Pony Tips

[Wallowa]

Nobody in this thread was looking for an explanation of a safety stop, no clue why you went to the trouble of stating what is obvious to all certified divers, as it's something learned in the basic open water course.

I was responding to Chrisch's question of why I need a 'separate tank' [see his post] with EAN since I dive 21%.....I thought that post would have been obvious....obviously it was not obvious to you....no big deal, but why critic my post? Lets exchange information without sniping.

Using EAN on a safety stop if dive gas was 21% requires another tank with EAN at that stop or a second stage with EAN from a surface platform. My request was what % EAN [or 100% 02] folks on this forum were using at their safety stops. If basic scuba classes now address EAN at safety stops when diving air I missed that.

 

[inquis]

My request was what % EAN [or 100% 02] folks on this forum were using at their safety stops.

I'd guess every single diver on this forum is using their back-gas at their safety stop, so typically 36% or 32%. I believe you're substantially overthinking this, as the nitrogen off-gassing during a 5 minute safety stop after an NDL dive is hardly anything, even with the maximum possible gradient using O2 [ETA: which brings its own set of dangers].

You will gain much greater benefit from diving Nitrox during the entire dive (same bottom time as if you were on air). Not absorbing the gas in the first place is vastly smarter than a poor attempt to get rid of it in the final moments.

 

[Wallowa]

I'd guess every single diver on this forum is using their back-gas at their safety stop, so typically 36% or 32%. I believe you're substantially overthinking this, as the nitrogen off-gassing during a 5 minute safety stop after an NDL dive is hardly anything, even with the maximum possible gradient using O2.

You will gain much greater benefit from diving Nitrox during the entire dive (same bottom time as if you were on air). Not absorbing the gas in the first place is vastly smarter than a poor attempt to get rid of it in the final moments.

Thanks good input and appreciated. I am after any improved reduction of microbubbles/decompression stress; even if very small ['hardly anything'] I want, no need, such a reduction due to previous injuries, age, decades of deep dives and current dive profiles to NDL. Unlike others on this forum who use 36% or 32% 'back-gas' even though EAN certified and having dived it in 80s, I currently only dive 21%.

My dive depths preclude using EAN and getting an EAN fill where I live would involve a 9 hour drive. I have a compressor for 21% fills and no intent or ability to mix my own EAN.

Yes, I concur dive shallower, use EAN as primary/safety stop gas and give a buffer from NDL would be another way to accomplish bubble reduction and possibly elimination. But, other than backing off NDL the other options do not fit why and how I dive.

My proposal to use EAN at safety stop when diving 21% is not a new concept and has been recognized as benefit for a long time. But I do not say or recommend that anyone else do what I plan on doing. You have mentioned other means to accomplish my objective and I do appreciate that perspective and suggestions. Again, let each diver decide how they conduct their dives.

Will add a perspective. You mentioned using EAN on safety stop as a "poor attempt to get rid of it in the final moment"; I understand what you said and meant, but consider that any reduction of tissue or blood nitrogen gradient that is above Pp pressure at surface benefits the diver and reduces the chance of asymptomatic injury. The final moment, surfacing, is the crucial decompression moment.

Thanks again, exchange was helpful for me.

 

[rongoodman]

If I was going to the bother of slinging a separate bottle for the safety stop I’d just fill it with O2.

 

[Wallowa]

If I was going to the bother of slinging a separate bottle for the safety stop I’d just fill it with O2.

Good suggestion. What bottle/valve/reg do you suggest? Thanks....

 

[Wallowa]

You didn't miss it. Scuba classes don't address breathing EAN out of a dedicated bottle at safety stops because the concept is ridiculous.

Come on please quit with the insults and bloviations.

 

[chrisch]

Come on please quit with the insults and bloviations.

I don't think anyone is trying to insult you, it is simply that the use of anything other than back gas on a safety stop is totally unheard of and upon examination seems pointless.

Your goal of reducing the risk of DCI is perfectly valid, however the effectiveness of a very short exposure to a much reduced nitrogen gas is much less that the inconvenience and stress of having to carry that gas and with it a seperate tank and regulator.

If you want to give it a go by all means do so. Firstly the seperate tank will work as a bailout, so you need to match the gas mixture to the maximum planned depth if you wish to gain that benefit. Pure O2 will be best for clearing nitrogen but is useless as a bailout unless the dive is very shallow. EAN 32 or similar is more intelligent but then as pointed out above is a better choice for the whole dive.

For a safety stop only perhaps the best option is a small self contained system like the Spare Air. Anything larger and it seems to me you are loading on more nitrogen by dragging the tank around than your are off gassing on the stop. Hence the pony option is probably counterproductive.

 

[MarkA]

Come on please quit with the insults and bloviations.

