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running out of air

Discussion in 'Basic Scuba Discussions' started by jonhall, Oct 13, 2015.

  1. BCSGratefulDiver

    BCSGratefulDiver Mental toss flycoon ScubaBoard Supporter

    # of Dives: 2,500 - 4,999
    Location: On the Fun Side of Trump's Wall
    Not everyone teaches that way ... I train my students to consider, before they ever get in the water, how much air they'll need for the dive they're planning to do. If they have even a rough idea, then the chances of running out of air are significantly reduced because they've made bringing adequate gas a part of their dive plan.


    As in many aspects of diving, being proactive will generally produce better results than being reactive ...

    ... Bob (Grateful Diver)
    Doppler likes this.
  2. flots am

    flots am Solo Diver

    # of Dives: I just don't log dives
    Location: Wherever you go in life, that's where you are.
    The only indication you can count on is that your last breath was "your last breath."

    A good, modern reg will breathe perfectly fine right until it stops.

    This might be because you breathed the tank down, which is 100% preventable by monitoring your air supply.

    However it might also be because your tank has crap in it and the tip tube is missing/fell out, you went head down to look under something and the tank valve clogged. This give zero warning, and happens now and then.

    You always need to be prepared that you won't get a "next breath" and have a workable plan. This could be switching to a redundant cylinder & reg, sharing with another diver or doing an Out of Air Ascent.

    However whatever you do needs to be well practised and easily workable with little stress.

    Doppler likes this.
  3. boulderjohn

    boulderjohn Technical Instructor ScubaBoard Supporter

    # of Dives: 1,000 - 2,499
    Location: Boulder, CO
    This sort of planning, too much neglected in the old PADI OW curriculum, is now part of it.
    Doppler likes this.
  4. Eric Sedletzky

    Eric Sedletzky Great White

    # of Dives: 500 - 999
    Location: Santa Rosa, CA
    Yes it was drilled into me, but I guess the difference was for me is that it stuck, and not only did it stick but I became almost OCD about it.
    To me it's just as automatic as looking at my gas gauge in my car, and I can say I've never run OOG driving either. Just like I wouldn't go driving 250 miles out one way into the middle of the desert knowing that I can only get 300 miles out of a full tank of gas. Gas planning on scuba is no different.
    Another person could have had the exact speech from the exact same instructor in the same class and might be a chronic OOA person that has focus problems or is easily distracted by nature or whatever. The point is, the student personalities and character traits have just as much to do with how they were trained as far as the finished product. Not all blame can be put on crappy instruction when there are also crappy students. Running OOG is one of the easiest things to avoid, just pay attention. We're not talking about hoses blowing, regs freeflowing, crap inside a tank blocking the filter, the earth opening up and swallowing you whole, or some other unforeseen massive gear failure or natural disaster, we're talking about simply running OOG.
    macado likes this.
  5. phoenix31tt

    phoenix31tt DIR Practitioner

    # of Dives: 100 - 199
    Location: Trinidad and Tobago
    Well said however we do not often know how far a tank of air will get us... But... Checking our gauge often is at least an easy thing to do... And under regular use, does not drop drastically...

    Your point about being good students and just sensible people in general makes for better divers...

    Last week I swam against a heavy current to get close to a large grouper (my first time seeing one that big)... Frog kicking certainly couldn't cut it so I fluttered... In OMS slipstreams... Sure I got to the subject and was able to hold my own against the current but I knew I was breathing heavily just to do it... Before I went off I checked my gas to make sure I had alot... After I finished and allowed the current to drift me back first thing I did was check my gas again because I know I was breathing heavily... That's not been thaught in a class but it's just the sensible thing to do

    Sent from my iPhone using Tapatalk
    Eric Sedletzky likes this.
  6. Eric Sedletzky

    Eric Sedletzky Great White

    # of Dives: 500 - 999
    Location: Santa Rosa, CA
    OK, how about the question of "How long will 80 CF of Air last me at 60'?
    The answer depends on how hard are you working and how much air do you use on average. Every person is different.
    Finding out how many miles you get out of a tank of gas is a little easier. Every odometer has a reset button that you can zero out the short term mileage counter. Fill your tank, reset the counter to zero, and drive. When the red low fuel light comes on look to see how many miles you accumulated. Try this for city stop and go, for working (hauling stuff, up hills, etc), and on flat freeway during a road trip. This will give you some perspective of what kind of real mileage you get and under what conditions. If you want to take it a step further do it with regular gas and with premium. The results will surprise you.
    Diving is the same. Anybody serious about diving should start to think about and take some interest in their air usage under many different scenarios. That will give you an idea about tank size needed for your personal usage and what type of diving (depths and times) you plan to do.
    phoenix31tt likes this.
  7. dumpsterDiver

    dumpsterDiver Banned

    # of Dives: 2,500 - 4,999
    A good, modern reg will breathe perfectly fine right until it stops.

    Possibly all my regulators do not meet your criteria of "good and modern", but I think your statement is impossible to be factual. The reason being, as the pressure drops, the tank valve itself is going to limit flow. The regulator can not deliver air faster than the valve can supply and as the pressure drops to very low values, the diver WILL be able to detect an increase in breathing resistance.

    In a previous post I went to considerable detail to explain that this is much easier to detect when you are inhaling hard, but a full size tank does not go MT in one second...

  8. lowviz

    lowviz Solo Diver ScubaBoard Supporter

    # of Dives: 200 - 499
    Location: Northern Delaware or the New Jersey Turnpike
    DD, you walked into the middle of an "intervention". Nobody who posted in this thread ever came close to even suggesting that proper gas management was anything other than the one thing that a diver has to do perfectly every time.

    Some of us, myself included, attempted to answer the OP:
    The problem is, this discussion doesn't belong in "Basics". For similar reasons, I was opposed to opening up "Solo" to public view. It is what it is. I find it interesting that instructors (who know better) appear to be forced to defend a position that is refuted by physical reality. We are talking about a few breaths, here.

    This discussion is entirely academic and has nothing at all to do with the skill and art of diving. Again, nobody dives this way.
  9. uncfnp

    uncfnp Solo Diver

    # of Dives: 500 - 999
    Location: North Carolina
    I think its a worthwhile discussion and if some are uncomfortable with it in basic perhaps the op can request a move to advanced.
    lowviz likes this.
  10. Eric Sedletzky

    Eric Sedletzky Great White

    # of Dives: 500 - 999
    Location: Santa Rosa, CA
    One thing I wanted to add is that running out of air on a small pony or on something much bigger like mega tank or a set of doubles are much different. A small pony doesn't have enough internal volume to give you much of anything at say 50 psi. A very large tank like a 130 will have enough internal volume to give you quite a few breaths at 50 psi.
    The bigger the tank volume the slower and more gradual the draw down.
    george_austin likes this.

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