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  1. #101
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    Default Re: Can't believe they sell this to people who are not trained.

    Quote Originally Posted by cainslie View Post
    It's clearly advertised as 3000psi which means it certainly will work below 6m.
    200 Bar, well capable of +6m depths, and even more dangerous as a consequence.
    Cheers,
    John Kilfoil

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  3. #102
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    Default Re: Can't believe they sell this to people who are not trained.

    Out of sheer interest and to test my memory I did some calcs on this .......

    0.5 l tank at 200 bar gives you 100litres of free air - ie not under pressure

    Assuming a Respiratory Minute Volume (RMV) of 25l per min gives you 4 minutes of breathing time - at the surface.
    The 25l per minute is an average value, could be more or less given different fitness values for individuls.

    Down at 10m it will only give you 2 minutes, probably less if you are using it in an emergency situation and breathing hard.
    At 20m less than a minute and a half.
    Safe Diving - Andy

    2013 Isuzu KB6 300 DC 4X4

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  5. #103
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    Default Re: Can't believe they sell this to people who are not trained.

    Quote Originally Posted by AndyT View Post
    Down at 10m it will only give you 2 minutes, probably less if you are using it in an emergency situation and breathing hard.
    At 20m less than a minute and a half.
    And, if you are stressed and anxious, it will probably be finished a lot earlier.
    Cheers,
    John Kilfoil

    Rover P6
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  7. #104
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    Default Re: Can't believe they sell this to people who are not trained.

    Quote Originally Posted by AndyT View Post
    Out of sheer interest and to test my memory I did some calcs on this .......

    0.5 l tank at 200 bar gives you 100litres of free air - ie not under pressure

    Assuming a Respiratory Minute Volume (RMV) of 25l per min gives you 4 minutes of breathing time - at the surface.
    The 25l per minute is an average value, could be more or less given different fitness values for individuls.

    Down at 10m it will only give you 2 minutes, probably less if you are using it in an emergency situation and breathing hard.
    At 20m less than a minute and a half.
    This assumes use like a scuba set. If you use it like snorkeling: I.e. hold your breath until you need to breathe, then take a deep breath and hold again, it will last a significant time. And that is exactly where the danger lies, if you rise even a little after breathing in at depth and not exhaling while doing so.


    C
    If you ain't livin on the edge, you're taking up too much space!

  8. #105
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    Default Re: Can't believe they sell this to people who are not trained.

    Deleted, Same as post #51
    Last edited by neoT; 2020/12/18 at 08:33 PM. Reason: Allready posted
    Neil

  9. #106
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    Default Re: Can't believe they sell this to people who are not trained.

    Quote Originally Posted by neoT View Post
    These guys say it's a scam.
    https://youtu.be/pZYWO0ylFoQ
    See page 3 post # 51.

  10. #107
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    Default Re: Can't believe they sell this to people who are not trained.

    Boyles Law.

  11. #108
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    Default Re: Can't believe they sell this to people who are not trained.

    Quote Originally Posted by C Africa View Post
    This assumes use like a scuba set. If you use it like snorkeling: I.e. hold your breath until you need to breathe, then take a deep breath and hold again, it will last a significant time. And that is exactly where the danger lies, if you rise even a little after breathing in at depth and not exhaling while doing so.


    C
    The no 1 and most important rule of Scuba diving.

    "Never stop breathing"

    That's it. No arguments. There is nothing more important, and it is with good reason

  12. #109
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    Default Re: Can't believe they sell this to people who are not trained.

    Quote Originally Posted by C Africa View Post
    This assumes use like a scuba set. If you use it like snorkeling: I.e. hold your breath until you need to breathe, then take a deep breath and hold again, it will last a significant time. And that is exactly where the danger lies, if you rise even a little after breathing in at depth and not exhaling while doing so.


    C
    I beg to differ.

    If you hold your breath until you need to breathe then you are going to take much deeper breaths to flush your lungs which ultimately will amount to the same thing as steady breathing.
    Repeat that a couple of times and the air available will last even less time.
    Safe Diving - Andy

    2013 Isuzu KB6 300 DC 4X4

    http://www.flickr.com/photos/andrews_underwater_images/


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  14. #110
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    Default Re: Can't believe they sell this to people who are not trained.

    Quote Originally Posted by Pietsweis View Post
    The no 1 and most important rule of Scuba diving.

    "Never stop breathing"

    That's it. No arguments. There is nothing more important, and it is with good reason
    True.
    But there is something to be said for holding your breath just a little. At 30m when viz is good, the tiny bubbles goes "ting" and the surge is minimal, perfectly adjusted buoyancy allows one to go up and down a little bit at a time by just inhaling, exhaling or holding breath at rhe right time. Direction adjustment with a twist of a fin. None of that flailing arms and scratching knees BS.

