Is there any reason to do a Nitrox 'course'?

[Wookie]

Cost is a factor. Other then empirical evidence of "feeling better" or what seems common sense that you are "adding conservatism" has there ever been a case study that concluded it was in fact safer? IOW a lower incidence of DCS?

My training said the answer was no. Is that no longer true?

Sure, it doesn't hurt... but can you prove it helps? My training 12 years ago said the answer was no. Has this changed?

Empirical evidence? No. Anecdotal? When I ran in the Flower Gardens, we sold nitrox for an additional $65 for a charter, or something like that. What I noticed was that with we sent about 8 divers per year to the chamber. I also noticed that with a single exception, every one of those divers were on air. Fast forward to when I chose to include nitrox in the charter price. Suddenly, everyone was on nitrox. Those few holdouts are offered a "discover nitrox class", in which all aspects of the nitrox course are taught, but a card is not issued, nor does any money change hands. Since I created that policy, I can count fewer than 10 customers who still chose to dive air, for their various reasons. I can count fewer still the number of bends cases we've had since then. That would be 2, both divers buried in deco on trimix rebreathers, which doesn't really count.

So, for recreational diving we've dropped our number of bends cases from 8 per year to zero since 2008. I'd call that pretty good anecdotal evidence.

 

[chrpai]

Can I ask what training stated that?

PADI. My manual is long gone but I just stumbled across a thread from 2006 where a poster said that on page xxx of their 2004 edition manual that it said something to the effect of it's not safer in terms of DCS. (p.16-17 in the PADI Enriched Air Diver Manual Version 2.1) If someone has a recent manual and can post the relevant information, that'd be great.

I'm not arguing one way or the other. I'm just recalling what I was told.

 

[DevonDiver]

2 dives a day isn't worth it.

I spent most of last week doing 2 dives per day.... pretty much square-profile (wreck) ~30m/90ft. Nitrox made a very beneficial difference to the repetitive and multi-day dive times.

 

[chrpai]

2 dives a day isn't worth it. If you're on a liveaboard doing 5 dives a day its money well spent.

I typically do 1-2 dives a day here. Sometimes 4. My only liveaboard experience is blackbeards (air only) and it's not a big deal because you pretty much wash out to an A diver after every dive. The Bahamas are fairly shallow and the boat is fairly slow at both relocating and filling tanks.

 

[Bopper]

It's an obvious conclusion.... but as far AFAIK there is no evidence to support it. Maybe that is out dated but I doubt it. You could probably get just as good if not better results by being very dutiful at executing proper ascent rates and stops.

For what it's worth, this weekend in Long Beach I went to a seminar on Rebreathers. Incidentally the lecturer mentioned that he could get 4 times the amt of bottom time on a Rebreather without violating NDLs than an open circuit diver. When I asked how exactly that can happen (Nitrox vs Trimix) he said it was all based on increasing oxygen levels vs nitrogen levels (effectively a multi-level Nitrox). So I guess if there are rebreather divers out there diving 4 times as long as open circuit divers without going into deco, that's pretty good evidence that Nitrox does matter. (Lecturer was Dr Jeffrey Bozanic)

 

[MXGratefulDiver]

2 dives a day isn't worth it. If you're on a liveaboard doing 5 dives a day its money well spent.

It depends ... for me it can be worth one dive a day, due to the dive profile I like to dive. Even with EAN32, I can often send myself into deco going no deeper than 80 fsw ... but because I'm using EAN32, I will often clear that obligation before I get back to 20 fsw ...

... Bob (Grateful Diver)

---------- Post added June 10th, 2013 at 12:51 PM ----------

PADI. My manual is long gone but I just stumbled across a thread from 2006 where a poster said that on page xxx of their 2004 edition manual that it said something to the effect of it's not safer in terms of DCS. (p.16-17 in the PADI Enriched Air Diver Manual Version 2.1) If someone has a recent manual and can post the relevant information, that'd be great.

I'm not arguing one way or the other. I'm just recalling what I was told.

Can't really say without context. If you plan your dives around NDL, then that's a correct statement. If, on the other hand, you plan your dives around time and depth ... and keep those the same for EANx that you do for air ... then it's not a correct statement.

Nitrox really won't do much for your DCS risk if all you're doing is extending your dive profile to reach the same NDL level you were diving with air ... because you'll still be ongassing the same amount of nitrogen. You'll just be taking longer to do it ...

... Bob (Grateful Diver)

 

[windapp]

Another "Why do I have to be certified" post.

You have to take the course to gain the certification in order to get Nitrox fills.

Why can't somebody give me Nitrox fills without the course?

Because if you die making a mistake, your family would sue the person who sold you the fill in a court of law, and win. The only defense against such a lawsuit is proof of due-diligence. In this case, proving due-diligence is showing that they had evidence that you knew what you were doing. The only evidence that is going to stand up in court is showing that you showed evidence of being certified by a qualified body.

 

[MXGratefulDiver]

For what it's worth, this weekend in Long Beach I went to a seminar on Rebreathers. Incidentally the lecturer mentioned that he could get 4 times the amt of bottom time on a Rebreather without violating NDLs than an open circuit diver. When I asked how exactly that can happen (Nitrox vs Trimix) he said it was all based on increasing oxygen levels vs nitrogen levels (effectively a multi-level Nitrox). So I guess if there are rebreather divers out there diving 4 times as long as open circuit divers without going into deco, that's pretty good evidence that Nitrox does matter. (Lecturer was Dr Jeffrey Bozanic)

... it's due to the fact that on a rebreather you generally dive a constant PO2. With an open-circuit diver using nitrox, your PO2 level varies with depth. A rebreather diver can extend their NDL's by diving a constant PO2 of, say, 1.2 by constantly changing the oxygen level in the breathing mix. Over the course of the dive, they're diving an overall higher O2 level than the OC diver ... therefore they can stay down longer before reaching NDL. They are, however, also increasing the potential for O2 problems related to single-dive or 24-hour limits because of the higher constant PO2 levels.

Again, it's a trade-off ... and whether or not it benefits you will depend entirely on the profiles you're planning to dive, as well as how many dives per day you are planning to do. For the rebreather diver, the trade-off will usually show up on multi-dive days when they start running into their 24-hour O2 limits.

... Bob (Grateful Diver)

 

[tplyons]

Reason to do the course? Get the c-card so you can get fills.

Yes, you can learn everything outside the classroom, but you can't get Nitrox without the c-card.

Instructors at my dive shop go above and beyond. They even include top level overviews of oxygen cleaning, how Nitrox is manufactured, etc. Not quite Gas Blender, but touches on a few of those principles that you won't see until then.

 

[boulderjohn]

There were two points related to the PADI statement about not being safer in regard to DCS.

1. If you dive nitrox to the limits, it is no safer than diving air to the limits.

2. If you dive nitrox on an air profile, yes, it is safer, but to a statistically insignificant degree. The percentage of recreational dives on air that result in DCS rounds off to zero. While doing those same dive profiles on nitrox is safer, it still rounds off to zero.

The point was that the purpose for diving nitrox is to extend bottom times, but if you do so that takes you to the limit, then it is no safer than diving on air.

Remember that years ago, the prevailing thinking on nitrox was that it was so very dangerous that recreational divers should never use it. Today we have almost reversed that thinking.