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

[texdiveguy]

"My CCR instructor requires only Nitrox certification and not advanced nitrox certification (while it's recommended, not required). The basic training that we'll be doing (Air Diluent no-deco) is no-deco diving within recreational dive limits on CCR."

Hello Howard,
What agency does your CCR Inst teaches for?
The Advanced Nitrox cert is a pre requisite for the TDI Air Diluent CCR Diver Course.
Safe Diving

IANTD.....

"Open Water Closed Circuit Rebreather Diver (OW CCR)
A. Purpose
1. This Program is designed to train competent divers in the safer use and technology of basic CCR diving with no decompression, up to 1.2 PO2 and to depths up to 70 fsw (21 msw). This course may be used as an entry-level course to SCUBA diving if combined with the OW program in which case OC dives will be substituted with CCR dives. The diver can dive to a maximum depth of 100 fsw (30 msw) if they are guided or supervised dive by a rebreather supervisor or instructor. The training requirements here in are IANTD minimums. Other manufacturerÃÔ requirements MAY APPLY for specific rebreathers so consult manufacturers literature prior to teaching.
B. Prerequisites
1. Must be either an IANTD EANx Diver or equivalent or it may be taken in conjunction with the EANx Diver class.
2. Must be a minimum of 17 years of age.
C. Program Content
1. All lectures completed with IANTD Course-specific Slides pertaining to the theory in the IANTD OW CCR-specific Diver Student Kit.
2. This program must include a confined water session, followed by 4 OW dives with a minimum of 300 minutes of in-water training time on the specific rebreather for which the diver is being trained.
2. Students must pass the specific OW CCR test with a minimum score of 80%.
3. The student and instructor must carry sufficient gas to ascend safely to the surface in the event of a bailout to OC is required and to adequately support the OC bailout practices."

 

[nereas]

I guess my problem is that I don't know if the dive can be handled with the narcosis until I am faced with an emergency and some task loading. It comes down to judgment as to which is the greater risk: Narcosis preventing me from handling an emergency properly when and if that happens, or screwing up my buoyancy with a fast gas.

I honestly don't have th experience to make that call properly, although from my arm chair I imagine that the "difficulty" of the dive might be an important consideration. If doing a wreck penetration in cold water with current, maybe you need your wits about you. Whereas if doing a nice warm wall dive, you might consider narcosis less of a threat. Not sure, just tossing ideas around.

Why wouldn't you do a complete trimix dive, preferably a dive you already know well? That way, if you finished the dive thinking you saw a ton of stuff you had missed before, you would get a better read on the benefits...

Since you started this thread, and it is your thread, I would like to address your question.

Note that some training groups avoid deep air exposure like the plague and preach concurrence with that philosophy.

Others have a phase of deep air training.

Once you have experienced air at 185 ft you will likely never try it again. It compares with a really bad drunkenness.

If you never experience it then you simply need to have faith that the best mix for any given dive is a low ppN2 equivalent to 85 or 90 ft. The price you pay in return is more deco time with a helium mix. But if your dive is worth diving, then it is worth the deco time as well.

What depth you dive to depends entirely on your target down there. If it is a shipwreck, then it sank where it sank, and to get down to it you need to be trained and certified and follow the procedures to safely do so. Whether it is at 100 ft, or 200 ft, or 300 ft.

And for anything deeper than that you would need a CCR and a good CCR buddy with you at all times watching your every move as you watch theirs.

If you are thinking of going down the CCR road, then it makes sense to make up your mind before you buy a lot of O/C tech gear. They each cost in the range of $15K US. Best not to buy both.

 

[Reg Braithwaite]

What depth you dive to depends entirely on your target down there. If it is a shipwreck, then it sank where it sank, and to get down to it you need to be trained and certified and follow the procedures to safely do so. Whether it is at 100 ft, or 200 ft, or 300 ft.

I've dived to 143' on air twice in gorgeous, sunlit, warm water (Reino Magico at Isla Juventud, Cuba) and to 135' in gorgeous, cold water on the Forest City in Tobermory, Ontario. And a few others deeper than 100', some cold, some warm.

Right now, I am not consumed with a desire to go deeper for its own sake, and up here in Ontario there is plenty to explore at shallower depths. That being said, I am quite aware I got narc'd and I am not particularly enamoured of the idea of dealing with an emergency when my judgement is impaired.

So, my goal is to become a better diver on "recreational" dives, thus my interest in some form of Intro to Tech training (like DIR-F) where there will be an emphasis on trim and bouyancy control and executing basic procedures correctly. I see learning more about gas mixes as an add-on to such training, but not an end in itself.

