snorkel after diving - No fly time risk?

Discussion in 'Basic Scuba Discussions' started by Johnmpcny, Apr 19, 2011.

  1. Johnmpcny

    Johnmpcny Surface Interval Member

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    If I snorkel the off diving day before or even morning of my return flight after a week of diving does that add to my no fly time or risk? I do get down 20 to 30 + ft when I do this and was asked by one person since I equalize do I increase any risks when flying the next day or same day? It had never occurred to me.
     
  2. DBailey

    DBailey Scuba Instructor

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    Are you breathing compressed air at depth?
     
  3. knowone

    knowone  

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    I think I heard from an uncle of a friend's cousin's wive's son, or just read
    that it depends on the size of your snorkel
     
  4. Bedros A

    Bedros A New Member

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    In my limited experience...I dont think it would be a problem if you're snorkeling.
    If you're not breathing compressed air, then your no fly time should not be affected.

    However, if during the previous day's dive, you surpassed the NDL times and were forced into making a DECO stop, then intensive snorkeling (or any tiring physical work) is not recommended directly after the dive.

    Enjoy

    BA
     
  5. awap

    awap Well-Known Member

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    Submersion will increase the PP of nitrogen in you body and effect the off-gassing process. It can even result in increasing the body's nitrogen loading. In an extreme example, Japanese pearl divers (free divers) have been known to get the bends.

    That said, I don't think I would worry much about a total bottom time of 5 to 10 minutes at 20 to 30 feet. But, you always have the option of just remaining on the surface and not taking any added risks.
     
    AbyssalPlains and knotical like this.
  6. Karibelle

    Karibelle Scuba Instructor

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    I had to read this a couple of times to realize you said "total" and didn't mean all at once. I thought wow... that guy can really hold his breath.

    duh. :shocked2:
     
  7. Kenny13

    Kenny13 New Member

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    I think you and I read that the same way lol. I was thinking the same thing.
     
  8. nomro

    nomro New Member

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    What I know , if the air is not compressed then dont worry about it . plus how many minutes did you spend below the surface ?
    What is important from my point of view (I'm not a doctor) is the no fly time on your dive computer that is based on actual diving .
     
  9. Downing

    Downing Surface Interval Member

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    On an episode of Planet Earth I watched an Indonesian (I think) free diver who can hold his breath for up to five minutes at 60 feet. Incredible.
     
  10. knotical

    knotical perpetual student Staff Member

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    + 1 what awap said.

    The air in your lungs while free-diving is compressed, to the ambient pressure, so there is some increased risk of DCS. However, in the scenario described by the OP, the increase is likely extremely negligible.
     
    oldnotdead likes this.
  11. Charlie99

    Charlie99 New Member

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    Johnmpcny -- you didn't ask about freediving after diving, but here's some free advice that is worth what you've paid for it .....

    It's not a good idea to do any freediving for the first several hours after diving. The problem is that it is common for you to have some small bubbles in the venous side of the circulatory system for a couple hours after diving. They don't normally cause any problems because they are filtered out by the lungs. People with a heart defect called PFO can sometimes have problem, because the PFO can open up a direct path between the two sides of the heart and let the small bubbles through into the arterial side ... often the opening opens up when coughing or when you hold your breath when lifting something heavy.

    Bubbles in the blood on the arterial side can block capillaries, preventing blood from getting to critical bits of your body, like the brain.

    When you freedive, the increased pressure will reduce the size of the bubbles in the venous system, thereby letting some of them get past the lungs. Then as you come back to the surface, the bubble will expand back to the larger sizes that can cause problems.

    The above cautions don't apply to freediving the day after diving, since you won't have any bubbles in your venous system at that point.
     
    DocCarl likes this.
  12. Bedros A

    Bedros A New Member

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    In the OP's case, the increased chance of DCS is minimal...near nonexistant.

    1 breath-held descent will not cause an increase in DCS because of the limited amount of air you have in your lungs.

    The documented cases of bends in pearl collectors is because they do this A LOT during a very short period. In many cases, pearl divers (especially freediving pearl hunters, such as Japanese "Ama" Divers) needed to collect nearly one ton of oysters in order to obtain three to four high quality pearls.

    PS: I've always been fascinated by pearl divers...one tough breed of divers :D


    BA
     
  13. fresh_fish

    fresh_fish New Member

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    If you want to be safe, look at the tables, and calculate it as 5-10 minutes at 20-30 ft.

