02 on non deco dives

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DepartureDiver:

I think the thing the guy originally posted was NDL dives. Only NDL dives. I am speaking on that point only.

So again, you're simply not going to use, nor do you need this supposed 10 minutes (And heaven forbid 17!!! who's NDL limits we running!! :) )of deco "savings". You didn't need it in the first place, since we're speaking directly about NDL dives.

Sure 02 will help, but it is of so limitted use, there's simply no sense. The guy is trying to fix something that isn't broke.

I should say I guess, he's not really trying to fix, just asking if it would help. Well yes, technically, but not near enough to waste carrying it around.

As for DA's comment about it being difficult to use......we'll sure it's not, but the point long before this, is, again, why bring it? And WHY are you requiring bailout gas? Where's the buddy, where's the gas plan? Where's the sense?

This is again why I hate seeing folks using these things on NDL recreational dives. It only re-inforces that "I've got more gas now so I can.......<fill in the blank>...." type of thiking.

The pony goes from "reserve" to hey' lets use this for extended time.....heck I can sling 50/50 or maybe more EAN32!! Yeehaaa. Buddy?? what buddy.......what's a gas plan???

It totally f**ks people up in so many ways.

The KISS rule, rules. Take what you need, plan the dive, leave the crap you don't need on the boat. Rec NDL's simply do not need extra junk trying to make them look hi-tech and cool.

Been there, done that, I see how dumb it is. I was such an idiot :) Why didn't Mem slap me?

Good posts too ScubaDad!

Good thread folks. I think I'm going to point some people I know in this direction (Everybody wants a pony).

Steve
 
DepartureDiver:
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 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.

Let me start off by saying that my intention is to bring about an open discussion and not to attack you or anyone that disagrees. But, I will raise a point. I will use a bit of extreme to demonstrate it but you can carry it to where you care to draw the line and then the rest of us have to respect that decision on your part. So . . .

Let's say you are planning to do a single dive to only 20 feet for no longer than 20 minutes. You have the following gas mix choices available for purposes of my point:

1. 100 percent oxygen.

2. Air.

3. Start the dive on air and then switch to oxygen for a given period, say three to five minutes, and then ascend on pure oxygen.

4. Any nitrox mix you desire either by itself or switching to oxygen as in example three above.

At the end of this dive, considering the depth and bottom time, it would be a far stretch to say that there is any "real," as you put it, benefit to one choice against the others DCSwise (see below also). Further still, carried to its ultimate conclusion, if you wanted to be even "safer," you could even oxygen breathe before entering the water until all nitrogen is purged from your system and then conduct the dive on pure oxygen. This would assure that there was no chance of inert gas problems.

In the end, you exit the water the same way after all of these dives: clean enough that DCS is not a significant factor by any modern dive calculation.

Okay, start changing depths, times and mixes. Eventually, you do get to a point where the additonal gases do add a benefit that warrants carrying them. Everyone draws the line at a different point perhaps. I can respect that. All I am bringing up is the point that there are tradeoffs to everything. Consider them all when planning your dives and then do whatever works and feels comfortable to you. Last, I am also bringing up that more is not always better.

DepartureDiver:
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.

Other than perhaps CO2 buildup, I would like to hear about what other benefits you consider.
 
