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Nitrogen absorption...

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  • #46
    Originally posted by Grizzly 2 View Post
    You're mixing apples with oranges here. It isn't 1 atmosphere, it's the atmosphere. Higher, it becomes the stratosphere, the ionosphere, etc. None of those terms relate to air pressure values.

    As one dives to 30-feet (actually 29.4 feet), he may ascend without decompression. At any depth below that, he will require decompression. This exemplifies and supports the the 1/2 ATM rule.

    An interesting aside: around 1969, SCUBAPRO came out with its first "Decom Meter". Worn on the wrist, this cumbersome gadget included "Mystery Element X", and was designed to aid in dive calculations as they related to decompression needs.

    I didn't say either of those terms (stratosphere, ionosphere) applied to pressure because I never used those terms. And as far as our entire atmosphere being 1atm of pressure that wasn't me who discovered that, it was a fellow named Torricelli hundreds of years ago.

    Your statement of being able to dive to 30 feet and ascend without decompression was proven by the Navy to be false. The Navy also disproved your statement about going below 30 feet requiring decompression. Because decompression is determined not by one factor (pressure) as you seem to imply but by two factors - time and pressure. Stay at 30 feet for more than Navy dive table no decompression limits (approx 3 hours at 30 feet) and you are in decompression mode. Again, you can't change physics so whether you believe that or not means nothing.

    So your two statements, both of which the Navy proved are false, do you not support this phantom "1/2 atm" rule you keep citing.

    I'll ask again - please post any documentation proving this phantom '1/2 atm' rule. Because the Navy disproved everything you stated above about how pressure affects us when diving. Documentation - post it. Stop making things up and post your proof. I did. Why can't you?


    • #47
      This thread wins the 2017 Alaska Outdoors Forum thread of the year award for "Painful Constipation".
      "Life Is Either a Daring Adventure or Nothing" - Helen Keller


      • #48
        Just saw this thread and thought I would chime in. For background, I used to manage a dive shop in Hawaii, before we moved here to Alaska, and in that capacity ended up with a PADI Divemaster certification. That was back in the 1980's. There didn't seem to be much money in instructing in our case (we had 10 instructors working for us at the time, and I knew what they were doing and how much they made), so I took a different fork in the PADI trail that was more in line with my goals. I've done a little diving in Alaska and would love to do more. Deepest dive here was 130' in Seward; basically a bounce dive off a pinnacle out toward Fox Island.

        In all this discussion the focus has been on getting "the bends", but I'm not seeing anything about dysbaric osteonecrosis. That's the one where nitrogen comes out of solution (reverts to a gas) in bone tissue and, over time, causes bone tissue to die and become brittle. It's the bane of commercial divers especially. It's possible to experience it without getting the immediate joint pain you get when gas bubbles develop in the joints. As I'm sure you guys are aware, bone tissue has a slower absorption / release rate than joint tissue. So just because you don't get bent / feel immediate pain, doesn't mean there's no damage. You just don't see the results for several years.

        Never occurred to me that there were limits under 33 ft. That makes tons of sense, of course. Just one of those things I never thought of. I think my longest recreational dive was over two hours; it was on a shallow reef at night near Blowhole on Oahu (to the right of Sandy Beach). We were hunting lobsters and shells. Full moon, and totally flat seas; you almost didn't need lights. An unforgettable dive. We never even made it to 30' on that one; our average depth was 15'. I was using a steel 104, which allowed me a ridiculously long bottom time.

        Anyway, I thought I'd toss that log on the fire for rumination...

        Michael Strahan
        Site Owner
        Alaska Hunt Consultant
        1 (907) 229-4501


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