  15. #111
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    Default Re: Can't believe they sell this to people who are not trained.

    Remember, my problem with these sales were that they sell them to people who are not trained scuba divers, so expect them to do stupid things.

    With regard to holding your breath will use more air, not so. If you just breath normally, you are exhaling air that still has a lot of oxygen in it (or at least is not yet saturated with CO2). Personally, when I dive, I take deep breaths, and then let them trickle out VERY slowly, that way I only take one breath about every 1 minute. I know that this saves air, as my tanks always have much more air left in them than any-one else's when I surface after a dive.


    C
    If you ain't livin on the edge, you're taking up too much space!

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  17. #112
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    Default Re: Can't believe they sell this to people who are not trained.

    Quote Originally Posted by New View Post
    I remember these from watching Baywatch. (Alright alight, I also remember other things from Baywatch. Bouncy things).

    I always really wanted one!
    I thought you would have rather wanted Two of those bouncy things to play with?

    Drive: Nissan Hardbody DC TD 16V 2007
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  18. #113
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    Default Re: Can't believe they sell this to people who are not trained.

    Quote Originally Posted by waldo_g View Post
    True.
    But there is something to be said for holding your breath just a little. At 30m when viz is good, the tiny bubbles goes "ting" and the surge is minimal, perfectly adjusted buoyancy allows one to go up and down a little bit at a time by just inhaling, exhaling or holding breath at rhe right time. Direction adjustment with a twist of a fin. None of that flailing arms and scratching knees BS.
    Yup. The simplest way to spot a newbie diver is by how much they move.

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  19. #114
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    Default Re: Can't believe they sell this to people who are not trained.

    Quote Originally Posted by Spliffcat View Post
    Boyles Law.
    Correct(P1V1)/T1 = (P2V2)/T2

    Where

    P - Pressure
    V - Volume
    T - Temperature

    The laws of physics are not optional.
    Last edited by Olyfboer; 2020/12/19 at 04:12 PM.

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  21. #115
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    Default Re: Can't believe they sell this to people who are not trained.

    Quote Originally Posted by Olyfboer View Post
    Correct(P1V1)/T1 = (P2V2)/T2

    Where

    P - Pressure
    V - Volume
    T - Temperature

    The laws of physics are not optional.
    cute google

  22. #116
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    Default Re: Can't believe they sell this to people who are not trained.

    Quote Originally Posted by C Africa View Post
    Remember, my problem with these sales were that they sell them to people who are not trained scuba divers, so expect them to do stupid things.

    With regard to holding your breath will use more air, not so. If you just breath normally, you are exhaling air that still has a lot of oxygen in it (or at least is not yet saturated with CO2). Personally, when I dive, I take deep breaths, and then let them trickle out VERY slowly, that way I only take one breath about every 1 minute. I know that this saves air, as my tanks always have much more air left in them than any-one else's when I surface after a dive.


    C
    That is called skip breathing - http://thedivingblog.com/skip-breath...0be%20avoided.

    Skip breathing is basically when you interrupt your normal breathing pattern for too long by holding your breath for a few seconds, in between inhaling and exhaling. It is never recommended that you get into the habit of skip breathing since it can be very dangerous and counterproductive. By holding your breath for a few seconds, you are breaking the golden rule of scuba to always breathe. Secondly, you are actually causing CO2 to build up in your body, which will ultimately increase your breathing reflex, meaning you will breathe more and not develop an efficient-breathing technique. Finally, skip breathing and CO2 build-up will more than likely give you a post dive headache and lethargy, and in extreme cases you could even suffer a deep-water blackout, which could be fatal.
    Safe Diving - Andy

    2013 Isuzu KB6 300 DC 4X4

    http://www.flickr.com/photos/andrews_underwater_images/


  23. #117
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    Default Re: Can't believe they sell this to people who are not trained.

    SCUBA diving in Cape waters. Skip breathing gets entertaining when a 5 meter swell zooms over your pip. Ah the joys of being a mud prawn.
    Don't go deeper than 20 m anymore and only dive tropical water now.

  24. #118
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    Default Re: Can't believe they sell this to people who are not trained.

    Quote Originally Posted by Rustie View Post
    cute google
    Pre Google. I still memorise it from my days in the Navy and first year in the SADF's Wingfield Technical College where I was in the Boyle Division and accommodated right across the road from the Libertas Hotel in Goodwood, Cape Town. Had you read the thread completely instead of making a snide remark, you may have seen that I may know a bit about being underwater.

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