DA Aquamaster:
Actually, I started diving with a steel 72. I still regard AL80's as a passing fad.
too funny … and if you get your 10% overfill you still have almost as much gas since an 80 is not even an 80.
ScubaDadMiami:
Other than perhaps CO2 buildup, I would like to hear about what other benefits you consider.
DCS is symptom driven. If you feel fine you don’t have it, but otherwise you do. However, even if one feels fine, bubbles are still present. My point is your body is being affected even if you don’t feel bent. One concern of mine is that lessons learned are being forgotten or ignored. Commercial divers started experiencing dysbaric osteonecrosis, yet tech divers now seem to pride themselves on how fast they can decompress … but what about the possible long term affects from these dives? There may be none, but I think it is too early to tell. One criticism our team initially encountered was that we decompressed too long … so you can see I approach diving from a conservative aspect. Taking it a step farther, recreational divers now like to use computers and push the limits with many not doing much in the way of safety stops. The computer years are still fairly new and can also result in nice gas loading. Upon surfacing, the divers with their nice gas loads are probably not offgassing as their half-time table or computer is assuming due to the resulting bubbles, but down they will go again since the industry through their computers are telling them it is okay and safe. So my soap box is that just because you are within the NDL’s using today’s standards of short surface interval does not mean that no damage or long term affects are being done … especially in the tech community. So even if a dive did not result in DCS where a gas switch would not be necessary, it certainly does a body good and can help with more efficient offgassing upon reaching the surface due to the significant offgassing that occurred during a safety stop. So if divers are using their heads and recognize that a gas switch has a benefit, I encourage them to do so. I always have said if divers truly understood the benefits of a safety stop and how it works, everybody would be doing them. The use of a gas switch is the same since it is simply a tool to offgas, just as the safety stop is. But I still agree that there is a point of diminishing returns and it may not be worthwhile on every dive such as the shallow dives. But I’m still going to sling my pony on all dives.
 
Well said DD. I am not the same 21 yr old Marine I was when I started diving, using US Navy tables and pushing them to the limits. At that point I had maybe 5% body fat. I have a bit more than that today and would not even remotely consider diving some of the profiles I used to dive.

So when I do 1 or 2 deep deco dives in the morning followed by 2-4 shallower (100 ft or less) rec dives in the afternoon, I like to add a few minutes of deco on the deep dives and I like having 50% along for the deep stop and saftey stop on all the rec dives in the afternoon just to add a bit more margin of saftey.

And the truth is since I started doing this I feel much better with none of the fatigue and the Monday blah feeling I used to get after a after a weekend of diving.

Pushing 40 I no longer have the huburis of youth nor do I have the ability to delude myself that table limits are absolute or that a dive computer is infallible. I know a diver who got bent on a dive trip and considered it to be an unjustified hit as she was within the NDL limits. But given factors such as alcohol use, smoking, being overweight, and being potentially under hydrated on a tropical multilevel, multi-dive, multi-day dive trip, her DCS seems to be more related to diving well outside the limits of what her computer was designed to do rather than being inside the computers NDL's. She considers her DCS hit to be unjustified, but I consider it to have been most likely preventable if she had considered what was really going on and built in an increasingly larger saftey margin over what her dive computer told her was acceptable. Reading the dive computer manual and noting it, like most others, was not designed for multi day repetetive diving would have helped a lot too. Decompression is not an exact science and there are a lot more variables involved than what your table or computer says you can safely do.

Personally, I'll take a little more saftey in exchange for a little more complexity anyday and I would encourage any rec diver to continue to increase their skills and knowldege along the way and to use any means available to dive safer.
 
Scuba_Steve:
As for DA's comment about it being difficult to use......we'll sure it's not, but the point long before this, is, again, why bring it? And WHY are you requiring bailout gas? Where's the buddy, where's the gas plan? Where's the sense?
Anyone who dives in low visibility or a potentially silty environment will tell you just how fast you can lose a buddy. I agree a buddy is nice to have but I will never put myself in a situation where my life depends on them. I belive in self sufficiency even on a buddy dive as in the real world s_ _t happens. I agree any redundant air source is complete dead weight until you need it but when you need it you need it real bad.

A pony also has no impact on gas or dive planning. You are making the assumption that all rec divers are going to start abusing a pony or sling bottle by extending their bottom time and that is an inaccurate over generalization. Some people who have cars that can do 140 mph actually do 140 mph with them. The rest of them just use the extra power now and then to get on the freeway alive and divers and pony/sling bottles are no different. Some divers are just naturally going to be stupid and irresponsible, but that is not cause to ban everyone from take advantage of something that stupid folks may choose to abuse.
 
