Nitrox Question

[fnfalman]

Wow! That's a pretty declarative statement. Want to justify it?

My dive computer automatically sets the Nitrox mix level to 21%, otherwise known as "air," and if I'm diving with a different mix, I set my computer to register that percentage. I learned the recommended dive limits for the various standard mixes out of the book. Learned how to measure the mix level in the class, using an oxygen analyzer (but not the one I have encountered most frequently on trips). Learned in the class how to record the necessary info on the tank and in the log book for each dive. Then, I started diving with Nitrox. What, exactly, does the actual underwater part of the dive accomplish for the use of Nitrox that above water tutelage does not?

Yep. Once you do the theories and learn how to use the gas analyzer, it ain't no different than diving on air except that your MOD changes. Jesus H. Christ, it ain't rocket science.

It doesn't change how I handle my buoyancy. It doesn't change how I kick my fins. It doesn't change my safety stop procedures. It doesn't change anything but my bottom time and depth, which changes with air anyway depending on which dive of the day and to which depth.

 

[ScubaDocER]

Wow! That's a pretty declarative statement. Want to justify it?

My dive computer automatically sets the Nitrox mix level to 21%, otherwise known as "air," and if I'm diving with a different mix, I set my computer to register that percentage. I learned the recommended dive limits for the various standard mixes out of the book. Learned how to measure the mix level in the class, using an oxygen analyzer (but not the one I have encountered most frequently on trips). Learned in the class how to record the necessary info on the tank and in the log book for each dive. Then, I started diving with Nitrox. What, exactly, does the actual underwater part of the dive accomplish for the use of Nitrox that above water tutelage does not?

I don't really have to justify it, it's just my opinion. But I will be happy to elaborate on why I feel that way. Part of my beliefs were stated in an earlier post regarding the difference between theoretical teaching and real world applications. Diving is an active sport. The theory is nice, but you need actual in water experience to appreciate the theories that are taught in class. Technically you don't need an Instructor to do any diving. There are people who have been diving for years who never received a certification from any agency. In today's diving environment however, Instruction can be life saving for many new divers. The in water education under the guidance of an Instructor does not equate to hand holding, but to guidance and education. When I teach OW students, I am not holding their hands. I guide them away from making mistakes and how to deal with some common unforeseen problems. Nitrox is no different. What if your vaunted computer dies on you? What if the blenders computer is wrong? (Which is why we teach you to analyze your own mix). I have had 2 blenders make mixes for me that were off by 2%. I have had a blender ask me to sign the log book before he analyzed my mix. While an Instructor cannot prevent every possible scenario from occurring, their wisdom can certainly steer you away from potentially life threatening mistakes that divers can make, or educate them on how some people short cut the rules. The issue for me is not CAN you dive with Nitrox without an Instructor present on your first dive, but SHOULD you do so. It remains a personal choice for the student diver and their desire to seek the best education possible. If they feel that that is achieved in the classroom better than in the water, then so be it. As an Instructor, I feel differently. By the way, it seems that most certifications with "diver" in them require an actual dive. OW, AOW, Rescue, Deep, Night, U/W, Master Scuba (for NAUI anyway), etc. I assume there are some that do not. It seems odd to me that Nitrox diver would be the one exception where you don't have to actually do a dive.

 

[ScubaDocER]

I have to disagree with you scubadocer; there's no reason to do a dive with an instructor when using nitrox for the first time IMO.

Your points just don't make sense. According to your reasoning a diver would need an instructor along everytime they deviated from their SOP. If you need an instructor to hold your hand so you won't violate a MOD you shouldn't be diving period without a DM much less on nitrox. As far as analysing at the divesite... I don't know anyone who does it recreationally. We analyse at the shop and put a MOD/% sticker on it. Having an instructor go along on the first dive to help one "recheck" it is a bit... much (and assumes one has purchased their own gas analyser. Quite a rarity for someone just doing a nitrox course).

Nitrox is just air with a bit more oxygen added. You can't compare it to Trimix. One is recreational, the other is technical.

There are some important factors that one must learn about its properties and effects and then incorperate into a dive plan true, but all that happens on the surface. Once one descends one should be following the plan made on the surface (which is not a skill covered by the nitrox course). What you are suggesting is that a nitrox instructor is needed to ensure one can follow a simple dive plan. That smacks of remedialism.

--------------------------------------------------

What I like about the nitrox course is that it forces you to think about MOD's, gas physiological effects, OPP's, using tables etc... Information that is important whether one dives nitrox or not. It gets your brain thinking differently (critically) about the gas you're breathing.

