Sucking straight from the bottle

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kafkaland

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I'm currently learning sidemount, and one of the advantages is that you can do pretty much whatever you want with your tanks. Switching first stages underwater, handing off a tank, or even breath directly from the tank valve, sans first stage. The latter I had a hard time believing, so I tried it earlier tonight in my exercise pool. No regulator, harness or BCD, justmy trusty HP 119 and me. And I was amazed how easy it was. Once I had the gas flow rate right, it was a breeze breathing straight from it and swimming with it. Who needs regulators, anyway? I suck, and I may even be good at it! But seriously, can you imagine any scenario where you would actually have to use this method? Good to know it works, though.
 
bare tank breathing used to be taught in classes but is now discouraged by all of the agencies.

Scenarios are pretty much 0, same as a lights out exit in a cave. It can happen, but the odds of a double first stage failure are pretty minimal
 
Fun party trick but in reality, not really recommended.
 
Like sitting over an engine pouring gas down carb to keep it running when the fuel pump pukes. I've done both but it's not my preferred method of operation for either.



Bob
------------------------------
There is no problem that can't be solved with a liberal application of sex, tequila, money, duct tape, or high explosives, not necessarily in that order.
 
kafkaland,

There is real hazard to breathing right off the tank, and I'm surprised that no one has mentioned it. That is pulmonary barotrauma, or air embolism; taking high pressure air into your mouth directly can fairly easily cause lung over-expansion, and that leads directly to an air embolism, which is potentially life-threatening. This is why no instructional agency advocates breathing directly off the tank. There is only one cell between the capillaries in the lungs and the air itself. This is very easily ruptured by pressure, and the pressure is almost instantly transferred from your mouth to the air sacs in the lungs. This is why we use a reducing regulator to get air at ambient pressure, so that we don't inadvertently expose ourselves to this potentially deadly physical effect of pressurized air.

SeaRat
 
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I pictured it more like breathing off of a free flowing regulator.
 
I pictured it more like breathing off of a free flowing regulator.

That's how it felt like, but easier because of the added control over the flow rate by having the tank valve in my hand. Excess air just bubbled out of my mouth. To risk lung over expansion, I would imagine one would have to clamp down hard with the lips around the valve, and I'm not sure that's even possible.
 
John, not 100% correct on that, the purge button on the regulator can just as easily cause an embolism fwiw, that is why it is a demand valve, and you aren't supposed to use the purge button unless you have to. This is also why most EMS teams don't allow demand valves on the O2 regulators, they usually use MTV100's. In practice this is no different than breathing off of a freeflowing regulator like Keith said
 
John, not 100% correct on that, the purge button on the regulator can just as easily cause an embolism fwiw, that is why it is a demand valve, and you aren't supposed to use the purge button unless you have to. This is also why most EMS teams don't allow demand valves on the O2 regulators, they usually use MTV100's. In practice this is no different than breathing off of a freeflowing regulator like Keith said
Actually, for what it's worth there is a big difference between breathing off a free flowing regulator and breathing off a tank valve directly, as there is a huge difference in starting pressure. That is why they are called "two-stage regulators." The pressure coming off a second stage starts at what? 140 psig? The pressure off a diving cylinder can be between 2000 and 3000 psig. That's more than an order of magnitude difference, and leaves very little room for error.

There is one other difference, and that is that with a second stage, there is always an exhalation valve which vents any air that is over 2 inches or so of water pressure. On a tank valve, if the diver inadvertently places a lip lock on the valve, there is no where for the air to go but into his/her lungs, making an overpressure accident much more likely.

SeaRat
 
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But...but...but...

That's how the guy in the movie Sanctum got out of the cave!

(That's a spoller, I know--I may be the only one who actually watched that movie to the end.)
 
https://www.shearwater.com/products/perdix-ai/

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