Do you actually see people diving with pony bottles?

[2airishuman]

Can you share any details? I wasn't aware they could cause problems. I can't think of anything that seems reasonable other than someone using it as a stage to extend a dive and getting bent. What happened?

I've brought them up in other threads. There have been at least two similar fatalities, probably more. The specific accidents are starting to blur together in my head but here's what I remember.

Accident A. A diver using a back-mounted pony cylinder mistakenly started the dive with his (primary) tank valve shut but did not realize his mistake because he inadvertently began the dive on the pony cylinder regulator. Diver was observed performing a standard predive check by breathing the regulator while watching the SPG. During the predive check, the SPG reading appeared normal because the primary regset was charged and shut off before the dive. OOA accident ensued when pony cylinder was exhausted. Diver was unable to reach the primary cylinder valve and did not have a buddy nearby.

Accident B. A diver using a back-mounted pony cylinder completed all usual predive checks and started a dive correctly. At some point during the dive, he lost his primary regulator and performed an arm sweep to locate and retrieve it. The regulator so located was actually the pony cylinder regulator but diver did not realize this. OOA accident ensued when pony cylinder was exhausted. Diver never switched back to the primary reg, reasons unclear due to lack of witnesses, conjecture was that the diver was so convinced that it was his primary air supply that failed that he was trying to switch to the pony and never made an effort to locate and use the primary.

These were fatalities.

The lessons that I have taken from these accidents are:

1. A poorly thought through pony configuration adds risk to the dive. Even smart, experienced divers can conclude that a configuration is safe when it is not.
   
   
2. Slung ponies are inherently safer than backmounted ponies, because identical configurations have been in use a stage bottles by technical divers over the past 20 years, and the risks and configuration tradeoffs are well understood based on their use in millions of actual dives. (As an aside, the only fatality that I'm aware of that was blamed on a stage bottle was an entanglement event involving a stage bottle with all-metal rigging on the lower band that could not be cut loose. This is easy to avoid by using braided cord to attach the stage band to the bolt snap, which is now the standard practice)
   
   
3. When using a backmounted pony, it is vitally important to be able to identify which regulator is connected to the pony cylinder, quickly and reliably, under all reasonably foreseeable dive conditions. (I do not believe hose or regulator color or texture, alone or in combination, are sufficient to identify the reg, because sometimes it's dark and I'm wearing gloves. It is unclear to me what steps the divers in these accidents had taken to make the regulators identifiable, but they were experienced divers who thought they were getting it right)
   
   
4. Clear agency guidance is overdue. PADI, NAUI, SSI, SDI, DAN, etc., should be providing evidence-based, experience-based guidance on how to use these tools since their use has become widespread in the general recreational diving community and the hazards are now known.

Some SB participants (Wookie, DumpsterDiver, CuzzA, rek_diver) use a configuration with an integrated power inflator and a necklaced pony regulator. That seems safe to me. There are also some divers who use a backmounted pony valve-down which makes it much easier to follow the hoses and figure out which reg is which, as well as allowing acccess to the pony tank valve. That seems safe to me, too. But neither of these configurations has the lengthy track record of slung cylinders, so I still see that as the best configuration to use.

 

[2airishuman]

Hang tanks are something I've never seen before. Well, I've seen them in videos on youtube - but I've never seen them in person. Same for hang bars at the safety stop.

Maybe it's a regional thing.

I've seen them used on a deep (100') freshwater dives, and I have one I sometimes deploy when it makes sense.

 

[kelemvor]

I've brought them up in other threads. There have been at least two similar fatalities, probably more. The specific accidents are starting to blur together in my head but here's what I remember.

Accident A. A diver using a back-mounted pony cylinder mistakenly started the dive with his (primary) tank valve shut but did not realize his mistake because he inadvertently began the dive on the pony cylinder regulator. Diver was observed performing a standard predive check by breathing the regulator while watching the SPG. During the predive check, the SPG reading appeared normal because the primary regset was charged and shut off before the dive. OOA accident ensued when pony cylinder was exhausted. Diver was unable to reach the primary cylinder valve and did not have a buddy nearby.

