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SAC Rate, What is Normal?

Discussion in 'Basic Scuba' started by pasley, Jul 30, 2004.

What is your SAC Rate? (Average last 3 dives)

Poll closed Aug 6, 2004.
  1. 1.5 or higher

    0 vote(s)
    0.0%
  2. 1.0 to 1.49

    1 vote(s)
    1.4%
  3. 0.7 to 0.99

    13 vote(s)
    18.8%
  4. 0.5 to 0.69

    24 vote(s)
    34.8%
  5. 0.45 to 0.49

    12 vote(s)
    17.4%
  6. 0.4 to 0.44

    12 vote(s)
    17.4%
  7. 0.35 to 0.39

    6 vote(s)
    8.7%
  8. Less than 0.34 (what? You need to breath to dive?)

    1 vote(s)
    1.4%
  1. pasley

    pasley Instructor, Scuba

    # of Dives: 1,000 - 2,499
    Location: Lakewood, CA
    3,136
    227
    Ok, so what is a "normal" SAC rate. What is average?

    Taking your last 3 dives, compute your average SAC.
     
  2. Tx_Jeff

    Tx_Jeff Solo Diver

    # of Dives: I'm a Fish!
    Location: Leander, Texas
    133
    1
  3. sharkbaitDAN

    sharkbaitDAN PADI Pro

    # of Dives: 1,000 - 2,499
    Location: Seattle
    194
    25
    Less than .34 is enough to breath. I have about 25 dives between 0.3 and 0.35. My normal range is 0.35 to 0.45.

    The formula is:

    SCR = (1-P2/P1) x Vf/Aa/Tm

    Where
    P1 = pressure in psi at beginning of test dive
    P2 = pressure in psi at end of test dive
    Vf = actual volume of air in tank in cu. ft.
    Aa = pressure in absolute atmospheres
    Tm = time of dive in minutes

    This is from Scuba Diving Mags site:
    http://www.scubadiving.com/training...d/calculating_scr_(surface_consumption_rate)/
     
  4. Snowbear

    Snowbear NOK ScubaBoard Supporter

    7,059
    3
    Depends on the dive. Hangin' out, pretty low. Lotsa swimmin', burn more gas (but stay warmer :wink:)...
     
  5. Diver0001

    Diver0001 Instructor, Scuba

    0
    58
    I average about .42cfpm/12lpm. Last night's dive was .3 but I was feeling pretty relaxed.

    Also I think Snowbear has a good point. It's good for you to know your SAC with different kinds of activities.

    R..
     
  6. Charlie99

    Charlie99 Solo Diver

    # of Dives: 500 - 999
    Location: Silicon Valley, CA / New Bedford, MA / Kihei, Maui
    7,966
    162
    Virtually all my dives are between 0.4 and 0.45cfm. Warm clear water leisurely sightseeing dives. This is definitely towards the low end of the scale.

    It was 0.75cfm before 50 dives. About 0.6cfm around dive 75. 0.5cfm after dive #130, gradually going down to a very repeatable 0.4 to 0.43cfm around dive #200.

    Right now, my SAC is about 0.35cfm in a no motion drift, about 0.5cfm at a transit speed of 1kt (100'/minute), and 0.6 or 0.7cfm while swimming hard. Aerobic fitness level mostly affects how fast my air consumption goes up with increasing workload. If I'm out of shape, then swimming hard requires a lot more air.
     
    gfaith likes this.
  7. SDAnderson

    SDAnderson Dive Charter

    # of Dives:
    Location: On a good day, Lake Michigan
    3,305
    78
    In addition to aerobic conditioning and stress levels, there are a number of less easily controlled factors that greatly influence this number: workloads, body mass and water temps.

    Perhaps the biggest thing influencing SAC rates as reported by most folks is the bul**hit factor, however. Like stories about golf and fishing, never trust someone who volunteers to talk about their gas consumption. :wink:
     
  8. Drew Sailbum

    Drew Sailbum Instructor, Scuba

    # of Dives:
    Location: Grand Cayman
    2,188
    103
    Varies according to workload, but my typical working dive SAC rate is 0.35cuft/min.
     
  9. Mako Mark

    Mako Mark Dive Charter

    3,914
    26
    It varies a lot with physical condition and health. I have noticed recently I am run down, stressed out and have a persistant upper respiritory infection, this has significantly increased my sac rate.
     
  10. Scuba_Steve

    Scuba_Steve Instructor, Scuba

    1,580
    0
    I agree with Reefraff, RE: the biggest factor :)

    Besides, I don't think the above formula (That I saw) takes into account the descent and ascent plus S/S @ 15ft. As we all know, if you take your TRT as "Bottom Time" and use the Max Depth as the constant, you're not very accurate with the math. (Unless the "Test Dive" is "part" of a dive, meaning the Depth IS constant, and the time accurate)> But then, you're concentrating on the numbers then, "to get a good score".

    Then again, we're not all diving Caymans either....
     

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