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Nitrox benefits for Cozumel diving

Discussion in 'Cozumel' started by tracydr, Jul 23, 2013.

  1. Peter69_56

    Peter69_56 Divemaster

    # of Dives: 500 - 999
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    The day you ignore the reality of the situation might be the day reality serves you up a very bad outcome. A spinal bend can be permanent. What does it take to get one? A question no one can answer accurately as we are all individuals and thus exposed to the same risk at a differing level depending on us as unique beings.

    My wife did everything required (and more) to ensure the risk was low and got bent. I run close to the wind and to date (crossing all my fingers and toes) have not been touched.
     
  2. AggieDiver

    AggieDiver Contributor

    # of Dives: 200 - 499
    Location: Houston, Texas
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    For those who think going from a 0.001% chance to a 0.0005% chance isn't worth it, let me pose a different scenario. Forgetting the actual numbers, if I told you that you could go skydiving and gave you a choice of parachutes; and told you that the red chutes were packed in a new way that they were twice as likely to open safely as the blue chutes, but cost $5 per jump more, which chute would you pick? The risk of a chute not opening is already very very small...but what if you could cut that chance in half? What would you pay for that?

    When you look at it that way, the actual risk percentage numbers seem less important than the fact that you are doubling your margin of safety. I don't know that nitrox does that...but it might...so I use it every time it is available, because it is a small cost compared to the rest of what I am paying to go diving.
     
    kelemvor likes this.
  3. Skittl1321

    Skittl1321 Contributor

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    I think the numbers really do matter though. 0.001 to 0.0005 doesn't seem to be that big of a deal. But if I went from 0.1 to to 0.05, that seems to be worth the risk mitigation.

    To me, same with nitrox. If I'm going to Roatan and doing 2 boat dives, 2 shore dives, and then a night dive all in one day. That would definetly be worth it for me to get nitrox certified. But for right now, going to Cozumel, diving twice a day, it isn't worth the $165 class and then extra per tank. At least not yet. Especially because, for me, I can't imagine my air consumption is going to result in very long dives. People who talk about nitrox being practically free in Bonaire- I'd take the class.


    (And for the record- the instructor I mention uses nitrox and recommends it: for those wanting more bottom time, or for those doing A LOT of diving. He just doesn't think the dive nitrox on air profiles thing is worth it for the vast majority of divers. Keep in mind he was also teaching an OW class, and so adding nitrox adds a bit to the task loading getting ready to dive, though not much. It also adds risks in other areas while decreasing risk of DCS. His advice to an advanced diver might be different.)
     
  4. nimoh

    nimoh Public Safety Diver

    # of Dives: 500 - 999
    Location: Rochester, MN
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    Nitrox doesn't do that, your planning does.

    If you do a dive to 90' on EAN32 using NDL from air tables, then you get an increased margin of safety.

    However if you dive air to 90' using air tables, but don't come within 10 minutes of NDL, you get the same increased margin of safety.
     
  5. Lorenzoid

    Lorenzoid ScubaBoard Supporter Staff Member ScubaBoard Supporter

    # of Dives: I just don't log dives
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    If a parachute fails, you have a near-100% chance of dying. If you have a DCS hit, it could manifest itself in myriad ways. DCS can range from the relatively mild Type I to the relatively severe Type II, and even within those categories there is a range of possible effects on various parts of the body. I have to believe that included in the data that might give rise to a ".001 reduced to .0005" figure, there would be incidents of DCS that were extremely mild.
     
  6. Ron Lee

    Ron Lee Contributor

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    Not even close to accurate. The person should have a reserve parachute.

    ---------- Post added July 24th, 2013 at 10:46 AM ----------

    MOD Source: DiveNerd - Nitrox Maximum Operating Depth (MOD) Table

    Assume a ppO2 of 1.4, MOD for 32% nitrox is 111 feet and 187 feet for air.