Accident B. A diver using a back-mounted pony cylinder completed all usual predive checks and started a dive correctly. At some point during the dive, he lost his primary regulator and performed an arm sweep to locate and retrieve it. The regulator so located was actually the pony cylinder regulator but diver did not realize this. OOA accident ensued when pony cylinder was exhausted. Diver never switched back to the primary reg, reasons unclear due to lack of witnesses, conjecture was that the diver was so convinced that it was his primary air supply that failed that he was trying to switch to the pony and never made an effort to locate and use the primary.

These were fatalities.

The lessons that I have taken from these accidents are:

1. A poorly thought through pony configuration adds risk to the dive. Even smart, experienced divers can conclude that a configuration is safe when it is not.
   
   
2. Slung ponies are inherently safer than backmounted ponies, because identical configurations have been in use a stage bottles by technical divers over the past 20 years, and the risks and configuration tradeoffs are well understood based on their use in millions of actual dives. (As an aside, the only fatality that I'm aware of that was blamed on a stage bottle was an entanglement event involving a stage bottle with all-metal rigging on the lower band that could not be cut loose. This is easy to avoid by using braided cord to attach the stage band to the bolt snap, which is now the standard practice)
   
   
3. When using a backmounted pony, it is vitally important to be able to identify which regulator is connected to the pony cylinder, quickly and reliably, under all reasonably foreseeable dive conditions. (I do not believe hose or regulator color or texture, alone or in combination, are sufficient to identify the reg, because sometimes it's dark and I'm wearing gloves. It is unclear to me what steps the divers in these accidents had taken to make the regulators identifiable, but they were experienced divers who thought they were getting it right)
   
   
4. Clear agency guidance is overdue. PADI, NAUI, SSI, SDI, DAN, etc., should be providing evidence-based, experience-based guidance on how to use these tools since their use has become widespread in the general recreational diving community and the hazards are now known.

Some SB participants (Wookie, DumpsterDiver, CuzzA, rek_diver) use a configuration with an integrated power inflator and a necklaced pony regulator. That seems safe to me. There are also some divers who use a backmounted pony valve-down which makes it much easier to follow the hoses and figure out which reg is which, as well as allowing acccess to the pony tank valve. That seems safe to me, too. But neither of these configurations has the lengthy track record of slung cylinders, so I still see that as the best configuration to use.

Wow! Thanks for sharing that. I have wanted to backmount my pony but just couldn't bring myself to spend the money on a tiny little mounting bracket. Maybe I'll just give up on the idea altogether. Slinging it isn't all that difficult in the first place.

 

[MXGratefulDiver]

Hang tanks are something I've never seen before. Well, I've seen them in videos on youtube - but I've never seen them in person. Same for hang bars at the safety stop.

Maybe it's a regional thing.

They're not uncommon on those deep "signature" dives like the ones I mentioned ... perhaps because the dive ops are pretty much expecting someone to come back with not enough air to do their safety stop. I've also seen them in use on some of the deeper wall dives in Komodo and Fiji ...

... Bob (Grateful Diver)

 

[Wookie]

I've never seen a liveaboard doing moored dives without a hang bottle/hang regulator/deco bar. We used a hang regulator, as when someone went on it, we could hear the first stage in action and then a DM would kit up and jump to see what the issue was. Or see how far the diver was buried in deco.

 

[Lorenzoid]

I wish I could believe that, but when you've got DM's routinely taking barely certified divers to places like Devil's Throat and the Blue Hole I'm not so sure. I've seen too many people on the DM's tank, or doing their safety stop from a hang tank, to think that an AL80 is an adequate size tank for some of the places that highlight a deeper profile on their signature dive sites.

Newer divers simply don't belong below 100 feet on an AL80, no matter if they do have a c-card that says they're "qualified" to be there ...

... Bob (Grateful Diver)

Ha, Cozumel is exactly the place I had in mind when I mentioned I had seen people who ran low on air being assisted by the DM.

I totally agree that an Al 80 isn't sufficient for sites like those. I don't think ponies are the answer, though.