Hello Dale. I can respect a differing opinion. I tried to address some of what you commented on in my previous post but will try to address any that I missed. Again, I don't believe that you need an Instructor to hold your hand every time you get in the water. It seems intuitive to me that at least one dive be done under the guidance of an Instructor. If your Instructor (who is signing off on your card stating that you understand how to safely use Nitrox) feels comfortable with your performance, then they sign you off and you go about enjoying the benefits of Nitrox. I actually analyze my mix at the dive site before every dive and teach my students to do so as well. As mentioned earlier, I have had shops give me mixes that were not within 1% of my desired mix. It happens. People are fallible. Sometimes the blender forgot to calibrate the analyzer. But students are responsible for the gas they breathe. If they are not proactive about that, then mistakes will occur. Purchasing an analyzer is not necessarily a rarity. If you take your life into your own hands by breathing Nitrox, then having an analyzer is not unreasonable if you understand the consequences. I don't believe that it is mandatory to have one. But I do believe it is prudent to do so and have seen many divers who concur. It depends on how much you trust your blender.

Nitrox is a little more than just air with oxygen added to it. That's the theoretical aspect of it. The real world application is that Nitrox introduces MODs to the diver that are not applicable with recreational divers who use air. It requires more awareness that the air diver might experience. Seizing underwater is never a good thing. While an Instructor cannot prevent every mistake from occurring, helping a student to appreciate this awareness underwater may be life saving. Remember, these are still students in a Nitrox class. They are taking the class to understand not only the theory of Nitrox, but it's application. Students make mistakes. Instructors should be able to assist with the correction of those mistakes. I can understand students who don't think they need in water education to dive Nitrox. Sometimes students feel they are invincible or that they "get it" when in reality they may not. I guess I am puzzled with Instructors who should know better and choose not to get in the water with their student to review and assess in water understanding and comprehension of concepts taught in class. By the way, I review the dive plan in all my classes, Nitrox included, before we ever get into the water. If it is not a skill taught or reiterated at the surface, it should be. Just my opinion.

 

[Orlando Eric]

I generally support check out dives. I am against the zero to hero shops who take a non diver to instructor in a short burst of classes. There are shops who even do several minmum depth / time dives to bump up the number of dives required.

My personal experience with my nitrox class. I had 100's of dives spanning many years. I am above the "C+" populace average in the learning curve but no genius. I read the material several times and had a firm grasp of the science.

Why would an instrucor need to be present for check out dives without new diving techniques having been taught.

I point to a well known AIR diver on this board. Debby Diver. AFter the classroom and homework is completed I am certain she would be able to figure best mix, MOD and O2 loading. I have no doubt Debby's diving technique is in the top 10% of the broad range of certified divers.

Do I think check out dives should be requred? No. Is it a big deal if they are? No.

I am for diving. I love diving. Guided dives are even better. Diving with someone like Walter or Kevin I am certain to see or learn something new even after almost three decades of diving.

TO the original OP. Take the classes. You learn stuff about diving which will give you a better grasp about diving gas under pressure including air. I learned A LOT about diving in my OW class. Very little in AOW and specialty classes. Quite a bit in Rescue and A LOT in my DM class.

I would highly recommend Nitrox and Rescue to any diver who plans to dive more other than a one time trip to the resorts.

PS- Analyizing tanks. Whenever possible I drop my tanks off a day ahead of time and check them the next day. I am not 100% convinced you can get a good reading off a tank which has just been partially blended. Banked mix like Fill Express is great for fill and go diving.
There is another concern with tank fills. Unless you know the fill rig at the shop and watch the tank monkey fill it are you willing to bet your life on the whip he used to fill it?? If you do not check the fill... you are.

 

[diverrick]

My wife and I got our Nitrox with our advanced certs. I thnk it was less than 100 bucks per person. These are only my opnions here, but we know it gives you longer bottom times within the limits of the MOD, It gives you shorter surface intervals, which REALLY come into play on livaboard s where you routinly dive 4 to 5 times a day. Compared to the "air" divers, We feel safer about not getting bent, as we have less Nitrogen in our systems compared to them. Especially as older divers, less chance of getting bent is a good thing.
I have consistantly seen air divers working right up against thier Deco limits on every liveaboard I have been on. Nitrox divers don't get anywhere close using the same profile and number of dives. We feel we feel less tired after a day of heavy Nitrox useage. We think we have less Cotton mouth on Nitrox as well. I do not think a check out dive is needed if all your training on is Nitrox. If there is something else your training on at the same time, then a dive might be appropriate, but for Nitrox? Nope!
The only thing you do differently under water is don't exceed the MOD. Everything else is topside stuff, like analysis, dive profiles, determining the MOD, expected limits, Etc. Placebo effect, I don't know about, but using extra O2 during diving, can only be a good thing as long as you stay within your limits. We dive exclusivly on Nitrox. We did 30 dives to around 80 to 100 feet in one week, a couple of weeks ago. Try that on air and see what your tables and computor tell you. Most of this is subjective from my experience, and some of it is fact. IMHO

