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Re: [PSUBS-MAILIST] Re: Your Message Sent on Thu, 14 Feb 2002 13:38:48 +0000
Hi Lew,
Not a typo though I might have the depth off by a few feet. Certainly not
by 90 (100-10). The difference between your experience and my concern is this.
Free diving starts at the surface. You breath in the air at the surface at
the ambient pressure at the surface. As you dive down your lungs and other
bodily air spaces compress as you go down to depth. The air will even compress
a bit. You might even feel a squeeze on your ear drums. Then as you come up
to the surface the air spaces uncompress and you get to the surface with
air at the same ambient pressure your started with.
In wet subs, scuba diving or in any use of compressed air breathing here is
the problem. At a depth, say 32 feet, when you take in a breath the air you
breath will be at the ambient air pressure of the water at 32 feet deep. That
pressure is twice the ambient air pressure at the surface.
So if you take a nice deep breath at 32 feet down and come up to the surface
you now have air in your lungs at twice the ambient air pressure. It will
try to expand your lungs to twice their original size. There is a term for
that kind of lung damage but I can't think of it now. It is life threatening.
The way around this is to beathout while surfacing. One of the cool tricks
you learn learning scuba diving is going down to 40 or so feet, taking
a breath, and yell "AAAAAHHHHH" as you surface. The expanding air in
your lungs makes up for the air you "AAAAHHHH" out.
Well not really a trick. This is one of the emergancy training procedures
you are taught in scuba training. It is called "emergancy ascent". Just in
case one of your hoses blows, or a disk pops and you loose all your air and
your buddy is not around (bad thing) and you have no choice except doing an
"emergancy ascent".
Stuff like this is why I recommend everyone who messes with subs to take
scuba certification. Reading about it is one thing. Actually doing it
makes it real. Remember, it's the little things, like holding your breath,
that can kill you.
Regards,
Ray
> Date: Thu, 14 Feb 2002 11:49:47 -0800 (PST)
> From: Lew Clayman <lew_clayman@yahoo.com>
> Subject: Re: [PSUBS-MAILIST] Re: Your Message Sent on Thu, 14 Feb 2002
13:38:48 +0000
> To: personal_submersibles@psubs.org
>
> --- Ray Keefer <Ray.Keefer@Sun.COM> wrote:
>
> > mere fact that if you hold your breath at 10 feet will kill you
> > if you surfaced because your lungs will expand and explode.
>
> Please tell me that this is a typo, possibly s/b "100 feet?"
>
> I spent several childhood summers free-diving to 16' or so, never got anything
> worse than an ear infection...
>
> -L
>
> =====
> "The most important things in life are good friends and a strong bull pen."
> - Bob Lemon
> =====
>
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