New word learnt (bloviations)

Interested to know your safety stop depth. Probably not at the 6m end of the safety stop depth range due to the altitude?

If using a shearwater? What does the GF99 and SurfGF say during the safety stop. Could you simulate using 100% O2 to see what improvements there are?

 

[johndiver999]

Thanks good input and appreciated. I am after any improved reduction of microbubbles/decompression stress; even if very small ['hardly anything'] I want, no need, such a reduction due to previous injuries, age, decades of deep dives and current dive profiles to NDL. Unlike others on this forum who use 36% or 32% 'back-gas' even though EAN certified and having dived it in 80s, I currently only dive 21%.

My dive depths preclude using EAN and getting an EAN fill where I live would involve a 9 hour drive. I have a compressor for 21% fills and no intent or ability to mix my own EAN.

Yes, I concur dive shallower, use EAN as primary/safety stop gas and give a buffer from NDL would be another way to accomplish bubble reduction and possibly elimination. But, other than backing off NDL the other options do not fit why and how I dive.

My proposal to use EAN at safety stop when diving 21% is not a new concept and has been recognized as benefit for a long time. But I do not say or recommend that anyone else do what I plan on doing. You have mentioned other means to accomplish my objective and I do appreciate that perspective and suggestions. Again, let each diver decide how they conduct their dives.

Will add a perspective. You mentioned using EAN on safety stop as a "poor attempt to get rid of it in the final moment"; I understand what you said and meant, but consider that any reduction of tissue or blood nitrogen gradient that is above Pp pressure at surface benefits the diver and reduces the chance of asymptomatic injury. The final moment, surfacing, is the crucial decompression moment.

Thanks again, exchange was helpful for me.

Not much of this makes no sense to me.
How do you fill the pony bottle with nitrox if it is too far away to get nitrox fills?
If you are too deep to dive nitrox then why take nitrox in a pony bottle so deep that it is not usable as a bail out gas?
The dangers of taking the "pony bottle" into lethal depths, seems larger than the potential benefit of decompressing with it on a no-deco dive?
How deep are you diving with no usable redundancy in case you have a problem at depth?

 

[Wallowa]

Not much of this makes no sense to me.
How do you fill the pony bottle with nitrox if it is too far away to get nitrox fills?
If you are too deep to dive nitrox then why take nitrox in a pony bottle so deep that it is not usable as a bail out gas?
The dangers of taking the "pony bottle" into lethal depths, seems larger than the potential benefit of decompressing with it on a no-deco dive?
How deep are you diving with no usable redundancy in case you have a problem at depth?

Folks my posts are based on my diving education, training, experience and profession as a Diving Safety Officer; BUT they are only my views and I do not impose them on others. Each diver should be free to decide how they conduct their dives. Dialogues that exchange information are positive but criticisms are not warranted on another person's choices.

I will try one last time...if you reference Wienke, Bennett, Bove, Gilliam, Mount, Edmonds, Dueker, Barsky, Lippmann, et al, they state the benefit of using a high % of oxygen at safety stops...the 'oxygen window' benefit.....even on dives within the NDL....when a diver surfaces they will have microbubbles/nuclei in the circulatory system....removing or diminishing those 'silent bubbles' reduces the chance of asymptomatic tissue damage...using a high % of oxygen at a safety stop is a standard of practice....even shallow mandatory decompression stops use high % of 02....my use is only at a shallow safety stop....my primary gas is 21% air.

I am NOT going to use EAN as a "bailout bottle" or emergency gas supply....but only at shallow safety stops....no "lethal depths".....the concept of redundancy "at depth" is a joke to me......I dive deep but do it in 1/3s...I have never run out of gas in 69 years of diving, never....this current craze to double up all your gear does not make you safer, judgement and in-water skills makes you safer....I see the "two of everything" as just more failure points and for 'joining the club' since the proliferation of "Tech"....again only my perspectives and how you dive or the gear you use is strictly your business. No judgements on your actions or choices.

Question was asked at what depth when diving at altitude do I make a safety stop. Currently diving at 4,300ft ABSL I make safety stop of 5+mins at 15-17ffw [NOAA]. This is usually a swimming along that depth contour 'stop'. Slow swim and extending stop time when feasible. Another question....I plan to fill a 13cf pony bottle with EAN40 using a whip from a 117HPcf bottle; this will allow many sufficient fills of 13cf before pressure drops in 117 enough that I need to re-fill the 117.

Not sure why so many of these threads end up in persons not just espousing opinions or exchanging information but rather telling others that their choices 'doesn't make sense' or are wrong. Nobody has the keys to the kingdom and is truly a 'know it all'. I certainly am still learning. One size does not fit all; keep an open mind and always entertain that "I might be wrong", I operate from that premise. Out here and I will stay off this thread so as not to generate more negativity.

DSO