Couple questions on a pony bottle for bail out

[kwinter]

I am sure that in theory it is better to ascend on nitrox than air, but what is the MAGNITUDE of the difference when we are talking a non-deco, recreational dive? THAT is the difference I am curious to see.. I don't have the software to do it.

I'm still gonna put mostly air in my pony, but I am curious to see a quantification of the effects of switching the ascent gas from say 32% (at 130 ft) to air for the direct assent. Is the numerical difference really "dangerous"??

After being a blowhard through the entire thread, it seems you have finally gotten the point I was making from the beginning. While it may not be dangerous to switch to air on ascent from a nitrox dive, it is clearly better to stay with nitrox for the whole ride. So it can not be denied that the best gas to have in your pony bottle is nitrox, not air. It avoids any chance of ongassing N2 and putting you into a mandatory deco position, and keeps your NDL the same. The only disadvantage it has is the slight cost difference and inconvenience when it needs to be topped off periodically. Small price to pay for always having a better gas available.



iPhone. iTypo. iApologize.

 

[Greg_Vic_Diver]

You support your contention that the practice is dangerous by repeating that it is dangerous...

You must be a great father... "Because I said so... that's why!!!!"

And you as well: "I'm not sure if this is dangerous because I have no way to figure it out but I'm gonna do it anyways.."

 

[DaleC]

Let's go back to basics for a moment.

On a recreational dive we have several options for tank configuration. These would be:

• Single tank
• Single tank with H valve
• Single tank and pony
• Independent doubles (either backmount or sidemount)
• Manifolded doubles

The first truth is that all of these configurations will work. There is no "wrong" set up. Which one you choose depends on what value you place on their individual features.

A Single tank is the easiest and lightest but offers no redundancy. That is achieved by maintaining good buddy contact. Great if you have a good buddy and are on the same page as far as protocols go; not so great if you have unknown or unreliable buddies or if you dive in conditions where separation is hard to avoid.

A Single tank with H valve offers some redundancy but that is dependent on isolating the offending valve, which may or may not offer enough gas for reserves if not done quickly. You also need a separate H valve on every tank you dive.

A Single with pony offers a completely redundant air source in a small, easy to manage package. It is portable, reliable and easy to use.

Independent doubles allow more gas to be carried while still maintaining a completely redundant airsource. Basic gas management and regulator swapping skills are required and maintaining reserves in both tanks means less gas is available for the dive (than manifolded doubles).

Manifolded doubles allow more gas (like ID's) and a bit more gas to be used on the dive (the portion otherwise reserved in independent doubles). They are heavier, cost more and less portable (than singles/singles/ponies) and require good valve shutdown skills (they only offer true redundancy when one isolates effectively).

So the question becomes: What sort of diving is the recreational diver doing and what features do they want/need?

Some have good buddies they can rely on (with their life) so a single will be good enough. They will argue any additional redundancy is unnecessary.

Some do basic rec profiles but travel and get coupled with insta-buddies, or solo, or just want the reassurance of a second airsource on their person, that they control. In that case a single and pony will suffice. The will argue a light, portable, easy to use system is better than leaving things to chance and better than humping doubles on every dive they do.

Some choose a H valve, which offers redundant regulators but not redundant tanks. Some believe this is enough redundancy (though those divers should choose a large volume tank so they can isolate in time to preserve a meaningful reserve.

Some want to do longer/deeper dives and want more gas so they choose double tanks. Or perhaps they do some tech and some rec diving and don't want to change rigs all the time (the choice between independent and manifolded doubles I'll leave for another debate). They will argue that they are used to doubles, already have them and can use them on all their dives.

One problem in this debate is in which direction the diver is viewing recreational dives requiring redundancy.

The rec diver looks upwards, seeing a need to add a piece of equipment. For many, the most cost effective and adaptable solution is the pony: cheap, easy to use and travel with. There really are no negatives to a ponies use, if matched to the dive. Suggesting manifolded doubles is far beyond their requirements.

A tech diver looks downward, at simpler dives than they are equipped for. They already have doubles and know how to use them, so suggesting them seems reasonable. They don't need to add equipment, just use what they have. They see the positives of doubles use but not the negatives and the lack of need for that much equipment in the recreational realm.

 

[dumpsterDiver]

After being a blowhard through the entire thread, it seems you have finally gotten the point I was making from the beginning. While it may not be dangerous to switch to air on ascent from a nitrox dive, it is clearly better to stay with nitrox for the whole ride. So it can not be denied that the best gas to have in your pony bottle is nitrox, not air. It avoids any chance of ongassing N2 and putting you into a mandatory deco position, and keeps your NDL the same. The only disadvantage it has is the slight cost difference and inconvenience when it needs to be topped off periodically. Small price to pay for always having a better gas available.



iPhone. iTypo. iApologize.