I would say that sites like Devil's Throat and the Blue Hole are outliers among all the dive sites in the world that receive vacation divers. In view of the more typical vacation-diver dive site, it makes sense to me that the standard vacation-diver tank is an Al 80. Also, I think the dive ops that take barely certified divers to supposedly "advanced" sites (well, at least Devil's Throat) are not the majority. (In four trips to Coz, even the last two diving with Aldora on 120s, I have yet to be taken to Devil's Throat--Coz dive ops seem pretty conscious of who they take to "advanced" sites). And even then, how many serious out-of-air incidents have occurred at these sites out of all the divers who are taken there? I think the "standard kit" of an AL 80 is the right tool for the vast majority of sites. Having ponies for rent just doesn't seem like the answer to me. I would think that a bigger tank, like a 100 or 120, is the better route.

 

[MXGratefulDiver]

Ha, Cozumel is exactly the place I had in mind when I mentioned I had seen people who ran low on air being assisted by the DM.

I totally agree that an Al 80 isn't sufficient for sites like those. I don't think ponies are the answer, though.

I would say that sites like Devil's Throat and the Blue Hole are outliers among all the dive sites in the world that receive vacation divers. In view of the more typical vacation-diver dive site, it makes sense to me that the standard vacation-diver tank is an Al 80. Also, I think the dive ops that take barely certified divers to supposedly "advanced" sites (well, at least Devil's Throat) are not the majority. (In four trips to Coz, even the last two diving with Aldora on 120s, I have yet to be taken to Devil's Throat--Coz dive ops seem pretty conscious of who they take to "advanced" sites). And even then, how many serious out-of-air incidents have occurred at these sites out of all the divers who are taken there? I think the "standard kit" of an AL 80 is the right tool for the vast majority of sites. Having ponies for rent just doesn't seem like the answer to me. I would think that a bigger tank, like a 100 or 120, is the better route.

... and I would agree with that last statement ... I'm a big fan of larger cylinders.

On my very first dive trip after getting OW certified, me and my then-wife went to Belize. We stayed in Ambergris Caye, and the dive op ... even knowing that I had about 30 dives at the time, and Cheng had maybe 12 ... really worked at selling us on the Blue Hole trip. We decided not to go. A similarly experienced couple we were diving with at the time did go. They both ran out of air during the dive. The wife was telling us about it the next day, and thought the experience of breathing off a hang tank was the coolest part of the dive. Apparently the message she got from the DM was that she "did great" ...

... Bob (Grateful Diver)

 

[MaxBottomtime]

I wish I could believe that, but when you've got DM's routinely taking barely certified divers to places like Devil's Throat and the Blue Hole I'm not so sure. I've seen too many people on the DM's tank, or doing their safety stop from a hang tank, to think that an AL80 is an adequate size tank for some of the places that highlight a deeper profile on their signature dive sites.

Newer divers simply don't belong below 100 feet on an AL80, no matter if they do have a c-card that says they're "qualified" to be there ...

... Bob (Grateful Diver)

I have a soft rule that divers should not go any deeper than the cubic feet of their tank. An aluminum 80 doesn't give much bottom time below 80 feet, especially if the divers are swimming to keep up with a DM leading them around a reef.

 

[rek_diver]

I have a soft rule that divers should not go any deeper than the cubic feet of their tank. An aluminum 80 doesn't give much bottom time below 80 feet, especially if the divers are swimming to keep up with a DM leading them around a reef.

That's not a rule I'd follow, nor any of the other 20+ divers that were on the regularly scheduled 3-tank boat dive to 3 different Key Largo wrecks courtesy of Ocean Divers. We did the Spiegel Grove, Duane, and Bibb, at depths up to 120' on AL80s and had some nice dives, with bottom times averaging 20-30 minutes. Of course our average depths were considerably shallower than recreational limits but we certainly exceeded 80' for much of those dives.

 

[MXGratefulDiver]

I taught that same rule of thumb to my OW students when I was instructing ...

... Bob (Grateful Diver)