Nitrox!
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masterof0
Guest
One key factor to keep in mind (that was brought up by Blackwood) is that although the benefit between air and nitrox may be negligible for a single dive, as you get into repetitive dives the difference between the two becomes clear cut and the value is obvious. The key to nitrox is to understand how you are using it. If you are using it to extend bottom times, then the nitrogen loading/surface intervals remains the constant. If you use it as an additional safety factor, then over hte course of multiple dives, the nitrogen loading is reduced which is reflected in reduced surface intervals or load groups.
There is no question that ascent rate is important, and that should not exceed 60fpm (or 30fpm depending on which computer/organization/rules you adhere to) regardless of which gas you use.
There is no question that ascent rate is important, and that should not exceed 60fpm (or 30fpm depending on which computer/organization/rules you adhere to) regardless of which gas you use.
Nitrogen absobtion is what this is all about. If you dive at 40 feet long enough it will ultimately be a deco dive due to the amount of nitrogen is being absorbed by the tissue. Just like if you dive at 60 feet in a short enough window it is a no-deco dive since the tissue has not absorbed enough nitrogen to be considered a high risk. Pressure and time are the two components (Inversely related) that play into how much nitrogen is being absorbed (or not being off-gassed) through breathing
Damselfish
Contributor
Unless taking the class is a big financial burden, I'd say just take the class and don't over analyze it. It's good information to have and also reinforces some things you learned in OW. Then you have the option to use it if you want to and the info to decide.
cooperscuba
Contributor
Going to have to disagree (surprize, surprize), and make this my last post on this thread (probably last anyway) as I can see this going on and on.
You can have a low load and a fast ascent which puts you at a greater risk than a high load with a slow ascent rate. It`s not the loading what this is all about, but the release (off-gasing) of the nitrogen.
We can test this if you like; I`ll make a "high load" dive, within limits, with an ascent based on my computers readings and you make a "low load" dive with a rapid ascent. If one of us ends up in the pot, they have to buy the other a beer
)Damselfish - you`re spot on
)
Well, there is actually a lot more to it than you have mentioned, but do we really need to get into this here? Nitrogen in solution in the tissues is a factor. So is ascent rate. So is the number and volume of prexisting bubbles, including micronuclei formed through exercise. So is the so-called oxygen window (whichever definintion you are choosing to use). If you want to get into full deco theory, we can get everyone's head spinning, and ultimately it gets down to the fact that we still don't really understand it all. For the purpose of this discussion, all anyone really needs to know is that increasing the amount of nitrogen in the body does indeed increase the potential for DCS, because of all the additional reasons, including, if you insist, the ascent rate, that we can add.
masterof0
Guest
This is where the challenge in this discussion is presenting itself. When I talk about NDL, regardless of whether I am at 60ft, 90ft, or 30ft, my ascent rate stays constant. 30fpm with a 3 minute safety stop.
So if I go to 60ft for 30 seconds and do a "normal" ascent and you go to 30 ft for 200 minutes and do a normal ascent, you will be at much greater risk for DCS, not because our ascents are different, but because you have more nitrogen built up in your system to "off-gas." Now if you modify your ascent from 30 feet to account for that, then you have taken into account all of the nitrogen that you have built up....Hence you and I are saying the same thing, just in a different way.
Now that we have beat a dead horse. It is defeintely worth the time and effort to take the class. There is a lot to be learned that wasn't covered in OW.
cooperscuba
Contributor
Thought this post was in "Advanced Scuba Discussions"? Where`s the "head spinning" section?
Blackwood
Contributor
Thought this post was in "Advanced Scuba Discussions"? Where`s the "head spinning" section?
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the K
the K
Thought this post was in "Advanced Scuba Discussions"? Where`s the "head spinning" section?
Believe me, a full description of deco theory will get nearly anyone's head spinning. The responses you contradicted were actually fine for the level of the discussion. Your supposed corrections were really more in the form of additional information that really wasn't needed in this context.
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