No... I don't concede anything. My goal in diving is NOT to do it in the safest manner possible. I want to have some fun, I want it to not be too hard, I don't want it to be excessively uncomfortable or expensive and I am generally looking for some productivity. I might be in the form of dead fish or lobsters or even video, but I like to bring something back.

If I wanted my diving to be as safe as possible, I would dive 12 feet deep and never spear a fish.

There are many reasons to use air and there is apparently ONE reason to use nitrox. The one reason is that it is theoretically SLIGHTLY better from a nitrogen absorption perspective. I image that with an emergency ascent rate of 40 or 60 feet per minute, the difference in air versus nitrox (for a non-deco dive) is negligible... but I don't have the software.. show me the benefit.. PLEASE.

Also with respect to the other guy's claim of "dangerous". When an intelligent person says that a situation or activity or practice is dangerous, they should have some idea about what constitutes "dangerous". They should have some statistical support, maybe some anecdotal evidence or experience or even be able to clearly describe how a particular scenario could go south and result in significant harm.

When an intelligent person "knows" that a particular activity is less safe than a similar one (or alternate one) then they could be expected to say that Activity A is less safe than Activity B. However this is different than claiming one activity is clearly dangerous without seemingly any meaningful justification. Why not just say: "you're gonna DIE!"

I must be a total retard.. I fill my leaky truck and bicycle tires with nitrox and my pony with air.

 

[kwinter]

I must be a total retard.

We are finally in complete agreement.:cool2:

 

[DaleC]

...I fill my leaky truck and bicycle tires with nitrox and my pony with air...

There's some weird truth there. Divers have been using air successfully since the 1800's yet in the last 10-20 years we have developed a mindset among some that air is only good for filling tires. Now they fill tires with nitrogen and look at you funny if you say you want air. "Are you sure, don't you know the benefits of nitrogen?"

Marketing 101: first create a need and then supply the solution. The best way to create need is to create fear. The most strenuous advocates are not the best informed, they are the most fearful. To argue with the well informed is to disagree with an idea. To argue with the fearful is to deny salvation.

 

[Greg_Vic_Diver]

There are many reasons to use air and there is apparently ONE reason to use nitrox. The one reason is that it is theoretically SLIGHTLY better from a nitrogen absorption perspective. I image that with an emergency ascent rate of 40 or 60 feet per minute, the difference in air versus nitrox (for a non-deco dive) is negligible... but I don't have the software.. show me the benefit.. PLEASE.

Also with respect to the other guy's claim of "dangerous". When an intelligent person says that a situation or activity or practice is dangerous, they should have some idea about what constitutes "dangerous". They should have some statistical support, maybe some anecdotal evidence or experience or even be able to clearly describe how a particular scenario could go south and result in significant harm.

When an intelligent person "knows" that a particular activity is less safe than a similar one (or alternate one) then they could be expected to say that Activity A is less safe than Activity B. However this is different than claiming one activity is clearly dangerous without seemingly any meaningful justification. Why not just say: "you're gonna DIE!"

OK, I'll bite. I'll admit, I could have used a qualifier like "potentially" dangerous, please don't blow it out of proportion.

The main issue was saying that the ascent doesn't matter and and thus one can use whatever gas you want as it doesn't count. It does count and this conversation just shows how convoluted a "pony" setup is along with the lack of training for mixed gas decompression diving (which is essentially what you are now doing). One could argue that doing mixed gas decompression diving without training is less than ideal...it's dangerous

As for a specific example, if you are switching to your "reserve", and your reserve has more inert gas loading than your bottom gas, you need to take that into account when figuring out how much gas to carry in your reserve or else you will could potentially find out really quick if you're claustrophobic or not, spending 6+ hours in a tin can.

Let's walk through this, you run out of gas at the NDL diving 32% nitrox (worst possible time), then switch to air and think this won't add any deco, then ascend extra quickly blowing away some deco (which may or may not cause a problem depending on too many factors to list) , now you are on the surface by yourself (you obviously bailed out and ran for dodge) and may need assistance if you do have some complications and no one is around...sounds like a great day diving :shocked2:

Why take the extra risk? You already have had a major problem that required you to switch to your reserve, why not nip the incident pit in the butt and have the right gas (and enough of it) to safely reach the surface doing all stops and ascending at a slow rate. Or even better, dive a single tank with proper gas planning and a good buddy that you practice with and not have to deal with any of these convoluted issues.

