Sucking straight from the bottle

[John C. Ratliff]

Q1) What pressure is the gas at once it leaves the tank directly by way of the valve?

Depends...upon what it is opening into. The gas will expand from it's tank pressure to ambient, BUT (big BUT) not if there is another "container" for it to expand into." Put a lip lock on the valve the way you do a regulator and you can get the full tank pressure. Use the cupped hand method that Dr. Sam described below, and it will be ambient.

Q2) What pressure is the gas at once it leaves the tank by way of a first and then second stage regulator?

About two inches over ambient is the greatest it will be inside the regulator, because of the exhaust valve acting as an overpressure relief valve (in the event of a malfunction and free flow).

Dr. Sam Miller described the Scripps Institution of Oceanography using the tank breathing technique as an exercise. But what a lot of people don't realize is that university courses in scuba routinely were either on a quarter or semester basis, and were a 3-hour course (3 hours per week for the entire quarter or semester). This course therefore was hugely longer than current scuba courses, which are at the extreme of minimum to become competent in the water. I helped teach Midge Cramer's Oregon State University course in the mid-1970s, and he took the whole class to Hawaii during Spring Break.

SeaRat

 

[boulderjohn]

But what a lot of people don't realize is that university courses in scuba routinely were either on a quarter or semester basis, and were a 3-hour course (3 hours per week for the entire quarter or semester). This course therefore was hugely longer than current scuba courses, which are at the extreme of minimum to become competent in the water. I helped teach Midge Cramer's Oregon State University course in the mid-1970s, and he took the whole class to Hawaii during Spring Break.

This has been raised a number of times to people who keep repeating how much longer and better the courses were. If you are taking a course as a part of your regular school semester, then it can be months long without a problem, and the cost is irrelevant, since you would have paid the same amount of money to the university to take another class anyway. You really can't do that outside of a college environment.

 

[EFX]

Q1) What pressure is the gas at once it leaves the tank directly by way of the valve?

Q2) What pressure is the gas at once it leaves the tank by way of a first and then second stage regulator?

In another age when I did my NASDS Basic cert we had to breath from a tank (no 1st stage) at the bottom of the pool. We sucked air from the air stream. As I recall this was similar to breathing from a free flowing reg. JCR is absolutely right. Clamping your lips over the tank valve is a sure-fire ticket to the ER. The reason that free flow breathing is safe is the average air pressure of the air stream is at ambient pressure, i.e. the same pressure your 2nd stage delivers. Q2: 1st stage output is fixed at anywhere from 110 to 140 psi above ambient depending on reg brand. 2nd stage output is at ambient pressure.

 

[Rich Keller]

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.

I was trained on how to do that and it is easy but you will have a hard time convincing most divers of that. I dive alone most of the time so if my first stage fails I can breath without a reg if needed but I usually dive shallow when I dive alone so it is easier to just get back to the surface instead.

 

[descent]

We used to call it slurping.

Our older instructors sometimes forgot they were talking to the new wave of kids and fell back to calling it sipping.

I have no idea what the new kids are calling it now.

They did teach us the technique of directing the bubbles with the free hand. I didn't feel the hand was necessary, and later taught both hand-directed and hands-free. The air always goes up. Just arrange to be above it, with your mouth open.

I have a hard time imagining someone getting a pulmonary overinflation injury from slurping directly from the tank valve. Human cheeks and lips are just too soft and flappy to make a good, pressure-tight seal.

It is, however, embarrassingly easy to hurt yourself doing this.

I was demonstrating slurping in the shallow end of a pool, and learned that if you release too much air while getting right on top of the orifice, the jet of high pressure air can easily cut through the delicate skin just inside your lip.

Just slow down, back off an inch or so, twist the valve knob conservatively, and you should be fine.

 

[KeithG]

unfortunately compressed air is dangerous. i was taught this at a very young age in shop class. compressed air can easily penetrate the skin. if it also gets injected into your blood stream, then very bad things happen.

https://www.diversalertnetwork.org/diving-incidents/high-pressure-gas-injection-injury#.VFrflWt5mSM

so trying to slurp directly from a high pressure tank can only be labelled as irresponsible or stupid.