So DA, we require more buddy awareness then. I think those of us that dive where you and I both live certainly understand what low vis is, and this doesn't give one an excuse to lose a buddy, period.

Fixing poor buddy skills doesn't require the use of a pony.

Not wanting to get off topic, but it's ironic that the one thing that hasn't made the bridge from Tech to Rec is the sad fact that most Rec divers feel they don't ever need to rely on thier buddy for anything.......now that's a sad story right there. I rely on my buddy with my life, and vis-versa.

Hanging a pony on yourself is without a doubt more gear, which means more annoyance, and when it's essentially needless, it's even more useless.

My assumption with respect to using the pony as added bottom time comes from actually seeing it happen a couple odd times, YMMV of course. :)

Dive safe gents

Steve
 
DA Aquamaster:
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.
My argument, well it's not really an argument but an opinion, has nothing to do with complexity. It has to do with knowing where your body is before and after subsequent dives by using the appropriate charts, tables, and planning. Plan it, and go for it. Just sling it, and it's irresponsible IMO. We tell divers to always follow the NDL. So a diver decides to do a shore dive that won't get them below 20 fsw. They don't look at a table because they know they can be there for a long time. They go do the dive. They are safe, maybe. But they have no idea the RN in there body. Same thing. But I doubt anyone would advocate this.
 
ScubaDadMiami:
Let's say you are planning to do a single dive to only 20 feet for no longer than 20 minutes. You have the following gas mix choices available for purposes of my point:

1. 100 percent oxygen.

2. Air.

3. Start the dive on air and then switch to oxygen for a given period, say three to five minutes, and then ascend on pure oxygen.

4. Any nitrox mix you desire either by itself or switching to oxygen as in example three above.
If I was going to do a dive to 20' for 20 minutes, I'd use air and save the money on the fill. I defineatly would not carry a pony or deco bottle, even if it was for over an hour. In that case, I would use ean36 for convenience. I defineatly, would not do the entire dive at 20' on O2, since doing a working dive on O2 at 1.6PPO2 is not advisable. Start changing the depths and times, and I would use the appropriate mix for MOD based on 1.4PPO2 with a 3 minute stop. Diving below 100', I'd consider bringing a bottle of O2, but I'd run it as a deco dive and not a NDL dive, even if I were planning on staying in the NDL. The NDL does not have anything to do with gas switches. This is simple. Why are we advocating things contrary to what is taught in the certs?
 
DepartureDiver:
One criticism our team initially encountered was that we decompressed too long … so you can see I approach diving from a conservative aspect.

DD,

I really am stunned when I hear people criticize others in this manner. As you obviously know, decompression routines are NOT A RACE. There are NO awards for getting back to the boat sooner than someone else. To use that as a point of criticism is, in a word, STUPID. :nonono:
 
DA Aquamaster:
The truth is, since I started doing this I feel much better, with none of the fatigue and the Monday blah feeling I used to get after a after a weekend of diving.

I know a diver who got bent on a dive trip and considered it to be an unjustified hit as she was within the NDL limits. But given factors such as alcohol use, smoking, being overweight, and being potentially under hydrated on a tropical multilevel, multi-dive, multi-day dive trip, her DCS seems to be more related to diving well outside the limits of what her computer was designed to do rather than being inside the computers NDL's.

DA,

Your observation about how you feel is a perfectly acceptable anecdotal observation of your use of "conservatism" factors. It works, and works well, when applied intelligently as in your case.

As for your friend, given the fact that divers can be well within the NDL limits on any given dive and still get "bent", we have tended to get away from the term "un-justified". We now describe that kind of hit as "un-expected". Just as a WAG, however, judging by your description of your friend's activities, I would have to say that you are spot on in your judgement about why it happened.

Cheers!

Rob
 

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