---------- Post added July 22nd, 2014 at 10:12 PM ----------

Let's go back to basics for a moment.

On a recreational dive we have several options for tank configuration. These would be:

• Single tank
• Single tank with H valve
• Single tank and pony
• Independent doubles (either backmount or sidemount)
• Manifolded doubles

The first truth is that all of these configurations will work. There is no "wrong" set up. Which one you choose depends on what value you place on their individual features.

A Single tank is the easiest and lightest but offers no redundancy. That is achieved by maintaining good buddy contact. Great if you have a good buddy and are on the same page as far as protocols go; not so great if you have unknown or unreliable buddies or if you dive in conditions where separation is hard to avoid.

A Single tank with H valve offers some redundancy but that is dependent on isolating the offending valve, which may or may not offer enough gas for reserves if not done quickly. You also need a separate H valve on every tank you dive.

A Single with pony offers a completely redundant air source in a small, easy to manage package. It is portable, reliable and easy to use.

Independent doubles allow more gas to be carried while still maintaining a completely redundant airsource. Basic gas management and regulator swapping skills are required and maintaining reserves in both tanks means less gas is available for the dive (than manifolded doubles).

Manifolded doubles allow more gas (like ID's) and a bit more gas to be used on the dive (the portion otherwise reserved in independent doubles). They are heavier, cost more and less portable (than singles/singles/ponies) and require good valve shutdown skills (they only offer true redundancy when one isolates effectively).

So the question becomes: What sort of diving is the recreational diver doing and what features do they want/need?

Some have good buddies they can rely on (with their life) so a single will be good enough. They will argue any additional redundancy is unnecessary.

Some do basic rec profiles but travel and get coupled with insta-buddies, or solo, or just want the reassurance of a second airsource on their person, that they control. In that case a single and pony will suffice. The will argue a light, portable, easy to use system is better than leaving things to chance and better than humping doubles on every dive they do.

Some choose a H valve, which offers redundant regulators but not redundant tanks. Some believe this is enough redundancy (though those divers should choose a large volume tank so they can isolate in time to preserve a meaningful reserve.

Some want to do longer/deeper dives and want more gas so they choose double tanks. Or perhaps they do some tech and some rec diving and don't want to change rigs all the time (the choice between independent and manifolded doubles I'll leave for another debate). They will argue that they are used to doubles, already have them and can use them on all their dives.

One problem in this debate is in which direction the diver is viewing recreational dives requiring redundancy.

The rec diver looks upwards, seeing a need to add a piece of equipment. For many, the most cost effective and adaptable solution is the pony: cheap, easy to use and travel with. There really are no negatives to a ponies use, if matched to the dive. Suggesting manifolded doubles is far beyond their requirements.

A tech diver looks downward, at simpler dives than they are equipped for. They already have doubles and know how to use them, so suggesting them seems reasonable. They don't need to add equipment, just use what they have. They see the positives of doubles use but not the negatives and the lack of need for that much equipment in the recreational realm.

Nice summary. I take it you are a rec diver then looking upwards then? Just curious, why aren't most rec divers also looking sideways for better buddies/training instead of just adding another piece of equipment? That seems like the easiest answer to me.

 

[leadduck]

<...>

A Single tank is the easiest and lightest but offers no redundancy. That is achieved by maintaining good buddy contact. Great if you have a good buddy and are on the same page as far as protocols go; not so great if you have unknown or unreliable buddies or if you dive in conditions where separation is hard to avoid.

<...>

Some have good buddies they can rely on (with their life) so a single will be good enough. They will argue any additional redundancy is unnecessary.

Some do basic rec profiles but travel and get coupled with insta-buddies, or solo, or just want the reassurance of a second airsource on their person, that they control. In that case a single and pony will suffice. The will argue a light, portable, easy to use system is better than leaving things to chance and better than humping doubles on every dive they do.

<...>

You're implying here that using single tanks is only safe if you can rely with your life on your buddy, and I think that's wrong because your summary is missing one of the main points:

Many do recreational NDL dives in a shallow depth (<60fsw) where a redundant air source is not needed for a safe CESA. They will argue that a redundant air source is unnecessary and not worth the inconvenience of maintaining and carrying it, no matter how unreliable the insta-buddy is.

 

[nimoh]

No... I don't concede anything. My goal in diving is NOT to do it in the safest manner possible. I want to have some fun, I want it to not be too hard, I don't want it to be excessively uncomfortable or expensive and I am generally looking for some productivity. I might be in the form of dead fish or lobsters or even video, but I like to bring something back.

