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Different Blends of EANx

Discussion in 'Basic Scuba' started by Aerosynth, Jul 29, 2010.

  1. Aerosynth

    Aerosynth Nassau Grouper

    # of Dives: 25 - 49
    Location: Midwest/Central U.S. is where I hang my hat. Where
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    Currently studying my EANx certification book for my class next week. I am starting to understand the different applications of the standards, 32 and 36, and starting to grasp how higher/lower mixes are beneficial [-]in different ways[/-] for different dives.

    I was just curious... though... to hear from experience... have any of you used mixes other than 32 or 36? And if so, what were they and what applications did you use them for? Just trying to see the bigger picture here. Thanks.
     
  2. eponym

    eponym Master Instructor

    # of Dives: 1,000 - 2,499
    Location: Oregon, USA
    1,608
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    Have computed and used "best mixes" for deep dives, especially on decompression dives, usually significantly less than 32 to keep ppO2 within sane bounds. And then carried 40 or 50 percent O2 in sling bottles for the shallower decompression stops.

    This is of course outside the scope of basic recreational diving. On recreational charter boats I'll dive what they fill and sometimes it's a bit shy of 32. It's important to verify each fill yourself. I've often heard the term "slightrox" used for lighter mixes.

    -Bryan
     
  3. clifftondiver

    clifftondiver Divemaster

    # of Dives: 200 - 499
    Location: San Jose, Ca
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    I've used mixes ranging from 28% to 40%. The 28% was for a wreck class in San Diego and the 40% was on a dive which was long, but not super-deep (our agreed basement was 50 feet). Both of those dives were in doubles, so the amount of gas was less of an issue than NDL. When deciding on a mix, you have to weigh your SAC rate (gas supply) vs. depth (O2 exposure) vs. desired time spent at depth (NDL). When you factor all of those together, you'll come up with mix best-suited for that specific dive.
     
    Last edited: Jul 29, 2010
  4. sardiverdan

    sardiverdan Nassau Grouper

    # of Dives: I just don't log dives
    Location: California
    120
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    For the most part type I or 32% or type II 36% will be used for most non deco applications. Some divers use 40-80 EANX for deco needs. I just use 100% in my deco cylinder. Many dive shops will "bank" their nitrox which means they will only sell you 32% or maybe 36% because that is what they have pre-mixed. If you use a shop that supports more of the tech side of the dive world you will have a better selection of mix. On another note, just like any other cert in the dive world, a basic nitrox cert will only allow a certain percentage. When I learned nitrox back in the day I had to take basic, advanced, and technical nitrox. That has changed today and many of the advanced nitrox classes are folded into deco or heliair/helitrox class just fyi
     
  5. Aerosynth

    Aerosynth Nassau Grouper

    # of Dives: 25 - 49
    Location: Midwest/Central U.S. is where I hang my hat. Where
    114
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    Totally understand the importance of verifying mix after the cylinder is filled, too. Question is... do you guys (or recreational divers in general) usually invest in an oxygen analyzer as part of a gear set, or do you use the store's/boat's when needed? If I bought one, what type of cash would I be looking at?

    And the posts about the different mix percentages are great... I am totally getting a better picture here. Awesome! :)
     
  6. a22shady

    a22shady Loggerhead Turtle

    # of Dives: 50 - 99
    Location: New Jersey
    1,578
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    I use typically 32/36 but that is not always what you get. Sometimes it's off a little comes out with 31/33 +/-. and usually if I am done using eanx I will just use Air and dilute it till it's out. and this keeps me practicing using the tables that are not laid out. Not yet trained in anything above 40 so have not used it. and deepest I have been is only 90'. But typically best thing to do is get best mix for depth you are planning. If you download V-Planner they have a specific function for this. You have to verify and check all Nitrox fills before you leave the shop and sign a Log. atleast ones i have been to. Analyser I have seen for around 175-200
     
  7. idocsteve

    idocsteve Guest

    You don't need your own analyzer. The shop that fills your tanks will have one available so you can check the blend and pressuure when you pick up your tanks, or if they're supplied at the boat you can check them there using the analyzer they're sure to have there. Ask in advance to make sure there will be one for you to use.

    Analyzers are several hundred dollars and from what I recall there's a part that needs to be replaced periodically and it's not cheap. Save your cash for something you really need.

    To answer an earlier question I usually tell the shop that anywhere between around 31.5 and 33 is about right for most of my dives unless I'm going to a wreck that's deeper than usual. Most of my NY wreck dives are in the 60-100 foot range.
     
  8. Code Monkey

    Code Monkey Barracuda

    # of Dives: 200 - 499
    Location: Bay Area, CA
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    For me, it's been a continuum from 21% to about 36 or 37%. I had one live-aboard that added some blend into your previous tank. They started with air so the early mixes were pretty lean and got progressively richer over time. The last boat's EAN migrated pretty smoothly from 31% to 34%.

    I guess the moral is something you already know. Always analyze, always look up your maximum depth.
     
  9. sardiverdan

    sardiverdan Nassau Grouper

    # of Dives: I just don't log dives
    Location: California
    120
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    An O2 analyzer is a good investment if you can afford it. Most start around 300 or so and go up from there. You are going to start a fight with that question I have an analyzer for my HeO2N2 stuff and a setup for just nitrox will run you 300-400 for a reliable unit. You may ask some buddies if they would like to go in on one to save the cost. The sensors for these units can be expensive depending upon which unit you buy. For me I check the mix at the shop and then again before I use the cylinder. Many just check it at the shop and use it later with no problems. They use to teach students that a small particle in the cylinder could ignite the O2 and effectively burn it off inside the cylinder. I have never seen this happen or better yet have heard of this occuring but I am not here to say that it never could. There are also many posts on the net and books you can get that will show you how to make your own for less money
     
  10. ClarkKent

    ClarkKent Angel Fish

    # of Dives: 100 - 199
    Location: Vancouver B.C. Canada
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    I usually dive 36% at the end of the dive I usually have around 1000psi left, I then get my LDS to top it up with clean air and end up with about 27% for the second fill. It is essentially a slightly cheaper way of diving nitrox on each dive. My refill or second fill is variable and my NDL is less then it would be with a higher O2% but I don't often get that close to my NDL times anyways, so I just go with it except in the case where I am planing a specific dive at a greater depth.

    For the most part though 32% for deeper dives +- 100ft and 36 for < 100ft

    I don't own my own analyzer but I think they sell for approx $250-300

    http://www.leisurepro.com/Prod/OMSO...eld=Relevance&DescSort=0&Description=on&Hit=1
     

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