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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)
    8.4%
  2. >10-12 lpm (0.36 - 0.42 cf/m)

    11 vote(s)
    13.3%
  3. >12-14 lpm (0.43 - 0.49 cf/m)

    15 vote(s)
    18.1%
  4. >14-16 lpm (0.50 - 0.57 cf/m)

    22 vote(s)
    26.5%
  5. >16-18 lpm (0.58 - 0.64 cf/m)

    11 vote(s)
    13.3%
  6. >18-20 lpm (0.65 - 0.71 cf/m)

    10 vote(s)
    12.0%
  7. > 20lpm (0.72 or higher)

    7 vote(s)
    8.4%
  1. Texass

    Texass Manta Ray

    678
    0
    16
    That doesn't make it impossible.

    I confess to total dive computer brain rot for figuring my own SAC (thank you Suunto Dive Mgr) Looking at my last 30 dives I have a high of 0.41 and a low of 0.25. Most of the dives are in the 0.28 - 0.33 range.

    I can think of at least 3 people I would choose as dive buddies if having redundant gas available was an issue. My son, who has less than 10 dives under his belt, only uses about 350psi more than I do on a 60 minute dive. That's based on 4 dives we did ranging from 62 to 74 minutes. I wonder what his SAC rate will be in a couple of years.

    Just a BTW; when I find myself immersed in mammaries, the usual response is for my SAC rate to skyrocket!
     
  2. String

    String Master Instructor

    # of Dives: I just don't log dives
    Location: Grand Cayman
    8,504
    358
    83
    SAC varies wildly depending on the type of dive and conditions i do.

    A nice moderate drift dive wont use anywhere near as much air as a wreck dive with some penetration.

    A dive where you have currents you dont want to drift with will use more.

    A dive where im carrying more equipment than usual or trying to perform an unusual task i'll use more etc.

    My SAC varies from 14 - 20 SLM but can jump higher in rare circumstances.

    Id go with the above that temperature makes a HUGE difference. I normally dive dry in water ranging from 6c - 17c depending on the time of year. Even though im warm in my suit, the face still gets cold and you still lose heat through your head despite the hood. Fingers also radiate heat despite gloves.

    Short of sealing ALL your skin off from cold water theres nothing to avoid this.

    In the UK i tend to manage about an hour out of a 15l cylinder before hitting 50 bar reserve but dives abroad in 27c water on a similar depth and profile i manage the same time out of a 12l cylinder. The fact im wearing slightly less weight (8kg not 12) and have less equipment makes some difference but not THAT much.

    Last time i tried working it out my air consumption in warm water was roughly 25% lower than my normal.
     
  3. drbill

    drbill The Lorax for the Kelp Forest Scuba Legend

    # of Dives: 2,500 - 4,999
    Location: Santa Catalina Island, CA
    22,362
    5,191
    113
    Either I'm wrong or the rest of the world is. Must admit to having lost every brain cell I ever owned back in the days I got certified. When I see people reporting figures of 0.3 cu. ft./min I have to ask...

    I start with a 3200 psi cold fill in a HP120 cu. ft. tank. I end my dive after 2 hr 21 min at 500 psi. Therefore I used 2700 psi out of a tank which, if cold filled to capacity, would be 120 cu. ft at 3500 psi.

    (2700/3500) * 120 cu. ft. = 92.6 cu. ft. of air used

    (92.6 cu. ft)/141 min = 0.66 cu. ft./min

    Since my numbers are way off those of the others in this thread, please enlighten this Alzheimer-addled Old Timer so I can calculate my true rate and see how I compare with you air sippers.

    Thanks... and feel free to flame away but I did teach math (up to calculus) in my youth. Back when I was certified we essentially had only one sized tank and no SPG's to measure our consumption.

    Dr. Bill
     
  4. Scuba_Vixen

    Scuba_Vixen Solo Diver

    346
    0
    0
    that's your average for the dive, but you need to divide by the ata for the average depth of the dive to get you sac....

    SAC = Surface Air Consumption

    You were having a blonde moment, I have them 24/7,


    Darlene
     
  5. drbill

    drbill The Lorax for the Kelp Forest Scuba Legend

    # of Dives: 2,500 - 4,999
    Location: Santa Catalina Island, CA
    22,362
    5,191
    113
    My calculations need to be adjusted for depth/pressure. So if I were at 33 ft for the entire 141 min., my rate would be approximately

    0.66 cfm/2.0 atm = 0.33 cfm

    Now that's more like it. Of course I was actually at 100 ft the entire 141 min so... or was it a max depth of 100 ft on a multi-level dive? Oh, oh... I feel the Alzheimers creeping in again.

    Now why didn't they teach that back in the 60's?

    Dr. Bill
     
  6. PhotoTJ

    PhotoTJ Solo Diver

    # of Dives: 0 - 24
    Location: Malibu, CA is where I spend most of my dive time.
    3,311
    8
    38
    Purely for the sake of goofing off, (ie, serving no purpose whatsoever), I got 2 hours and 20 minutes off an aluminum 80. Which is something like .218, I think.

    I was swimming laps in 15' ft of water, loafing.

    If I'm actually diving? (Prying scallops off a rock, chasing lobsters, swimming through surge.)

    Uh, again, I think it's...
    hell, I'm not sure, I'm lousy at math, 67 cf in 60 minutes at 25 feet or so. .644, I think?
     
  7. drbill

    drbill The Lorax for the Kelp Forest Scuba Legend

    # of Dives: 2,500 - 4,999
    Location: Santa Catalina Island, CA
    22,362
    5,191
    113
    PhotoTJ- I'd guess your rate went through the roof when you saw that great white shark off Malibu! Say 5 cfm.

    Dr. Bill
     
  8. PhotoTJ

    PhotoTJ Solo Diver

    # of Dives: 0 - 24
    Location: Malibu, CA is where I spend most of my dive time.
    3,311
    8
    38
    Naw, it never went above 4.8! :wacko:
     
  9. Diver0001

    Diver0001 Instructor, Scuba

    0
    9
    0
    Depth, Bill. What was your depth?

    You still need to "bring it to the surface" by dividing the .66 by the ATA at the depth you made your dive.

    For example. If you dove at 33ft that's 2ATA and your SAC is .66/2

    HTH

    R..

    <Edit: damn. should have read the other posts before repsonding. Post is redundant, sorry>
     
  10. Diver0001

    Diver0001 Instructor, Scuba

    0
    9
    0
    Mine would have gone to zero aftre the heart attack !

    R..
     

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