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What is your average Air Consumption?

Discussion in 'Basic Scuba Discussions' started by Diver0001, Sep 21, 2003.

Choose range for avg air consumption

Poll closed Oct 5, 2003.
  1. 6-10 lpm (0.2-0.35 cf/min)

    7 vote(s)
  2. >10-12 lpm (0.36 - 0.42 cf/m)

    11 vote(s)
  3. >12-14 lpm (0.43 - 0.49 cf/m)

    15 vote(s)
  4. >14-16 lpm (0.50 - 0.57 cf/m)

    22 vote(s)
  5. >16-18 lpm (0.58 - 0.64 cf/m)

    11 vote(s)
  6. >18-20 lpm (0.65 - 0.71 cf/m)

    10 vote(s)
  7. > 20lpm (0.72 or higher)

    7 vote(s)
  1. DeepScuba

    DeepScuba Manta Ray

    Sorry guys, but when the numbers are BS, all you have to do is look for the incorrect data. Depth DOES matter, so in the previous example it is quite erroneous to use 8', espacially after 2.5hrs with which it's probably a 4 or 5 ft AVERAGE.

    Also, even 10 minutes makes a difference. Did he accurately do 2.5 hrs?, and yes I understand he didn't do 77cf either. But the 4 or 5ft will more than offset his cf usage.

    I don't want my next question to get lost, as I'm looking for some input, so I'll post it its own post.

    By the way, the tub thing was a JOKE!!!!!!

    I have more than enough actual diving data to back up my claim that very very few people, unless skip breathing, can have those kind of SAC rates. The data is not accurate. I don't have to tell you that you're wrong, it's more than enough for me to SEE it for myself with real diving experiences, with all kinds of "well dove" divers.

    0.18 C'mon!!!!
  2. DeepScuba

    DeepScuba Manta Ray

    And anyhow, 70cf @ 4.5' for 2.5hrs is still about 0.41 I think.

    Now do it it any calm, open ocean, warm environment. Even then, he probably won't be quite as effective.

    Now, with that data, and REAL diving situation I will go along with.

    I've cleaned pools too, you don't have to scrub that hard!!! I would call that "at rest."

    Anyhow......to my question for you all......
  3. DeepScuba

    DeepScuba Manta Ray

    OK, I video a lot (which adds to SAC rates I might say, but I don't calc my rates when I video) What I am getting at is, I have about 20hrs PLUS of my breathing on tape over a few years.

    Basically I know how I breathe, and so does everyone else. I was watching some raw footage this past week, by World-Class Cave divers (So they say :)) Tehehe, I know their names, so they must be well known enough.

    Anyhow, I listened to about 1/2 hr of the videographers breathing. In fact, it caught my attention more than the video itself, quite odd I thought.

    I don't know if I want to call it skip-breathing,....it's kinda like basketball........

    How slow do you have to dribble before it's called a "travel" type of dillema.

    Slow exhale, HUGE, QUICK inhale,...hold.....hold..pause...pause exhale............start over.

    Hmmmm,...........that's one big pause???? Good for SAC rates, maybe, but good for you?

  4. Diver0001

    Diver0001 Instructor, Scuba

    I think you might be right. Although I'm not going to be the one to prove it :)

    But I will say this. I'm not particularly good on air compared to some of the people I dive with and my typical weekend dives will put me in the 12-14 litre/min range (say .46 to keep it simple). I've had some dives lower than 12 but they were all in the tropics.

    My regular buddy uses a tank that's 80% the capacity of mine and we often have virtually the same pressure coming out. That puts him in the .37 range on his normal dives (yes, he's smaller than I am).

    .18 sounds too low to be true though. I agree with that. Let's put it this way. Someone who breathes .18 is using 5 litres of air per min. Assuming that person breathes every 15 seconds or so thats 4 breaths in a min (slow). Using 5 litres that would mean that she (it was a she, right) is filling her lungs with only 1.25 litres of air per breath. That's about 30% of the normal lung capacity for an adult (which is between 3 and 5 litres) with what is acutally a pretty slow rate of breathing. Given this I would conclude that she was either breathing very shallowly (and slowly) or skip breathing. Maybe this result is achievable but I would take it as a warning sign that you're not employing a good breathing technique.

