ppO2, 111ft ead
Asc to 70ft (32) Nitrox 30 -30ft/min ascent.
Asc to 40ft (33) Nitrox 50 -30ft/min ascent.
Stop at 40ft 1:00 (34) Nitrox 50 1.08 ppO2, 12ft ead
Stop at 30ft 3:00 (37) Nitrox 50 0.93 ppO2, 6ft ead
Stop at 20ft 3:00 (40) Oxygen 1.57 ppO2, 0ft ead
Stop at 10ft 6:00 (46) Oxygen 1.27 ppO2, 0ft ead
Surface (46) Oxygen -30ft/min ascent.

Off gassing starts at 79.3ft

Dive two with mix RT 43.


Decompression model: VPM - B

DIVE PLAN
Surface interval = 5 day 0 hr 0 min.
Elevation = 570ft (c)
Conservatism = + 3

Dec to 130ft (2) Triox 30/30 60ft/min descent.
Level 130ft 27:50 (30) Triox 30/30 1.44 ppO2, 49ft ead, 80ft end
Asc to 70ft (32) Triox 30/30 -30ft/min ascent.
Asc to 40ft (33) Nitrox 50 -30ft/min ascent.
Stop at 30ft 2:00 (35) Nitrox 50 0.93 ppO2, 6ft ead
Stop at 20ft 3:00 (38) Oxygen 1.57 ppO2, 0ft ead
Stop at 10ft 5:00 (43) Oxygen 1.27 ppO2, 0ft ead
Surface (43) Oxygen -30ft/min ascent.

Off gassing starts at 77.3ft

OTU's this dive: 68
CNS Total: 28.8%

88.9 cu ft Triox 30/30
3.7 cu ft Nitrox 50
5.5 cu ft Oxygen
98.1 cu ft TOTAL


DIVE PLAN COMPLETE

OTU's this dive: 72
CNS Total: 30.0%

88.9 cu ft Nitrox 30
6.0 cu ft Nitrox 50
6.1 cu ft Oxygen
100.9 cu ft TOTAL


DIVE PLAN COMPLETE

You and I seem to be miscommunicating.

Run V-planner for TMX 30/30 and NO DECO GASSES, and compare it with EAN 30 AND NO DECO GASSES.

Then let's see what you get.