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Maximum Operating Depth (M.O.D.) S.C.U.B.A. Diving On Air.

Discussion in 'Advanced Scuba Discussions' started by Boston Breakwater, Jul 7, 2020.

  1. tbone1004

    tbone1004 Technical Instructor ScubaBoard Supporter

    # of Dives: I'm a Fish!
    Location: Greenville, South Carolina, United States
    so the majority of recreational divers? sad but true...
    Dark Wolf likes this.
  2. johndiver999

    johndiver999 Manta Ray

    # of Dives: 500 - 999
    Location: Gainesville FL
    The BMI quoted was, by definition, in the obese range. Not sure if Seattle has a higher proportion of obese people, but a significant majority of Americans are overweight or obese, with even higher rates in some minority groups.
  3. dmaziuk

    dmaziuk Regular of the Pub

    Swinging a sledgehammer may work to your advantage: it's making you breathe harder and thus vent more CO2. You'd probably retain more CO2 if you were just drifting along not breathing much. Whether a particular diver on a particular dive would retain enough to cause "dark narc" etc. is the interesting question.
    Vicko likes this.
  4. BRT

    BRT not a soft touch ScubaBoard Supporter

    Not my experience with CO2 narcs.
  5. 100days-a-year

    100days-a-year Solo Diver

    # of Dives: 5,000 - ∞
    Location: NE Florida
    Most of my dives were down an anchor line. With little current, there was little perception of narcosis until pretty deep. When the current was running and it was difficult to get down, I would have to take a minute wherever the current slowed to slow my breathing or narcosis was much more noticeable. Most of the guys I dive with say the same. And thats 10s of thousands of dives at those depths between us. So I try to limit my exertion as much as possible.
    Boston Breakwater and Dark Wolf like this.
  6. drbill

    drbill The Lorax for the Kelp Forest Scuba Legend

    # of Dives: 2,500 - 4,999
    Location: Santa Catalina Island, CA
    I set my limit diving on air to ppO2 = 1.6, so about 220 fsw. However, I always stopped at 200 fsw (except the one time my brakes didn't work and I hit 201 fsw). Being near "Lost" Angeles, our atmosphere may have a lower percentage of O-2 (tee hee). Did many deep dives on air including repetitive dives. No significant narcosis back then at those depths (I had so much residual nitrogen in my body it wouldn't let any more in!). This was almost a decade ago. Today I generally limit my dives to 100 fsw max depth and dive air almost exclusively.
  7. ginti

    ginti DIR Practitioner

    # of Dives: 100 - 199
    Location: Lyon, France
    French federations (there are five of them if I am not wrong) allow recreational dives up to 60 meters with air (roughly 197 feet). They teach it at the "level 3" course, the link is in French, sorry :)

    Plongeur niveau 3 — Wikipédia

    A "diving director" (DP in the link, directeur plongee) must be in place, but as far as I understood he/she doesn't need to dive together with the divers who hold the level 3 card. To make an example, assume a diving club organize a big trip, and 30 people including a DP go with a boat to a diving site. The DP is present, so the level 3 divers can dive on their own to 60m. Also, they cand dive to 40m whenever they want, even without a DP present
    NothingClever likes this.
  8. ginti

    ginti DIR Practitioner

    # of Dives: 100 - 199
    Location: Lyon, France
    Hi halocline, a quick question for you: what do you consider recreational diving? Is a dive at 130ft/40m, open water, but very low visibility and cold water (let's say less than 10C/50F), and maybe even high current (is current the right English word? or flow? sorry I have no idea :) ) a recreational dive for you?
  9. leadduck

    leadduck Barracuda

    regarding the trimix depth recommendation, it's not about depth alone. In open water you can feel nitrogen narcosis coming and then reduce risk simply by going shallower. But that doesn't work inside a cave or wreck, hence I don't think it's overconservative if an agency focused on cave diving such as GUE recommends trimix already at 100ft.
  10. halocline

    halocline Solo Diver

    I was just using the standards set by the major recreational training agencies like PADI. So, 130ft max depth, clear path to the surface, no mandatory decompression. It's hardly an airtight definition, and I'm not defending it as such. It's just for discussions like this one, you need some sort of frame of reference, and following guidelines that literally millions of divers have been trained by (for better or worse) is a logical place to start. This is especially true in this thread because the OP made no mention of technical diving; actually his question was a little vague and arbitrary, and I probably should have just stayed out of it.

    There are certainly lots of 'gray area' dives where one person might think "this is a technical dive, I should only do it with the right tech diving training, equipment, and gasses" while another person would gladly do the dive with only recreational gear and training, on air. Who is right? That's where the opinions start!

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