Why extra air when solo?

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“A freeflow is just one example, other failures are possible and you don’t want it to be a death sentence.”

Freeflows will happen, usually first stage freeflows, no matter what OC kit is used, expanding gas gets cold and freezes stuff. People do actually die this way, a member of another local club died about three years ago due to a freeflow. It is not if but when.

Really a lot of what we teach people is about redundancy. Initially that comes from a buddy, eventually from kit and a buddy, and then for solo just from kit. I don’t expect kit to fail, it almost never happens, but freeflows are common.

Personally I use Apeks regulators. I think they are excellent and very suitable for deep cold water, however I wouldn’t bet my life on taking just one on a dive.
The highlighted text is true only for single hose regulators, but not for double hose regulators. For decades double hose regulators were the standard for diving in the Antarctic. But they were discontinued by the manufacturers, fell into disrepair, started leaking sea water into the case, and then freezing up, so were discontinued. But double hose regulators have a distinct advantage over single hose regulators, in that both the first and second stages are isolated from the water. The double hose regulator therefore will not freeze up under normal use.

Concerning single hose Regulators and freeze-up, here's an interesting study:
BACKGROUND: Single-hose scuba regulators dived in very cold water have a probability of experiencing first- or second-stage malfunction yielding complete occlusion of air flow or massive free flow that rapidly expends a diver's air supply, both conditions referred to as regulator "freeze-up". Principal factors contributing to ice crystallization in the regulator second stage include manufacturer's design, materials, and quality control, exhalant breath of diver, adiabatic gas expansion, mass flow, time, and temperature. MATERIALS AND METHODS: 11 divers (mean height 180.1 cm, mean weight 84.6 kg) logged a total of 133 dives in -1.86 C sea water under 6-m thick Antarctic fast ice. Dive profiles had an average depth of 38 msw and dive time of 29 min, including a mandatory 3 min safety stop at 6 msw. Twenty-seven commercially available, unmodified regulator units from 9 different manufacturers underwent standardized pre-dive regulator care and were randomly assigned to divers. Depths and times of onset of second-stage regulator free-flow were recorded. RESULTS: In 133 dives, there were 28 free flows. The free flows were not evenly distributed across the regulator brands. The regulators classified for the purpose of the test as "better" suffered only 5 free-flows out of 77 exposures (6% combined incidence), and the others suffered 23 out of 56 exposures (41% free-flow incidence). Testing on three regulators was aborted when free flow incidence reached 50%. Differences between regulator free-flow incidences were tested by the Chi-square test. The pooled incidences for the four best performing regulators were compared to the five remaining regulators. The differences between the groupings was significant at P<0.001. CONCLUSION: Regulator freeze-up is a probabilistic event; even the best regulators can fail under polar conditions. Combined laboratory and field-testing, proper pre-dive regulator care, depth-dependent gas density control, breathing rate, and diver experience can influence freeze-up incidence.
[abstract] SCUBA REGULATOR PERFORMANCE FOR UNDER-ICE SCIENTIFIC DIVING OPERATIONS
I will have more to say later.

SeaRat
 
Ok, I’ll bite. What’s the point of solo diving with a fully redundant gas supply and then putting two second stages on your back gas?

Had a mouthpiece come off. Yes, I could still breath off that. Simpler to just use the other second stage and finish the dive.

The fact that I am diving in a solo configuration does not mean I am actually diving solo. I dive in a solo configuration with most instabuddies. Have had to do a couple of temporary air shares while we sorted out their issues or extended their dives. Pony is a 19 and prefer to leave it alone and full in those cases where it is essential.
 
In addition to being a diver for a very long time, trained by both the U.S. Navy and the USAF, and a diving instructor (NAUI #2710), I have worked in the occupational safety and health, and industrial hygiene, fields for over 30 years before retiring. In the latter career fields, we have what is called a Risk Assessment Matrix, and a Heirarchy of Controls, from a ANZI Z10 Standard for Occupational Safety and Health Management Systems.

We'll talk about the Risk Assessment Matrix first (see below). In the occupational safety and health field, if we have a situation for which the severity is potentially catastrophic, which could lead to death or permanent disability, and the likelihood of occurrence was "Frequent," meaning it was likely to occur repeatedly, it was rated in the "red zone" as "High," and the "Operation was not permissible."

What has been described in the discussion of diving in extremely cold water with a single hose regulator likely to freeze up fits into this "Red Zone" category, and the operation should not be allowed to occur.

In the "Heirarchy of Controls," you will notice that the controls most effective are "Elimination," "Substitution," and "Engineering Controls." The least effective are PPE (Personal Protective Equipment) and "Administrative Controls."

There are differences between different single hose regulators, and some are much more prone to freeze-up than others. This is clearly shown in the International Polar Diving Conference publication. On page 35 of this document there is an article titled:

SCUBA REGULATORS FOR USE IN COLD WATER: THE U.S. NAVY PERSPECTIVE
John R. Clarke
Navy Experimental Diving Unit 321 Bullfinch Road Panama City, FLORIDA 32407-7015 U.S.A.

This article should be consulted about regulators, and their ability to be used in frigid conditions.

