what the different between using Nitrox and Normal Air to dive???

[Zieg]

Ok everyone, let's not start dog-piling. Obviously he's not comfortable using Nitrox and is trying to use the Navy Dive Manual to support his insecurities. Let's give him a break, he is a commercial diver, so we know he's tough. Right?

 

[boulderjohn]

I
What I do not see is what we seem to be arguing over:

1. It does not say the increased risks outweigh the benefits.

2. It does not advocate oxygen tolerance testing for those who use it.

If you look at Ch 10 Vol 2, you'll see that what richkeller quote is pretty accurate, however he conveniently left out the beautifully spelled guidelines for the use and training, including dive logs and all the micro steps the Navy likes to follow. He also put a spin in the interpretation of what the manual describes... the manual states the benefits and disadvantages, the rest was added by the poster based on HIS interpretation.

OK, I just read the entire section of the Navy manual on nitrox, and I don't see anything in there that is inconsistent with a typical recreational nitrox course, such as the one I teach. I don't see any hint of a suggestion that the risks outweigh the benefits. In fact, it appears to me that it is pretty much advocating nitrox use within the identified range. I don't see a single word about a recommendation for oxygen tolerance testing.

The section on oxygen toxicity (10.3) says that dives need to be conducted with a PPO2 of 1.4 or less, and such dives "can be conducted using the full range of bottom times allowed by the air tables without concern for CNS or pulmonary oxygen toxicity." It goes on to identify a table that if followed should eliminate any concerns for oxygen toxicity on repetitive dives.

I get that he believes the risks outweigh the benefits and that nitrox users should pay for an expensive oxygen tolerance test, but there is no validity in referring to the Navy Dive Manual for support in those positions.

 

[Rich Keller]

Two things.

1) The parameters you posted for the test are much higher than those experienced by a recreational diver. Failing that test has no bearing on how someone is going to react diving recreationally on Nitrox. Just because something works in the military doesn't mean it translates to civilian use.

2) Nitrox is not equipment intensive. Many of the same regs people use for air diving are compatible with up to 40% Nitrox. A little more care is needed to clean and maintain tanks, but it's not really that $$ intensive.

You're really trying to compare apples and oranges here.

The parameters are higher in order to show your susceptibility in a controlled environment. In other words to push the limits to the max in a controlled environment to see how your body reacts. The tables you are using do not work for everyone as everyone is different but the physics in the water are no different for the military then for the civilians. While I agree the same regulators can be used for both applications most shops charge more for nitrox overhauls with very little added cost in doing so. None of this addresses my original question though. Is anyone even considering the safety for the diver taking a nitrox course? Even if you think you know more then the Navy about this there still should be something in place to weed out the people who are at greater risk by using nitrox.

 

[Rich Keller]

To elaborate, I don't think nitrox is a safe gas for diving at that depth, I think trimix is a much more prudent gas choice!

Trimix was invented to reduce the effects of helium on your system. In short the narcoses effect of nitrogen acts as a drug to keep you from shaking while on a helium oxygen mix. This is used in very deep dives and not really recommended for scuba. Trimix also has a lower percentage of oxygen then normal not a higher percent as with nitrox.

 

[PfcAJ]

Rich, I think you just need to stop. So many of your posts are dead wrong. The stuff on oxygen cleaning, the stuff on nitrox, and now you're making highly questionable comments about trimix and when it should or shouldn't be used.

People have continued to provide you with scientific research, industry standards, and practical experience. You've chosen to ignore all of that and pontificate about things you (clearly) don't know too terribly much about. Unfortunately, your commercial dive experience is somewhat non-applicable to recreational scuba (to include the use of oxygen and helium). It seems like you're just trolling.

 

[DiveNav]

 

[616fun]

Trimix was invented to reduce the effects of helium on your system. In short the narcoses effect of nitrogen acts as a drug to keep you from shaking while on a helium oxygen mix. This is used in very deep dives and not really recommended for scuba. Trimix also has a lower percentage of oxygen then normal not a higher percent as with nitrox.

Are you suggesting deep tech divers go back to deep air? I'm shaking my head....

Trimix has a lower percentage in deeper depths to manage oxygen toxicity. Displacing that O2 with N2 would be equally dangerous because of the significant impairment it provides at depths. Helium is a great choice to displace the N2 as it's inert in the body and releases more easily from tissues. It's also a thinner gas offering an easier work of breathing. In recreational technical diving it has very little to do with managing the shakes.

You should start a voodoo gas thread.

 

[boulderjohn]

None of this addresses my original question though. Is anyone even considering the safety for the diver taking a nitrox course? Even if you think you know more then the Navy about this there still should be something in place to weed out the people who are at greater risk by using nitrox.

Yes, people are very much considering the safety of the diver taking the nitrox course. When nitrox was first introduced for recreational divers, many people expressed the exact same fears as you. PADI was completely opposed. But in time and with a lot of research and beter understanding those attitudes all but disappeared. They realized that people diving to the very conservative 1.4 standard are very safe, and the margins of safety so great that individual tolerances are inconsequential. If you read the Navy manual you cited carefully, you will see it saying essentially the same thing.

Here is an interesting thread from nearly four years ago in which people talk nostalgically about the early days so many years ago when people thought nitrox was so dangerous and how silly they were then.

 

[gypsyjim]

Is it just me? Somehow op sounds dangerously uninformed, and has taken an entrenched position, that no facts or science will be allowed to sway him from, which is ok for him, but might endanger some who listen?

 

[gypsyjim]

Since no one is supposed to be worried about diver safety, I thought that I would link to the 2000 SubAqua/DAN tests: The Truth about Nitrox
The entire paper is worth reading as it addresses so much of the misunderstanding of OP. The conclusions:

DAN Nitrox Workshop Consensus Recommendations

In November 2000, DAN brought together three dozen leaders in nitrox use and training from recreational and technical training associations, manufacturers, researchers, medical and legal experts, and educational institutions, under the leadership of Michael Lang, Diving Officer of the Smithsonian Institution.

The two-day workshop covered operational data, physiology, risk management, training and equipment. Although significant and worthwhile debate occurred, a higher level of consensus was reached than has been reached in similar workshops. For entry-level, recreational open-circuit nitrox diving, the consensus was:

· No evidence was presented that showed an increased risk of DCS from the use of oxygen-enriched air (nitrox) versus compressed air.

· A maximum PPO2 of 1.6 atms was accepted, based on its history of use and scientific studies.

· Routine carbon dioxide retention screening is not necessary.

· Oxygen analyzers should use a controlled-flow sampling device.

· Oxygen analysis of the breathing gas should be performed by the blender or dispenser and verified by the end user.

· Training agencies recognize the effectiveness of dive computers.

· For recreational diving, there is no need to track whole body exposure to oxygen (OTU/UPTD).

· Use of the CNS Oxygen Clock concept, based on NOAA oxygen exposure limits, should be taught. However, it should be noted that CNS oxygen toxicity could occur suddenly and unexpectedly.

· No evidence was presented, based on history of use, to show an unreasonable risk of fire or ignition when using up to 40 percent nitrox with standard scuba equipment. The level of risk is related to specific equipment configurations and the user should rely on the manufacturer's recommendations.


For an industry and a sport that is supposed to not be concerned with diver safety, an awful lot of thought and research went into those findings. Thank you DAN!