 

[John C. Ratliff]

I have looked through my library, and cannot find a reference in any of these diving books to breathing off a bare cylinder! Those who are advocating this as "safe" need to modify that by stating that with a technique, one which is not documented in an reference I've found, it can be done safely. I have looked in the U.S. Navy Diving Manuals (1970 and Rev. 6, 2008), my NAUI instruction manuals, the NOAA Diving Manual--1975, the book, Advanced Diving Technology and Techniques (a NAUI publication, 1989), The British Sub Aqua Club Diving Manual--1972, the Jeppesen Sport Diver Manual, third edition (1978), The New Science of Skin and Scuba Diving, Third Revised Edition, 1968, Al Pierce's SCUBA Life Saving, 1985, Joe Strykowski's Diving For Fun, and Christopher Dueker's Medical Aspects of Sport Diving, 1970, and none of these discuss breathing off a bare cylinder. I've gone through the LA County dive course (1963), the U.S. Navy School for Underwater Swimmers (1967), the NAUI ITC (1973), and USAF Pararescue training, and nowhere have I seen this advocated as a technique in writing or used in training (and I conducted some of the Pararescue training in diving for our squadron).

So here's my challenge to you who are using and/or advocating this as a legitimate training exercise: give me one published reference to this as a training technique. It can be from any era, from the development of self-contained scuba to today, but give me a reference to using this technique. And if you cannot find one, tell me why you would use this in a training situation. Don't tell me about a movie showing it; the movie Thunderball also showed James Bond biting a tube in his teeth to chemically extract oxygen from sea water--but that didn't exist either.

SeaRat

PS:

...I have a hard time imagining someone getting a pulmonary overinflation injury from slurping directly from the tank valve. Human cheeks and lips are just too soft and flappy to make a good, pressure-tight seal...

Actually, we need to make such a seal in order to deliver mouth-to-mouth artificial respiration, or inflate my dive float. It is fairly easy to make such a seal. I agree with giffenk, this is a potentially hazardous undertaking.

PS2: This has already been debated here in 2012:
http://www.scubaboard.com/forums/archive/index.php/t-425892.html

PS3: Here's another thread on this topic from 2007:
http://www.scubaboard.com/forums/archive/index.php/t-201367.html

John C. Ratliff, CSP, CIH, MSPH
NAUI #2710 (retired)
(CSP = Certified Safety Professional, CIH = Certified Industrial Hygienist)

 

[victorzamora]

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.

So, the benefit of sidemount is such that you NEVER have to do that. If my deco reg dies, I'm pulling a the reg off of one of my mains and switching it over. It wouldn't be any fun to have to bare-bottle-breathe for any reason other than to say you've done it.

 

[decompression]

I cringe every time this is mentioned.....and breathing off the inflator..........popcorn.


Sent from my iPad using Tapatalk

 

[EFX]

So here's my challenge to you who are using and/or advocating this as a legitimate training exercise: give me one published reference to this as a training technique. It can be from any era, from the development of self-contained scuba to today, but give me a reference to using this technique. And if you cannot find one, tell me why you would use this in a training situation. Don't tell me about a movie showing it; the movie Thunderball also showed James Bond biting a tube in his teeth to chemically extract oxygen from sea water--but that didn't exist either.

It was back in 1974 that I did the tank breathing. I don't have any of the written materials and I can't remember what the reason was for doing it. At that time equipment wasn't as reliable and buddy breathing from a single reg was the norm. Given the higher frequency of failures breathing off a tank was necessary if your buddy wasn't close enough to help. Then after the lungs are full a CESA could be made. Today, with more reliable equipment and backup 2nd stages to ease sharing air, the chance of a 1st stage failure and having no buddy to help are remote. For solo divers who dive with alternate air sources the necessity of this technique is even more remote. The only scenario I can envision is a diver very low on air, lost within a wreck who is passed a full cylinder through an opening. Breathing directly off the tank he can gain time to switch his equipment over to the full tank. What I do remember doing for my scuba review is breathing off a free flowing reg. Breathing off a free flowing tank is the same except you need to open the valve just enough to get a good stream (not full open). I don't advocate this as a training exercise for rec divers but for tech diving in overhead environments it can be another survival tool.