    Scenario: You are on a wall-like dive in Cozumel, ocean side, at around 100 feet. You and your buddy (could be a spouse, real buddy, insta-buddy or just the random pairing during a dive) are at the end of the line as the group enters a swim-through to reach shallower water on the shore side of the reef.

    You were looking at something closely for a bit, maybe a juvenile yellowtail damselfish. When you look back to enter the swim through and check on the buddy, that person is below you and still sinking. You estimate their depth at 130 feet which is below the MOD for the nitrox 32 you are using.

    Assisting that diver (no one else is around) will result in the both of you going to around 150 feet before ascending. Assuming that you have the training and experience to assist the diver below you, do you bust the MOD limit for nitrox 32 or would you prefer to be on air?

    When I first heard of nitrox around the mid 90s, it was presented like snake oil. Longer bottom times and lower nitrogen absorption. I saw through that right away.

    Nitrox does allow longer dive times. I use two Suunto computers which appear to be relatively conservative (lower dive times). On at least one dive, I set one computer to air and the other to the nitrox level I was using. It makes a big difference. There have been a few times when I was on air and had to ascend earlier than the group because I was bumping up against deco. I can deal with a deco obligation but still have to clear it before surfacing, so ascending and staying above the group works on those few occasions required. I still surface with the group at the same time.

    Bottom line: I disagree with the notion that every recreational dive should/must be using nitrox. If others go that route, it does not bother me one bit.
     
    Last edited: Jul 24, 2013
  7. AggieDiver

    AggieDiver Contributor

    # of Dives: 200 - 499
    Location: Houston, Texas
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    I used the parachute comparison because both instances (chute failing to open and DCS hits) are uplanned events that have the potential to be lifethreatening. How life threatening DCS is obviously depends on how bad your hit is and where the nearest chamber is. How bad the chute not opening is depends on how high you are when it fails and whether you have a reserve chute that functions properly. Neither situation is one you would want to find yourself in, so depending on your level of risk aversion, you might use available tools (such as nitrox) in your planning to give yourself a margin of safety. Obviously as stated in this thread, some folks don't see the value in that, as they feel the level of risk on air is acceptable to them. But whether you see a value correlation in the increased margin of safety potentially gained by using nitrox (however large or small it may be) or not doesn't mean the margin of safety isn't there. It may not be meaningful to you in your risk planning, but that doesn't mean it is non-existent.
     
  8. Brules

    Brules Contributor

    # of Dives: 200 - 499
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    What in the world are we arguing over here?

    If you want to be safer, dive 32/36 on air tables.

    If you want more bottom time on 32/36, do it, wheter you use air or nitrox tables - who cares.

    If you want to not feel like you have sleeping sickness after a week of diving, use nitrox.

    If you are just the cautious type - then dive nitrox for whatever marginal safety factor it gives you. Piece of mind is usually worth it.

    If not, then don't.

    Why are we arguing over it lol? This is soooo stupid.

    I do a 2nd tank of 36% for the week on air tables. I feel better doing it. I am adding some safety factor and reducing my % of getting hit and I get a longer bottom time on my second dive because I breath less due to more oxygen. Is there anything wrong or incorrect about this? NO.

    So why are we arguing it?
     
    robint likes this.
  9. nimoh

    nimoh Public Safety Diver

    # of Dives: 500 - 999
    Location: Rochester, MN
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    on the same dive hanging out on the wall at 100', you realize you blew your NDL by 10 minutes. Would you prefer to be on nitrox 32?

    my point is as I said earlier, nitrox isn't more safe or less safe, dive planning does that.
     
  10. Sue Sue

    Sue Sue Contributor

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    Oh Noooooooo... "Dead Horse" post # 3 ...

    "NITROX !!! Can't forget Nitrox especially since the Nitrox in Cozumel actually smells like Coconut ....Really !!! "

    But Alas...here we go again .... :). LOL
     
    cvchief and Karibelle like this.

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