I discussed the possibility of using a current double hose regulator instead of a single hose regulator. This is an "engineering control" which is much higher up on the hierarchy of controls. The double hose regulator has both the first stage and second stage sitting in air, and not subjected to the diver's breath (which is very humid). The Argonaut Kraken regulator is the only current double hose regulator being manufactured. I have talked with Kraken divers who've used it under ice in the Mid-West/Canada, and they have not experienced freeze-up with this regulator.

I have dived for over 55 years, and had exactly one freeze-up of my single hose regulator. That occurred in a lake on the Oregon coast with a water temperature of 37 degrees in February (winter here). The regulator was a AMF Voit MR-12II, with the Venturi located external to the regulator in a metal tube going to the mouthpiece. To fix that, I did not get a backup octopus, but rather bought a Sherwood Maximus Blizzard regulator, which has heat retention vanes in the regulator. The above report stated this from the U.S. Navy:
From the above regulator rankings, NEDU recommended three regulators be approved for use in cold water. They were the Poseidon Odin/Jetstream (Clarke and Rainone, 1995a), and two Sherwoods (Clarke and Rainone, 1995b), the Maximus and Blizzard. (At the time of our testing, the Blizzard used a heat sink over the exhaust outlet to carry exhaled heat to the lever support assembly; the Maximus did not.)

Perhaps for that reason, we found that the freeze-up susceptibility of the Blizzard was half that of the Maximus. Subsequent to the release of our 1995 report, we learned that the U.S. Antarctic program was successfully using Sherwood Maximus regulators modified with an added heat retention plate within the second stage regulator box, just as had our Blizzard regulators...

...
2004 Results
Category A: Acceptable for temperatures 29°F with minimal free-flow risk.

- Poseidon Xstream.

Category B: Acceptable for temperatures 29°F with minor free-flow risk. - Apeks TX50
- IDI Seaira Spirit Airtec
- Mares Proton Ice Teflon V32 CWD

Caveats

Ice divers should keep in mind the following caveats to NEDU’s regulator testing results, quoted from Layton et al (2004):
• “Testing the same units with different dive profiles, ventilatory rates, regulator adjustment settings, etc., for needs other than those of the U.S. Navy, can be expected to provide different results.”

• “Even when regulators in the “Not Recommended for U.S. Navy use” category are tested under different conditions to determine their suitability for differing needs, those regulators potentially could exhibit acceptable levels of performance.”
This also is an engineering control (using tested regulators for cold water diving).

Redundant air is great, but redundancy with a compromised regulator design in cold water may not be the answer.

SeaRat
 

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Ok, I’ll bite. What’s the point of solo diving with a fully redundant gas supply and then putting two second stages on your back gas?

Incase you run into some putz that wasn't looking at his gages and is OOO.

"Sure here ya go buddy (not my dive buddy) take my long hose and I'll save your life. You owe me a beer!"
 
Ok, I’ll bite. What’s the point of solo diving with a fully redundant gas supply and then putting two second stages on your back gas?
If I were an occasional solo diver, I'd resent removing my ordinary 2nd and plugging the 1st stage port every time I was solo diving.

Much easier to keep my buddy config and just add the pony when I was solo diving. Plus, of course, keeping my gear consistent.
 
Incase you run into some putz that wasn't looking at his gages and is OOO.

"Sure here ya go buddy (not my dive buddy) take my long hose and I'll save your life. You owe me a beer!"

Why not just give him your pony and ascend? Better to stay away from people like that!
 
Why not just give him your pony and ascend?

Redundant gas doesn't always = pony. I'm one of those sidemount weirdos.
 
Absolutely, but:


I've seen a fair amount of 2nd stage freeflows. I've had a few myself. Nearly all of my clubmates who dive during winter has had one or more. All of them on the surface, nearly all of them after the dive.

I've yet to experience, see, or hear one of my clubmates tell me about, a 1st stage freeflow.

What are we doing wrong up here since our experience is directly opposite to what you're saying?

PS: We agree 100%, though, that it's a very good idea to have a fully redundant gas source if you're diving solo or can't make a direct ascent at any time during the dive

I have had/seen a few. Some caused by deliberately dumping gas for a weight check in fresh water, and one this year which seemed to be caused by overbreathing in deepish cold fresh water. Our club regs are supposedly cold water compatible but I will no longer let people use them in particularly cold water. We are generally not diving with very low air temperature, but shallow inland sites can get really cold, and the deeper ones never warm up at depth, so the stress is different.

The bloke I referred to that died got his freeflow doing a DSMB deployment at 20m odd in a site that goes to about 35m.
 
In benign conditions I will and do solo (true solo) without a redundant air supply. However, I impose my own restrictions of 30 feet, more or less, and decent visibility, no overhead or penetration and no reality based entanglement considerations. If I am on a commercial boat or resort that allows solo certified divers to exercise that option, I comply with their rules and those of SDI. Which means having a fully redundant air supply.

Sure, we can have giant octopus, man eating squids or killer clams grabbing me, or maybe I have to hide from a meg or a renegade shrimp boat snares me in a net. But other than that, I am pretty sure I can work my way free and back to the surface 30 feet or less away. An inch or 30 feet, if I cannot breath, well, that is bad, so one must also be familiar with the area to be dived, the environmental conditions and other factors. Doing something without planning or doing so with planning, two different things.

Yes, I am SDI solo certified.

N
 

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