    Extrapolating on that. I would expect that an average adult (lung capacity around 4 litres) drawing say 65% of a full breath 5 times a min (note: typical tidal volumes are probably on the order of 40% capacity so 65% is a fairly deep breath) would use something like 13 litres per minute (.45 or so) much less than that would indicate to me that your breathing technique is probably edging on the questionable unless you're very small.

  5. Drew Sailbum

    Drew Sailbum Instructor, Scuba

    # of Dives:
    Location: Grand Cayman
    runs me about .35 cuft/min SAC rate.

    And I have been diving with friends that put me to shame. One is a competitive freediver and she has a typical working dive SAC rate of .25 and a relaxed diving (not guiding humpties) rate of .20 easily.

    Those who have met me know that I'm no small guy. Still, I can take an Al72 and guide two dives with 500psi remaining. Of course getting in 400-600 dives per year doesn't hurt.

    DeepScuba, you can believe whatever you like but there are those who have shockingly low SAC rates. It happens.
  6. Diver0001

    Diver0001 Instructor, Scuba

    Freedivers train specifially for breath-hold diving and it would surprise me if your friend was not skip breathing to achieve that result. Anything lower than your normal resting breathing rate seems a little suspicious to me. Wouldn't you agree?

  7. DeepScuba

    DeepScuba Manta Ray

    Trends noted:

    Big guys breathe less.

    You warm climate guys breathe less.

    Thin, supposedly well "aired" (that means good cardio) guys breathe MORE

    Freedivers.......well of COURSE, they speak for themselves, really. And read roturners post, they train to hold their breath, tell me they don't skip........they simply do.like I've said, that's one L-O-N-G pause........dribble, dribble, TRAVEL.......

    Here's one for you Drew.........seriously.

    Come dive with us in Canada. Watch your SAC rate double.

    Exposure suit or not, you will INHALE more :)

    I KNOW I'm right around my entire area, since I HAVE run the numbers for many dives and divers.

    Anyone gonna tell me how to get to 0.18????


    By the way, take a look at my question above. I know guys that dive hundreds of dives a year as well, and they ain't THAT good either. They still calc dives at 0.55-0.60

    Then again, in tougher conditions than the Caymans!

    By tougher I mean, colder and darker, it WILL add up to a higher SAC rate.
  8. rollins

    rollins Angel Fish

    I've done about 50 dives in the St. Lawrence this year. My SAC ranges from (in cu-ft/min) a min. of 0.37, a max of 0.83, an overall average of 0.57 (chart attached).

    I notice that it keeps getting lower - my 5-dive moving average is dropping consistently and is now between 0.40 and 0.50 depending on conditions. The colder and deeper dives always seem to have a higher value.

    I don't think the numbers are "bull****" but there definitely can be a large variance in the figures.
  9. DeepScuba

    DeepScuba Manta Ray

    There ya go, nice chart.

    The "average" seems to be narrowing to 0.50-0.57 in the polls.

    Not bad numbers for ballparks, in juicy warm climates.

    Now about the skip-breathing to lower it........
  10. plsdiver4377

    plsdiver4377 Photographer

    # of Dives: 200 - 499
    Location: The border between Western NC, Upstate SC
    Average dive profile was 25' depth with 1/2 - 1 knot current and mid 80 water temp. AL100 tanks used on most dives. Dive times ranged from 60 - 80 min. Starting Pressure 3100
    Ending Pressure 1000

    SAC @ 70 min. = .52 (this is just an average some higher, some lower)

    My wife was still trouncing me on gas consuption;-0. Hers runs .4 - .5. But mine is getting better:wink:, we did have one dive with an exceptionally hard swim and my SAC averaged .9 for the entire dive :eek: and I would guess it was way over 1.5 for a portion of it.

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