    The physiology is still there, no matter what you breathe from. Your body still circulates the compressed gas from your lungs while you are looking, and it will expand when you come back up. Yes it is minimal, but it is still happening and each dip will add to the amount that needs to come out of your tissues.
     
  14. temet vince

    temet vince New Member

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    Snorkeling will not add nitrogen to your body since you are not breathing compressed air. It shouldn't even affect the residual nitrogen already in your body since there won't be a significant volume change within.
     
  15. temet vince

    temet vince New Member

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    As far as I'm aware, this is incorrect.

    Unless your body volume changes under depth (ie, your body is squeezed so hard that it changes volume), then the pressure inside your body cannot and will not change.

    Our body puts up with pressure quite well. In fact it's under a lot of pressure at the surface. Adding 1 or 2 more atms shouldn't change our internal volume.

    Edit: Perhaps the area around the lungs does compress some. I doubt it would be a significant amount, but I could see it being enough to cause the problems that Charlie99 alluded to above.
     
  16. fisheater

    fisheater Divemaster Candidate

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    Increasing pressure on a liquid or solid doesn't result in proportional volume changes. The pressure is transferred through the human body without substantial volume change because it's mostly either a solid or A liquid. However, the air spaces, including bubbles in tissue or blood will contract due to the pressure around them.


    Sent from my iPhone using Tapatalk
     
  17. temet vince

    temet vince New Member

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    I'm not quite sure what you're meaning to say, so here's a breakdown of 3 simple well known "solids" under pressure:

    1. Scuba air tank. Very rigid. Thus, the air inside does not compress more at a greater depth.
    2. Plastic bottle with cap on. Not very rigid. Thus, the container shrinks with depth, decreasing the volume and increasing the pressure within.
    3. Human body. Not super rigid, but way more rigid that a plastic bottle. There will be some compression in the lungs, especially at deeper depths, but that difference is small.
     
  18. knotical

    knotical perpetual student Staff Member

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    We disagree. Your lungs expand and contract significantly every time you breathe. When you breath-hold submerge, your lungs contract (are compressed) as if you were exhaling.

    When a snorkeler (on the surface) submerges and becomes a free-diver, physics dictates that his/her lung will compress. Recall from open water class what happens to balloons.

    The air in a free-diver's lungs is compressed while he is underwater. That is why aggressive, repetitive, free-divers can suffer DCS. See, for example: Taravana - Wikipedia, the free encyclopedia

    However, in the example cited by the OP, the DCS effect is vanishingly small, even though the lung compression is dramatic.
     
  19. bleeb

    bleeb Single Diver

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    knotical already corrected some issues in another post, but since there seem to be several potential hazardous errors in this one as well, it seemed worth explicitly highlighting them.

    Actually, fresh_fish (and all the others who have stated this in this thread) are correct.

    When diving, the pressure inside your body is the same pressure as outside. Your body is mostly liquid, and it only takes a minuscule volume change for quite a significant pressure change. Gas pockets are subject to Boyle's Law, which is why you clear your ears while diving: to allow passages to stay their normal size by venting gas at ambient pressure into them. Lungs stay the same size because they're constantly being vented by breathing ambient pressure gas.

    Lung tissue has the strength of wet tissue paper, and it's ability to retain any size under pressure is negligible. They're completely subject to Boyle's Law, i.e. descending to a depth of 33 fsw without breathing in will cause their size to drop in half inside your rib cage. Going even deeper without gas to replace the volume will cause them to shrink proportionately. Freedivers going deep routinely acknowledge and face this issue.
     
  20. temet vince

    temet vince New Member

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    Ok, so I guess the lungs compress much more that I thought!
    I'll be the first one to admit I was wrong. Sorry about that. :(

    I guess my biggest confusion was that you say the body changes pressure inside to equalize outside, when I assumed that the skin and muscles (and bones too) acted as a rigid platform to resist pressure changes.

    I'll have to do some more research now!

    Should I delete my previous posts?

    Also, why doesn't your blood pressure change and kill you?
    In addition, how does the inside of your body "magically" gain the pressure it experiences outside of your body? To change pressure, you either need a change in temperature, a change in volume, or a change in the amount of material itself. There isn't a temperature change, or you would either freeze to death or overheat, and there can't be a volume change in your entire body or you would die (the blood pressure question listed above), and your body obviously isn't adding or deleting itself. I'm just having a hard time reasoning how your internal pressure can change like that, at least scientifically.
     
    Last edited: Apr 21, 2011

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