If I wanted my diving to be as safe as possible, I would dive 12 feet deep and never spear a fish.

There are many reasons to use air and there is apparently ONE reason to use nitrox. The one reason is that it is theoretically SLIGHTLY better from a nitrogen absorption perspective. I image that with an emergency ascent rate of 40 or 60 feet per minute, the difference in air versus nitrox (for a non-deco dive) is negligible... but I don't have the software.. show me the benefit.. PLEASE.

Also with respect to the other guy's claim of "dangerous". When an intelligent person says that a situation or activity or practice is dangerous, they should have some idea about what constitutes "dangerous". They should have some statistical support, maybe some anecdotal evidence or experience or even be able to clearly describe how a particular scenario could go south and result in significant harm.

When an intelligent person "knows" that a particular activity is less safe than a similar one (or alternate one) then they could be expected to say that Activity A is less safe than Activity B. However this is different than claiming one activity is clearly dangerous without seemingly any meaningful justification. Why not just say: "you're gonna DIE!"

I must be a total retard.. I fill my leaky truck and bicycle tires with nitrox and my pony with air.

I was a little curious after reading this discussion of using air for ascent, so I ran a scenario through vplanner. I chose a dive profile that is at about the NDL of EAN32, specifically 29 minutes at 100 feet.

- doing this dive completely on 32% and with an ascent rate of 30 ft/min gives a deco stop of 0:20 at 20 feet

- doing this dive and switching to air at 95 feet with an ascent rate of 30 ft/min gives a deco stop of 3:20 at 20 feet

- doing this dive and switching to air at 95 feet with an ascent rate of 60 ft/min gives a deco stop of 2:40 at 20 feet

I wouldn't call that an insignificant difference, but wouldn't really call it dangerous either, if the dive is well planned taking this into consideration. However, personally, if I were putting 32% on my back, I would put 32% in my pony as well, as it makes the planning easier.

 

[DaleC]

The main issue was saying that the ascent doesn't matter and and thus one can use whatever gas you want as it doesn't count. It does count and this conversation just shows how convoluted a "pony" setup is along with the lack of training for mixed gas decompression diving (which is essentially what you are now doing). One could argue that doing mixed gas decompression diving without training is less than ideal...it's dangerous


Nice summary. I take it you are a rec diver then looking upwards then? Just curious, why aren't most rec divers also looking sideways for better buddies/training instead of just adding another piece of equipment? That seems like the easiest answer to me.

Your bias is beginning to show now. You have somehow taken recreational diving with a pony into the arena of mixed gas decompression diving... ? Next you will be telling us we all need to do min deco instead of safety stops.

I'm playing nice but your arrogance is a little hard to ignore. We have been doing this dir vs the world debate for years now and most of your comments have been beaten to death; to the point that I'm actually bored to rebut them. Many of us have come to terms with living and letting live with different regimes and approaches, as long as they suit the conditions, so the latest attempt to descend unto the masses to educate the less fortunate isn't required.

That you choose your regime is fine with me, and you will never hear me arguing it is a wrong choice.. for you; though I may argue against some points (I also argue for many ideas). However, don't try to argue that other choices are wrong. First, because it's insulting. Second, because it's an erroneous stance. And third, because it weakens your own position as being inflexible and dogmatic.

---------- Post added July 23rd, 2014 at 08:06 AM ----------

You're implying here that using single tanks is only safe if you can rely with your life on your buddy, and I think that's wrong because your summary is missing one of the main points:

Many do recreational NDL dives in a shallow depth (<60fsw) where a redundant air source is not needed for a safe CESA. They will argue that a redundant air source is unnecessary and not worth the inconvenience of maintaining and carrying it, no matter how unreliable the insta-buddy is.

Absolutely. I do this myself but I didn't want to muddy the waters any more by offering another point of contention.

---------- Post added July 23rd, 2014 at 08:11 AM ----------

I was a little curious after reading this discussion of using air for ascent, so I ran a scenario through vplanner. I chose a dive profile that is at about the NDL of EAN32, specifically 29 minutes at 100 feet...
...I wouldn't call that an insignificant difference, but wouldn't really call it dangerous either, if the dive is well planned taking this into consideration. However, personally, if I were putting 32% on my back, I would put 32% in my pony as well, as it makes the planning easier.

Yes, but wouldn't the better strategy for a recreational diver be to dive conservatively instead of pushing up against the NDL's and depending on the fractional content of O2 in emergency gas to ward off impending DCS? Deco limits being somewhat theoretical in the first place. When I hear people using their choice of pony gas as an anti DCS strategy I tend to think the horse is already out of the gate.