+ Reply to Thread
Page 1 of 7 1 2 3 4 5 6 7 LastLast
Results 1 to 10 of 70

Thread: Evidence based guidelines on gas density planning

  1. #1
    New Member Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell's Avatar
    Join Date
    May 2005
    Location
    New Zealand
    Posts
    683

    Evidence based guidelines on gas density planning

    Hello,


    The Rebreathers in Scientific Diving Workshop Proceedings (a workshop hosted by the AAUS, DAN, NOAA, and the US National Parks Service at Catalina Is in Feb 2015) were released today.


    You can download it here:


    https://dl.dropboxusercontent.com/u/...ngs%202016.pdf


    In this volume (which contains lots of interesting papers) there is (on page 66) a paper proposing the first published evidence-based guidelines for planning gas density in rebreather dives (or any dives for that matter) in order to avoid dangerous CO2 retention. The paper contains simple examples of how to calculate gas density for any gas mix at any depth.


    I hope you find it interesting. I (and I am sure Claudia also) would be happy to answer any related questions.


    Simon M

  2. #2
    RBW Member EngelenD is a jewel in the rough EngelenD is a jewel in the rough EngelenD is a jewel in the rough EngelenD is a jewel in the rough EngelenD is a jewel in the rough EngelenD is a jewel in the rough EngelenD is a jewel in the rough EngelenD is a jewel in the rough EngelenD's Avatar
    Join Date
    Apr 2011
    Location
    Belgium
    Posts
    1,085
    rEvo III rMS

    rEvo is all you need!!!!

    Re: Evidence based guidelines on gas density planning

    Thanks !!!!!!!


    Send from my Shearwater Nerd

  3. #3
    RBW Member DragonZA is an unknown quantity at this point DragonZA's Avatar
    Join Date
    Dec 2015
    Location
    United Arab Emirates
    Posts
    22
    Poseidon mk VI

    Re: Evidence based guidelines on gas density planning

    Thank you sir, as always.

  4. #4
    RBW Member dreamdive has disabled reputation dreamdive's Avatar
    Join Date
    May 2007
    Location
    Delray Beach, FL
    Posts
    1,245
    Pathfinder, rEvo, Explorer

    Meg, PrismII, Titan, Optima, 7

    Re: Evidence based guidelines on gas density planning

    That is awesome Simon. Thank you very much for your great work throughout the years and sharing it! Many thanks to all the other contributors of this paper!


    Looked at the calculation which works great for OC density calculation. For rebreathers, divers have to account for their [PO2] in their loop if they want to be even more accurate. :)

    Claudia

  5. #5
    RBW Member exposure is an unknown quantity at this point exposure's Avatar
    Join Date
    Jun 2011
    Location
    Paris, France
    Posts
    46
    APD Evolution+

    Re: Evidence based guidelines on gas density planning

    Thank you very much Simon for sharing these works with a so pedagogic approach. It is always great to read.

    I have a question that may be out of scope. How your ideal gas density of 5,2 and absolute maximum of 6,2 can evolve for open circuit diver (less static lung load and less equipment-related breathing resistance) and/or for bail out strategy where it can come from CO2 hit (scrubber breakthrough).

    Yvan

  6. #6
    New Member Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell's Avatar
    Join Date
    May 2005
    Location
    New Zealand
    Posts
    683

    Re: Evidence based guidelines on gas density planning

    Quote Originally Posted by exposure  View Original Post
    Thank you very much Simon for sharing these works with a so pedagogic approach. It is always great to read.
    Ha, thanks Yvan..... I always worry the "pedagogic approach" might offend some people. I am well aware that this forum in particular is populated by divers whose knowledge is already extremely good on subjects related to rebreathers.

    Quote Originally Posted by exposure  View Original Post
    I have a question that may be out of scope. How your ideal gas density of 5,2 and absolute maximum of 6,2 can evolve for open circuit diver (less static lung load and less equipment-related breathing resistance) and/or for bail out strategy where it can come from CO2 hit (scrubber breakthrough).
    Yes, an obvious question. I am fairly sure Gavin has similar data for OC. I have emailed him to clarify. If anything, the risk with OC might be slightly less for the reasons you point out, but it is not just equipment resistance that is important as I am sure you know. Density also affects the work of breathing by increasing resistance to flow through the diver's own airways, and by increasing the likelihood of dynamic airway compression (which is discussed in the paper).

    I will get back to the forum when I hear Gavin's take on the OC question.

    Simon M

  7. #7
    New Member Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell's Avatar
    Join Date
    May 2005
    Location
    New Zealand
    Posts
    683

    Re: Evidence based guidelines on gas density planning

    Quote Originally Posted by dreamdive  View Original Post
    For rebreathers, divers have to account for their [PO2] in their loop if they want to be even more accurate. :)

    Claudia
    Correct. You would have to perform a calcuation of what exactly is in your loop first if you want to be really accurate. Thanks Claudia.

  8. #8
    RBW Member exposure is an unknown quantity at this point exposure's Avatar
    Join Date
    Jun 2011
    Location
    Paris, France
    Posts
    46
    APD Evolution+

    Re: Evidence based guidelines on gas density planning

    Thank you Simon for the clarification. I hope I was correct by using "pedagogic approach" 'cos I can be very clumsy with english language sometime :)

  9. #9
    RBW Member deepdave is an unknown quantity at this point deepdave's Avatar
    Join Date
    Sep 2015
    Location
    Essex UK
    Posts
    64
    Inspo Vision

    Re: Evidence based guidelines on gas density planning

    Hey Simon, great article again, thanks for sharing.


    On page 45 Para 3, it talks about checking the linearity of the cells by ..."flushing the rebreather loop with 100% oxygen at a depth of 66ft (20m) prior to decent."

    Comparatively speaking I'm very new to the RB world so I'm sure I've misinterpreted something, but wouldn't a flush at this depth result in a Po2 of 3bar and a serious dose of Hyperoxia?


    Dave

  10. #10
    Enjoying the silence Lake_Tahoe_Diver will become famous soon enough Lake_Tahoe_Diver will become famous soon enough Lake_Tahoe_Diver will become famous soon enough Lake_Tahoe_Diver's Avatar
    Join Date
    Feb 2006
    Location
    Reno, Nv. (Lake Tahoe)
    Posts
    287
    Prism Topaz

    Kiss Sport

    Re: Evidence based guidelines on gas density planning

    Thank for providing the information. It makes us all better divers with knowledge.

+ Reply to Thread
Page 1 of 7 1 2 3 4 5 6 7 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts