lol ... excellent point.mempilot:
02 on non deco dives
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HI Mempilot....
That was interesting, but in reality it didn't pass the smell test right away anyway, given the profiles.
I didn't believe it, so I ran the first day as a sense-check. Then I read the posts since
I guess I'm just not buying the whole reason to use 02 on a recreation NDL dive,....period.
Add complexity, for zero good reason. All it's really doing IMHO is adding grief to fix/help a perceived problem that isn't really there.
We all know, or should, that Mem's dives could easily be done on EAN32, without overshooting anyone's NDL, and infact they do not even require a mandatory deco stop given proper ascent rates.
S0 I ask the original poster,..WHY 02 in the first place? What are the problems trying to be overcome, because I don't see them?
Regards gents.
Steve
That was interesting, but in reality it didn't pass the smell test right away anyway, given the profiles.
I didn't believe it, so I ran the first day as a sense-check. Then I read the posts since
I guess I'm just not buying the whole reason to use 02 on a recreation NDL dive,....period.
Add complexity, for zero good reason. All it's really doing IMHO is adding grief to fix/help a perceived problem that isn't really there.
We all know, or should, that Mem's dives could easily be done on EAN32, without overshooting anyone's NDL, and infact they do not even require a mandatory deco stop given proper ascent rates.
S0 I ask the original poster,..WHY 02 in the first place? What are the problems trying to be overcome, because I don't see them?
Regards gents.
Steve
The thread started with a simple question. Some of the answers were simply a stage gas (O2 or some other EAN mix) always helps reduce the nitrogen load if one wants to use it ... not that it is required. The fact that an NDL is not exceeded does not mean that a stage gas won't help ... or that DCS will be avoided.Scuba_Steve:
My sentiments exactly. Why do it?
Scuba_Steve:HI Mempilot....
That was interesting, but in reality it didn't pass the smell test right away anyway, given the profiles.
I didn't believe it, so I ran the first day as a sense-check. Then I read the posts since
I guess I'm just not buying the whole reason to use 02 on a recreation NDL dive,....period.
Add complexity, for zero good reason. All it's really doing IMHO is adding grief to fix/help a perceived problem that isn't really there.
We all know, or should, that Mem's dives could easily be done on EAN32, without overshooting anyone's NDL, and infact they do not even require a mandatory deco stop given proper ascent rates.
S0 I ask the original poster,..WHY 02 in the first place? What are the problems trying to be overcome, because I don't see them?
Regards gents.
Steve
I take my O2 bottle on some of my deeper NDL dives now. Plus I take a long time to do that last 20' - 6 minutes. With my single 125 weighing in at 58 pounds juiced up at the comex of the dive, the little teeny 40 doesn't weigh anything anyway.
I always plan lots of contingent profiles on a dive to begin with, so I almost always go into deco anyway. Gotta maximize that bottom time when ya can.
My body pretty much hates all the physical stuff I do to it now, and enjoys letting me know about it and it likes the pure O2 sojourn. It's really going to get upset when I start kitesurfing this winter, so I have to be nice to it.
If I was still 20 or 30, or I guess even 40, I wouldn't bother.
I always plan lots of contingent profiles on a dive to begin with, so I almost always go into deco anyway. Gotta maximize that bottom time when ya can.
My body pretty much hates all the physical stuff I do to it now, and enjoys letting me know about it and it likes the pure O2 sojourn. It's really going to get upset when I start kitesurfing this winter, so I have to be nice to it.
If I was still 20 or 30, or I guess even 40, I wouldn't bother.
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Boomer7
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mempilot:
It seems that over the past few days this thread has gotten alot of exposure. As I stated before I have no intention of using O2 on a 30 minute dive to 40 ft. now on a nice dive to 110 - 130 foot range I will probibly bring that O2 along. The thing that is bothering here is that some people feel that the dive would then become more complicated. Every single person posting to this thread has started thier diving career with a single 80 filled with air. From there we have progressed to steel tanks, drysuits, Nitrox, over head environments, Doubles....ETC The diving has become complex but it has also become the norm. I am not trying to blaze a new trail here. Ten years from now CCR will be norm and we may all be breathing trimix. MY origional question was posted to help me decided if the benifits of O2 during a safty stop is worth the extra work. MY plan is not to just jump in the ocean with my doubles and O2 and just wing it. I have every intention of planing my dive and diving my plan.
BR
Going on pure oxygen for only three minutes is almost giving the diver no benefit at all on relatively shallow, shorter recreational dives. Run the same dive with and without the oxygen and you will hardly see any benefit in run time, if you are trying to get out of the water faster, or offgassing, if you are trying to increase your safety margin. This is because it takes about two minutes for the oxgen to travel one circuit through the blood stream and tissues.
