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

[kanonfodr]

I'm not a tech diver, so this may be a learning moment for me, but at 25% EAN that 616 mentioned, and a P02 of 1.4, wouldn't that allow for a max depth of 151, and if you push it to 1.6, a max depth of 178?

Again, it's not an area I play in, just curious...

The issue isn't just O2 toxicity at depth, it's the narcotic effect of breathing Nitrogen under those pressures, as well as the higher Work Of Breathing a nitrogen-based gas vs a helium-based gas, say 21/35, 18/45, or 25/25. Helium is great about reducing both Nitrogen Narcosis as well as WOB issues associated with deeper diving.

Peace,
Greg

 

[BKP]

The issue isn't just O2 toxicity at depth, it's the narcotic effect of breathing Nitrogen under those pressures, as well as the higher Work Of Breathing a nitrogen-based gas vs a helium-based gas, say 21/35, 18/45, or 25/25. Helium is great about reducing both Nitrogen Narcosis as well as WOB issues associated with deeper diving.

Peace,
Greg

Thanks...

Figured there must be other issues to deal with -- had no idea Work of Breathing was a shifting variable for different gases...

 

[616fun]

I'm not a tech diver, so this may be a learning moment for me, but at 25% EAN that 616 mentioned, and a P02 of 1.4, wouldn't that allow for a max depth of 151, and if you push it to 1.6, a max depth of 178?

Again, it's not an area I play in, just curious...

I'm not a tech diver, so this may be a learning moment for me, but at 25% EAN that 616 mentioned, and a P02 of 1.4, wouldn't that allow for a max depth of 151, and if you push it to 1.6, a max depth of 178?

Again, it's not an area I play in, just curious...

Most tech divers manage average depth ratings once they reach their max and shoot for an exposure of around 1.2 ppo2. While you might dip down to 150' you wouldn't want to execute the entire dive at that depth with 25% mix. As someone else mentioned you would want to manage your overall oxygen exposure. Pushing your ppo2 to 1.6 would occur at your deco stop (50% @ 70' 100% @ 20' etc). For really long decos you would introduce air breaks to reduce overall O2 exposure.

I should also mention I'm typing on my phone and had a few too many beers so anything I misstated I'm going to call drunk fingers

 

[Rich Keller]

If you want to read that study, its in the post Rainer made.

Your tolerance test isn't a valid test, that's the moral of the story. It makes no sense to test people for tolerance to hyperbaric oxygen because there is HUGE intrasubject variability. You don't gain anything by testing. Passing the test once has nothing to do with passing it again, and failing it once has nothing to do with failing it again. Its a crapshoot.

Just because the Navy manual says something, that doesn't make it true. Blindly following something is one of the WORST things you can do.

Blindly following the US Navy Diving Manual is the worst thing I could do????? Are you suggesting you know more and better then they do????? All you know is what you have been told by other people as arrogant as you seem to be. I will stick with what the Navy has to say!

 

[Elvistheking]

Blindly following the US Navy Diving Manual is the worst thing I could do????? Are you suggesting you know more and better then they do????? All you know is what you have been told by other people as arrogant as you seem to be. I will stick with what the Navy has to say!

Blindly following anything is the worst thing you can do, no one really knows how Oxygen toxicity occurs no one really knows how decompression works, and that includes the US navy, so you educate yourself, be a thinking diver and make your decisons.

One thing to consider, how many dives a year do you think US navy divers make a year in total, how many dives do divers from the main rec/tech agencies make a year? Hell I'd be willing to bet the divers on this board make more dives a year than the US navy do.

 

[gypsyjim]

When I first certified the Navy Dive Tables were the only game in town. It was all there was, but a lot has been learned since then, which has showed that those tables could easily get a diver killed if they blindly followed them. They were useful, but much more has been learned, and many corrections and adjustments have been made, through real world experience, and continuing research, making the dive world safer.

 

[gypsyjim]

 

[PfcAJ]

Blindly following the US Navy Diving Manual is the worst thing I could do????? Are you suggesting you know more and better then they do????? All you know is what you have been told by other people as arrogant as you seem to be. I will stick with what the Navy has to say!

If what the navy says doesn't line up with the science, then something is wrong. The simplified view of oxygen that you hold is the weak link. I bet you still haven't read any of those studies.

And no, I've done a fair bit of research, talked to many people, and done some diving myself to reach the conclusions of how I dive. And if something more compelling was presented, I'd change. I've done that plenty of times, and I'll do it again.

 

[boulderjohn]

I'm a little confused about the quote from the NAvy manual:

"NITROX breathing gas mixtures are normally used for shallow dives. The most benefit is gained when NITROX is used shallower than 50 fsw, but it can be advantageous when used to a depth of 140 fsw.

Advantages and Disadvantages of NITROX Diving.

The advantages of using NITROX rather than air for diving include:
Extended bottom times for no-decompression diving.
Reduced decompression time.
Reduced residual nitrogen in the body after a dive.
Reduced possibility of decompression sickness.
Reduced Nitrogen Narcosis

The disadvantages of using NITROX include:
Increased risk of CNS oxygen toxicity.
Producing NITROX mixtures requires special equipment.
NITROX equipment requires special cleaning techniques.
Long-duration NITROX dives can result in pulmonary oxygen toxicity.
Working with NITROX systems requires special training.
NITROX is expensive to purchase."

The above quote is from the US Navy Diving Manuel. I will try to attach a copy but it is a big file so it may not work.

To be clear they did NOT tell me it could not be used at depth just that the increased risk far out weighed the benefits. Which brings me back to my original question. Is anyone giving oxygen tolerance tests to people before they take a Nitrox class?

PS: The file did not seem to attach. I can email a copy to anyone who would like one.

I don't see anything in there that seems to be inconsistent with what most people are saying. It looks a lot like what is taught to even beginning divers in recreational nitrox courses. I would quibble with some points, but it would be merely quibbling.

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.

 

[Ana]

I'm a little confused about the quote from the NAvy manual:



I don't see anything in there that seems to be inconsistent with what most people are saying. It looks a lot like what is taught to even beginning divers in recreational nitrox courses. I would quibble with some points, but it would be merely quibbling.

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.

There is no confusion... Navy website has the Diving Manual available for download.

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.

I'm HOOYAH NAVY!!! all the way, they pay my bills, but even acknowledging that they are not poo pooing NITROX I wouldn't follow their manual blindly... their Diving Command does not jump to edit their manual every time NEDU finds something new in their trials.