Re: Power Snorkel, Snuba, or Helmet Diving?

Odysseus <x...@xxx> wrote:

I took a complete open water scuba course about twenty years ago.
I passed the classroom and pool portion with flying colors but
did not complete enough open water dives to get certified.
Here is my analysis of snuba and helmet diving.

Air pressure at sea level is 27 psi (pounds per square inch).

A minor error: its 14.7psia, which can be rounded off to 15psi.



This is one atmosphere. Every 33 feet you go down in sea water,
the air pressure increases by one atmosphere. If you are down at
35 feet, you will be at two atmospheres or 54 psi.

(30psi)


In order to
breath, you must be breathing compressed air at the same pressure
as the surrounding sea water. The air pressure inside you lungs
must me the same as the water pressure outside your lungs.

And the amount of pressure differential which can cause a rupture of
the Aveloi in your lungs is approximately 2psi negative pressure
(suction). The human body can withstand a bit more positive pressure
(blow), which is why we can blow up balloons.

Otherwise, the force on your lungs would be so great, you would not
be able to breathe.

The classical illustration (and one that many of us tried as a kid) is
to go try a 3ft long snorkel in your swimming pool: the human body
simply cannot draw air from even 3ft underwater.



If you are breathing compressed air, you need
to equalize the pressure in your ears and sinus cavities or you
will experience a squeeze and be extremely uncomfortable. With
snuba or scuba gear, you pinch your nose and exhale forcefully
through your nose. With helmet diving, that will be problematic
since the helmet will prevent you from pinching your nose. I
think helmet diving will add another complication. In order to
keep the water from leaking in, the air pressure would probably
need to be slightly higher than the surrounding sea water.

The helmets are open on the bottom, and most people can reach a hand
in to their face to pinch to equalize their sinuses, etc. Also, with
it being open on the bottom, the pressure inside can't exceed the
local ambient .. of course, what this also means that if you tipped
the helmet, you'll lose your air bubble (air supply) until the pump
replaces it.


I am over fifty, have sinus problems, asthma, high blood pressure,
and I'm not in great physical condition. My conclusion is that
snuba or helmet diving will be very risky for me.

Unfortunatly, many of the 'accidents' that occur today in these water
sports are usually related to relatively poor health, combined with
the stress of simple exercise. In the meantime, PADI is "pooh-
poohing" the need to actually test & evaluate for good basic fitness,
health and even the ability to be a good swimmer, all in their effort
to increase sales through a broader customer base. They're even now
promoting kids as young as 12 years old to dive, even though there's
medical studies which have shown that it inhibits bone growth.

Instructor Larry "Harris" Taylor has good webpages on this medical
issue as well as others. Here's his "Why I do not train Kids"
webpage: <http://www-personal.umich.edu/~lpt/kids.htm>
And here's his top homepage: <www.mindspring.com/~divegeek/>

Worth reading for anyone who's interested in knowing what is known
about the risks, instead of just what the industry mouthpieces want
you to hear.



-hh

.

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