A Recreational Helium course could be useful for improving my dives in the depths I am already diving, thus my interest in it. Advanced Nitrox doesn't seem that useful unless you are taking it as a stepping stone to technical diving, but I will probably take it eventually. Accelerated deco on 100% O2 might be useful one day for contingencies, and someone pointed out that having a cylinder of 100% O2 is useful if you also take an O2 provider course.

 

[jtivat]

If you never experience it then you simply need to have faith that the best mix for any given dive is a low ppN2 equivalent to 85 or 90 ft. The price you pay in return is more deco time with a helium mix. But if your dive is worth diving, then it is worth the deco time as well.

Well I guess that depends on the model you are using and depth.

Dive one with air RT 79.

Decompression model: VPM - B

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

Dec to 180ft (3) Air 60ft/min descent.
Level 180ft 27:00 (30) Air 1.32 ppO2, 179ft ead
Asc to 110ft (32) Air -30ft/min ascent.
Stop at 110ft 0:40 (33) Air 0.89 ppO2, 109ft ead
Stop at 100ft 1:00 (34) Air 0.82 ppO2, 99ft ead
Stop at 90ft 2:00 (36) Air 0.76 ppO2, 89ft ead
Stop at 80ft 2:00 (38) Air 0.70 ppO2, 79ft ead
Stop at 70ft 2:00 (40) Nitrox 50 1.52 ppO2, 31ft ead
Stop at 60ft 3:00 (43) Nitrox 50 1.37 ppO2, 25ft ead
Stop at 50ft 4:00 (47) Nitrox 50 1.23 ppO2, 19ft ead
Stop at 40ft 6:00 (53) Nitrox 50 1.08 ppO2, 12ft ead
Stop at 30ft 7:00 (60) Nitrox 50 0.93 ppO2, 6ft ead
Stop at 20ft 7:00 (67) Oxygen 1.57 ppO2, 0ft ead
Stop at 10ft 12:00 (79) Oxygen 1.27 ppO2, 0ft ead
Surface (79) Oxygen -30ft/min ascent.

Off gassing starts at 132.4ft

OTU's this dive: 106
CNS Total: 43.0%

127.0 cu ft Air
25.0 cu ft Nitrox 50
13.1 cu ft Oxygen
165 cu ft TOTAL


DIVE PLAN COMPLETE

Dive 2 with mix RT 72 min.


Decompression model: VPM - B

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

Dec to 180ft (3) Triox 21/35 60ft/min descent.
Level 180ft 27:00 (30) Triox 21/35 1.32 ppO2, 85ft ead, 105ft end
Asc to 110ft (32) Triox 21/35 -30ft/min ascent.
Stop at 110ft 0:40 (33) Triox 21/35 0.89 ppO2, 46ft ead, 59ft end
Stop at 100ft 1:00 (34) Triox 21/35 0.82 ppO2, 40ft ead, 53ft end
Stop at 90ft 1:00 (35) Triox 21/35 0.76 ppO2, 35ft ead, 46ft end
Stop at 80ft 2:00 (37) Triox 21/35 0.70 ppO2, 29ft ead, 40ft end
Stop at 70ft 2:00 (39) Nitrox 50 1.52 ppO2, 31ft ead
Stop at 60ft 2:00 (41) Nitrox 50 1.37 ppO2, 25ft ead
Stop at 50ft 2:00 (43) Nitrox 50 1.23 ppO2, 19ft ead
Stop at 40ft 4:00 (47) Nitrox 50 1.08 ppO2, 12ft ead
Stop at 30ft 6:00 (53) Nitrox 50 0.93 ppO2, 6ft ead
Stop at 20ft 7:00 (60) Oxygen 1.57 ppO2, 0ft ead
Stop at 10ft 12:00 (72) Oxygen 1.27 ppO2, 0ft ead
Surface (72) Oxygen -30ft/min ascent.

Off gassing starts at 130.8ft

OTU's this dive: 98
CNS Total: 40.1%

125.2 cu ft Triox 21/35
18.0 cu ft Nitrox 50
13.1 cu ft Oxygen
156.3 cu ft TOTAL


DIVE PLAN COMPLETE

 

[battles2a5]

Once again nereas, you have proven that you know abo****ely nothing about technical diving. You really should not be giving advice on a topic you know nothing about, especially to someone that is actually interested in doing the dives.

If you never experience it then you simply need to have faith that the best mix for any given dive is a low ppN2 equivalent to 85 or 90 ft. The price you pay in return is more deco time with a helium mix. But if your dive is worth diving, then it is worth the deco time as well.

