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How does your computer handle deep dives?

Discussion in 'Advanced Scuba' started by fisherdvm, Sep 23, 2018.

  1. jvogt

    jvogt ScubaBoard Sponsor ScubaBoard Sponsor

    # of Dives: 500 - 999
    Location: Lakewood, CO USA
    I'm not the most experienced on the board, but there are some things that need to be said clearly for the benefit of any beginners reading this thread.

    1) In 20+ years of diving I have never heard of or seen a PDC that considers GAS supply in it's NDL/Staged Deco calculations. How much inert gas is dissolved in your tissues has nothing to do with how much longer you can breath underwater. These are two completely independent items that must be separately managed.

    2) You should never undertake a staged deco dive without pre-planning your gas requirements, contingencies, and redundancies. Most non staged deco trained divers have no idea how to do this. Heading up at 1k psi is not a proper staged decompression gas plan.

    3) No one should ever have un-planned staged decompression requirements. There is no excuse. This demonstrates a complete lack of awareness and attention. "I wanted to see a pretty fish" and "The DM was not ascending yet" are not valid excuses. You are responsible for your own safety. Your PDCs will tell you on the surface before your dive how long you can stay at your planned depth. If its not long enough then extend your surface interval until it is or change your plan.

    4) Never plan to use your recreational PDC for decompression diving. In most cases the base algorithm was not designed for it and it is well out of its empirical testing range. Most trained technical divers run a much more conservative algorithm than the average recreational PDC.

    Did I miss anything?
    Scuba J7, RyanT and doctormike like this.
  2. doctormike

    doctormike Contributor Staff Member

    # of Dives: 1,000 - 2,499
    Location: New York City
    Maybe not, but you sure are good at summing thing up! Thanks...
  3. jvogt

    jvogt ScubaBoard Sponsor ScubaBoard Sponsor

    # of Dives: 500 - 999
    Location: Lakewood, CO USA
    Your PDCs deep stops are an arbitrary (Not Required) addition when you are within no stop limits. My guess is that when you exceed NDL your PDC falls back to the base decompression algorithm and stops inserting arbitrary safety/deep stops.
  4. Storker

    Storker ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 100 - 199
    Location: close to a Hell which occasionally freezes over
    Random data point: if you run Suunto's rec RGBM algorithm, if you go into deco you'll get a bunch of deco time @3m, but none at 6, 9, 12 etc.

    If I ever were to do a deco dive, I would never trust a rec PDC to give an even remotely sensible deco schedule.

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