Often in these kinds of circumstances, the diver can be just as well or better served by carrying out a longer safety stop on the back gas with a slow ascent thereafter. Alternatively, if oxygen is to be employed, then the diver would be better served by going on for a longer period, like five minutes, and then continuing to breathe oxygen for some time after surfacing in order to facilitate faster offgassing as bubbles form after reduced ambient pressure. It all depends on everything in the profile.
So I again return to saying, why bother adding task loading, dragging additional equipment around in possible heavy current situations and then bother with it when it is giving a very limited benefit to the diver in the first place? Yes, when you start increasing bottom times, depths and other parameters, then it can make sense (like doing a long 60 foot dive on air, etc.) to employ oxygen to speed up offgassing and increase safety margings. It all depends on all of the issues: depth, time, conditions, hassle factor, number of dives over a given period, etc.
Often in these kinds of circumstances, the diver can be just as well or better served by carrying out a longer safety stop on the back gas with a slow ascent thereafter. Alternatively, if oxygen is to be employed, then the diver would be better served by going on for a longer period, like five minutes, and then continuing to breathe oxygen for some time after surfacing in order to facilitate faster offgassing as bubbles form after reduced ambient pressure. It all depends on everything in the profile.
So I again return to saying, why bother adding task loading, dragging additional equipment around in possible heavy current situations and then bother with it when it is giving a very limited benefit to the diver in the first place? Yes, when you start increasing bottom times, depths and other parameters, then it can make sense (like doing a long 60 foot dive on air, etc.) to employ oxygen to speed up offgassing and increase safety margings. It all depends on all of the issues: depth, time, conditions, hassle factor, number of dives over a given period, etc.
I have to disagree that O2 doesn't give a significant benefit. Again, while I can respect the choice to not carry the equipment, those that do are getting a nice benefit and it is not simply an exercise in futility. The circulation time doesn't matter since it will still circulate. A 3 minute stop on O2 can give the same benefit as 10 to 17 minutes minutes on air. It is known that a safety stop is beneficial and should probably be considered mandatory. So why not do some significant offgassing and use an enriched mix. The goal is to get out as clean as possible and if I'm going to do a safety stop, I want it to be as beneficial as possible. So any enriched gas will help. While numbers can be crunched in a variety of fashions, a reality check still shows that there is a definate physiological advantage. While it may not be necessary to beat DCS all the time, there are more benefits than just beating DCS. Again, I'm not advocating that this is neccessary, but for those that want to, the benefit is real.
robinsonboomer:
Actually, I started diving with a steel 72. I still regard AL80's as a passing fad.
But I agree with you, doing 40%, 50% or even 100% O2 at the end of the dive is not any more complicated than slinging a pony and doing a reg switch at the appropriate depth. It is something any Nitrox or Adv Nitrox trained rec diver could easily handle. The diver needs to be aware of and consider OTU's, but in practical terms on the short exposures encountered on recreational NDL/saftey stop profiles, a diver is virtually never going to find it to be a limitation.
The complexity argument has me confused because oddly enough, if you look at threads on how to carry a pony bottle, everyone is stating how easy it is to sling a pony compared to backmounting and pointing out how they essentially dissapear in the water, are easy to use etc. Here however the idea of slinging a deco bottle is suddenly overly complex, adds drag, etc. A little consistency would be nice. I don't think whats in the bottle makes all that much difference.
And again, if you fill it with 50% you also have a bailout at depths of 70 ft. or less so it is more than just dead weight on the dive.
DA Aquamaster:
If there is no difference in carrying one, is there a difference carrying two? How about carrying two 40s and also an 80 to use as a stage. Carrying more equipment adds a level of complexity as well as additional physical stresses to the diver. Not that it is insurmountable (thus the statements of how easy it is and how it practically disappears) but it does add factors.
Swim through the water with a single tank on your back. Next, change to doubles. There is a difference in the amount of effort required eventhough you are perfectly neutral. Add a slinged 40. Another effect on drag and effort and gas consumption. Add another: still more effect. Carrying this equipment must be balanced against the dive mission, safety and the benefit of its use.
Please don't get me wrong here. When I do dives beyond 200, you know I am carrying at least double 120s and two 40s for the ride back up. This is fully warranted and necessary. However, in that case, there is quite an involved dive plan when compared to doing a shallow recreational dive that can be safely and easily conducted with a single mix. There is also quite a lot more effort to the dive. In that case, it is worth it.
More is not always better under all circumstances. The consistency you ask for comes in how you approach the decision, not in always using the same equipment not matter what the dive.
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