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3 or 5 minute Safety Stop?

Discussion in 'Basic Scuba' started by tracydr, Jul 5, 2013.

  1. GrumpyOldGuy

    GrumpyOldGuy Solo Diver

    # of Dives: 200 - 499
    Location: West Texas/NH/CA
    4,579
    2,444
    BINGO, WE HAVE A WINNER!

    I never understand people who rush to finish a dive. You paid for the dive so you might was well stretch it out until you run low on gas or hit the dive boat window. I am constantly amazed about the different view at 15' under the boat rather than being 3' off the reef. Everything from seals to reef fish looking for a handout from the boat. Even shore diving, there is an amazing amount of sea life in the top 15'. Its like "free" dive time or a friend offering to but you a beer, why turn it down.
     
    paulw and Kharon like this.
  2. RJP

    RJP Scuba Media & Publications

    # of Dives: 1,000 - 2,499
    Location: New Jersey
    13,460
    6,057
    Depends on the computer. The Vytec DS (DS=Deep Stop) can be set for deep stops or no deep stops. Mine does NOT continue to rack up deco when set for deep stops.
     
  3. supergaijin

    supergaijin Dive Shop

    2,060
    965
    Nothing wrong there as you're not 'deep' at 30'. A dive to 4ata for example to 'no deco limit', then trying to eke out every minute of 'no deco' on ascent is thought by some to be riskier than a dive to the same depth, and then a fairly brisk ascent to around 2ata, then a longer spell there before ascending for a safety stop.

    That said, the vast majority of computers are conservative. Divers don't drop like flies from 'riding the computer'. Plenty of these kind of multi-level dives are made every day without incident. At the same time, all recreational agencies tell you to dive conservatively and not dive to the deco limits.

    IMO it is safer to dive to the 4ata 'limit' and then ascend relatively shallow, compared to diving to the 4ata limit, ascending and diving to the 3.5ata limit, then the 3ata limit etc. The modern dive computer calculates for this. Many divers do not have the gas required to do this profile anyway, but a small point can be made about different profiles and assumed risk. At least one study has shown that very slow ascents increase 'silent bubbles' compared to a faster ascent to the safety stop.
     
    Kharon likes this.
  4. uncfnp

    uncfnp Solo Diver ScubaBoard Supporter

    # of Dives: 500 - 999
    Location: North Carolina
    6,712
    5,546
    I don't own one, I have an Oceanic, but I have been looking at the Sunnto for its conservatism and the deep stop option. I know most of the newest models (not the Zoop) offer it but don't recall the exact models, D6, D9 and Vyper I believe. They call it the Deep Stop RBGM algorithm. I have been unable to find out how it is incorporated into recreational dives and if it changes the SS.

     
    Grocio likes this.
  5. Paulmal

    Paulmal Divemaster Candidate

    # of Dives: 100 - 199
    Location: St. Augustine, Fl
    267
    30
    Most of the divers I do deco dives with add a couple extra minutes of O2, after we clear our last stop. I see no harm in doing similar on a rec dive.
     
  6. The Chairman

    The Chairman Chairman of the Board Staff Member

    # of Dives: I just don't log dives
    Location: Cave Country!
    62,363
    30,959
    I was listening to a DAN presentation at the History of Diving Museum (MM 83, Bayside), and the one thing that stuck out to me, was they could accurately depict what kind of diver you are depending on the type of DCS hit you got. If you got a type I, then you were a commercial diver. If you got a type II (neurological hit) then you were a recreational diver. Now, getting bent is pretty rare. So much so, that the presenter referred to it as slightly above statistical noise. But if you do get DCS, then they can categorize your diving with like a 98% accuracy. That's a wow in my book.

    Later on in his presentation, he casually brought up that the half time for neural fluid was about the same for blood, @ 5 minutes. Now, if you think about it, it only takes about five half times to approach saturation (98.4%). Do the math and that's only about 25 minutes at depth to bring your neural fluids to 98.4% of being saturated at that depth. Doing a five minute half stop will reduce that excess by 50%. That only makes sense to me, so I just do a five minute safety stop. IOW, I'm going to ameliorate the already low percentage of getting bent by addressing the way I'm probably going to get bent in the unlikely event that I do. :D

    BTW, the people who always seem to be overly tired after their dive, never seem to have done a deep stop or a full five minutes at their safety stop.
     
    beanojones likes this.
  7. denisegg

    denisegg Indescribable! ScubaBoard Supporter

    # of Dives: 500 - 999
    Location: South Alabama
    10,066
    524
    Ok...so...a lot of divers don't have 02 as an option as deco divers do (unless they wind up on the boat with it) We can argue for days..but the more you learn..study all the books about air, gas mixes, trimix, algorithms, the less you know (or at least that is the way I felt). When I took advanced nitrox/deco..you realize you are in a world all your own. And ultimately, who decides the fate?
     
  8. vladimir

    vladimir Solo Diver

    # of Dives: I just don't log dives
    Location:
    38,593
    49,782
    The Suunto D9 first came out in 2004, if I recall correctly. I have had mine for over 8 years and it has the option to use deep stops.

     
  9. Atom

    Atom Solo Diver

    # of Dives: 500 - 999
    Location: Montreal
    266
    20
    This depends on the model. And I'm reasonably sure all the new models don't do that anymore.

    I have a Vyper Air and even though it is conservative, if you send it into deco it can clear while you're ascending if your ascent is slow and you only have a few minutes. It also has deep stops (optional), but I'm not convinced it does anything more than show you a timer at the stop depth, it also doesn't seem to mind at all if you blow through the deep stop.

    I certainly wouldn't use it as a deco computer, but on the new models if it goes into deco, don't freak out, just start a slow ascent and most likely it'll clear before you reach the ceiling it shows you. Then take some time to think about how you got into that situation (not monitoring your remaining bottom time) and how to avoid the problem on your next dives. :)
     
  10. lowviz

    lowviz Solo Diver ScubaBoard Supporter

    # of Dives: 200 - 499
    Location: Northern Delaware or the New Jersey Turnpike
    7,401
    4,370
    The RGBM algorithm is a computational nightmare. This http://www.scuba-doc.com/rgbmim.pdf is one of the more readable documents that comes close to answering (in words) how RGBM is incorporated into recreational diving. You may still need a shovel to get through some parts of it though. :wink:

    BTW, life will be much simpler if you can talk your dive buddy into getting the same DC. Buhlman and RGBM pretty much part company at the first stop.
     
    denisegg likes this.

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