 

[Peter Guy]

Why not add my 2 cents (not that this is worth 2 cents!).

a. EVERY dive has an MOD that one should not violate -- it is just that the MOD of some mixes (21% Nitrox!) is deeper than most people want to dive so it isn't terribly relevant. But, neither is the MOD of 110' on a 70' wreck. Staying abover the MOD is only relevant when the diver CAN get below the MOD which is NOT true on every dive -- just as staying above the magic 60', 100' or 130' "certified depth levels" is only relevant on those dives where the diver CAN go below those magic numbers. In each case, the gas you are breathing is not the issue -- it is the awareness -- although I will certainly admit that the consequences of going below "X" depth may be more significant when breathing EAN (but maybe not depending on a whole host of other factors). Depth awareness is its own issue.

B. Do you really, honestly, care that your mix is 1 or 2 or 3% off your request? Me, all I care about is knowing what the mix is and THEN knowing my 1.4MOD -- that tells me what my dive limits are. I admit I tend to put in a pretty significant fudge factor and stay well above my 1.4MOD -- in fact, 100' on an EAN mix is pretty much my limit.

C. Doesn't every agency teach that you should analyze your own mix? I've never used a tank I (or someone I REALLY trust, aka my wife --- hmmm, well now that the life insurance has lapsed I REALLY trust) haven't analyzed. I may not have physically held the analyzer, but I've been shoulder-to-shoulder with the person holding it and confirmed the readings. And I've never picked up a tank from my LDS that I haven't analyzed -- the shop doesn't, I do -- so what's with re-analyzing at the divesite?

Conclusion -- taking away the dive from the EAN course makes sense -- BUT, if you are going to do the Dives, they should be buoyancy control/depth awareness dives. Hmmm, perhaps EAN certs should be paired with PPB type certs -- two for the price of one!

 

[TSandM]

If you have picked up tanks that have been partial pressure blended right before you got them, the end mix may be somewhat higher than what you get in the shop. If you are planning to dive right to the MOD of the gas (especially, for example, deco gases which may be dived at 1.6 ppO2) I could understand reanalyzing at the dive site.

Most of the time, my tanks were filled a day or more before I pick them up, and I rarely push my MODs, so I don't reanalyze before diving them.

 

[lmorin]

.....................
B. Do you really, honestly, care that your mix is 1 or 2 or 3% off your request? ..........
...........

That's actually an interesting issue because there is a technical piece to the answer. The "mix percentage" actually is one of 3 different possibilities--the real mix, the desired mix or the measured mix. They are 3 distinctly different realities. The desired mix is pretty clear, as it is the mix intended by the person filling the tank. What is actually put in the tank is almost certainly going to be different because the mix will only be as accurate as the technology allowing the mix. The third reality, what the diver perceives as the "measured mix," is likely to be the most problematic. It is anybody's guess whether the O2 analyzers are still accurate days, weeks or months after they leave the manufacturer (assuming accuracy there), even if set right by the user, after sitting around in heat, humidity and above usual atmospheric salt conditions. Some analyzers require the user to adjust them to baseline "air" conditions; some do not. Whether the calibration by the diver actually is maintained for a second or more tanks or not is also questionable, at least to some degree.

So, in response to your question, no, I don't care; it does not really matter. Dive and be happy!

 

[farsidefan1]

Although the placebo affect is certainly well documented it relies upon an expected result. I had no idea that nitrox could cause this more "energized state of being. I had no anticipation of said effect. It wasn't till the divemasters comments that I realized I wasn't experiencing something unique. No expectation rules out placebo effect. The mind isn't that powerfull. I don't believe in shared memories! Furthermore it isn't something noticed after one dive but several dives. I'd have to see the double blind study ot see if it involved repetitive diving over multilple days. Nonetheless, my original statement stands on its own, no expected outcome, no placebo effect, period.

Why do you believe the effect of a placebo cannot be significant? To date, there's been one double blind study of this feeling of being less fatigued diving with nitrox. The results indicate it is a placebo. There is room for more study, but until that happens, there's no reason to believe it is anything other than a placebo - the mind is a powerful thing.

 

[Walter]

Excellent point! On the other hand, you might not consciously remember having heard about nitrox reducing fatigue, but do remember hearing about it subconsciously. You've also probably seen football players breathing oxygen on the sideline. It's quite easy to connect that with nitrox. The anticipation doesn't have to be conscious. By the way, oxygen has not been shown to be of any benefit to football players either.

As for single dives vs several dives, some agree with you, others feel better after one dive, others feel no difference at all after a single dive or multiple dives.

Double blind study.

As I said before, There is room for more study, but until that happens, there's no reason to believe it is anything other than a placebo. On the other hand, if it works for you, it works, placebo or not.