Helium vs. deep air is NOT an argument about narcotic load vs. deco time. It is about MANAGING narcotic load and CNS. The deco is a secondary concern. Bus since helium is easier to decompress from and depending on the algo you use, you will likely find shorter deco times on mix vs. air on any dive worth using He.

And for anything deeper than that you would need a CCR and a good CCR buddy with you at all times watching your every move as you watch theirs.

First of all, you can dive OC beyond 300ft. Second of all, if you are diving beyond 300 on a CCR or OC for that matter, you shouldn't need anybody to watch your every move. Buddies are great to have, but self-sufficiency at this level is paramount.

If you are thinking of going down the CCR road, then it makes sense to make up your mind before you buy a lot of O/C tech gear. They each cost in the range of $15K US. Best not to buy both.

There are very few CCRs that cost 15k. And any OC gear and training you accumulate on the way to CCR is not wasted. If you are diving deep on CCR, you still need to know how to bail out onto OC and get yourself out of the dive.

 

[ppo2_diver]

I've read many people talking about narcosis in this thread, but what about CO2? I believe this is the biggest concern in deeper diving (other than Ox Tox). While CO2 may be the leading cause of narcosis, it also leads to blackout, which isn't manageable. When adding He, you can reduce the CO2 being produced. Thus reducing the risk of blacking out and narcosis of course.

Just my 2 psi.

 

[texdiveguy]

I've read many people talking about narcosis in this thread, but what about CO2? I believe this is the biggest concern in deeper diving (other than Ox Tox). While CO2 may be the leading cause of narcosis, it also leads to blackout, which isn't manageable. When adding He, you can reduce the CO2 being produced. Thus reducing the risk of blacking out and narcosis of course.

Just my 2 psi.

You should start another thread on deep diving/CO2, as few divers other than those that apply the study know little about this 'black gas'.

 

[Reg Braithwaite]

I've read many people talking about narcosis in this thread, but what about CO2? I believe this is the biggest concern in deeper diving (other than Ox Tox). While CO2 may be the leading cause of narcosis, it also leads to blackout, which isn't manageable. When adding He, you can reduce the CO2 being produced. Thus reducing the risk of blacking out and narcosis of course.

Well, I hate to actually discuss the original question, but out of respect to the OP...

Originally, the question was which course would be more useful: Advanced Nitrox or Recreational Trimix? Which led inexorably to what kinds of mixes would be practical and affordable in the depths and durations I plan to dive.

I honestly don't know: is CO2 a problem for short dives in the 100' to 140' range? I imagine "recreational trimix" being interesting for a dive like the Forest City: it lies on a slope with the bow at about 70' to 150' if you visit the rudder under the stern.

The railing is about 135', you can visit it, shine your light on the rudder, then make your way up to the bow slowly, visiting the boilers on the way. You'll probably pass a couple of thermoclines on the way down and back up, you you have a few incentives for not spending too much time at the stern.

I realize that the "bottom time" of a no deco dive is quite short, but you still spend significant time deeper than 80', so I'm quite interested in lowering the END on a dive like this.

Is lowering CO2 a significant factor for a dive like this? I honestly don't know. It certainly can't hurt. That being said, I imagine that the first order of business for being a safe deep diver is breathing correctly, and only then working on the gas mixture.

 

[ianr33]

.
I honestly don't know: is CO2 a problem for short dives in the 100' to 140' range?

Is lowering CO2 a significant factor for a dive like this? I honestly don't know. It certainly can't hurt.

I dont see CO2 being a problem provided you are relaxed and breathing steadily and deeply. BUT if you are working your butt off fighting a current at 140 feet with a crappy rental reg then start hyperventilating it could easily become a big problem.

As to Advanced Nitrox/Recreational Trimix I would go with the Advanced Nitrox. It opens up a whole new world of long and deep(ish) dives. Recreational Trimix just lets you do a deep(er) bounce. Doing NDL dives deeper than ,say,130 is kind of pointless IMHO.

 

[HowardE]

Helium reduces CO2 production? CO2 "retention" is from shallow breathing (or failure to fully expire, and rebreathe your exhaled breath from dead spaces within your regulator's second stage), and failure to fully expire the CO2 produced from your breath. Deeper dives require more force to fully expire your breath, and can result in increased CO2 levels. How does Helium offset this?

Back to the OP's original question... I also find that a "recreational trimix" (or Helitrox) course which limits the divers to the recreational dive limits (130 Feet) is fairly pointless. It's not a tech course from what I understand about the class (I know someone who is taking it now) and they aren't doing staged decompression. Helium will force the divers to monitor their ascent rate, and change their END from 130' to 90' ?? I don't see the value.

Advanced Nitrox is a building block for decompression diving, and has value.