I'm sorry but that's not correct. At least according to when I was taught
dive physics. One atmosphere of pressure is every 33 feet of sea water. At
sea level, above the surface of the water you are at one atmosphere of
pressure. Zero atmospheres of pressure would be a vacum. As you descend in
salt water (it's slightly different in fresh water but not by much) to a
depth of 33 feet you're at two atmospheres of pressure, 66 feet equals 3
atmospheres, 99 feet 4 atmospheres etc.... 1.5 atmospheres of pressure is
16.5 feet of sea water.


Jerry




"Glenn Ashmore" wrote in message
news:F5Cpb.875$62.52@lakeread04...
One atmosphere of pressure (14.7 psi) is 33 feet of seawater. THe .445
is correct but your math is wrong. 1.5 atmospheres would be about 50
feet. Regardless, the normal pressure differential that our lungs
produce is about 12 millibar or .17 psi. A person in very good health
can inhale at a maximum pressure differential of about 100 milibars or
1.45 psi. That is about 39 inches of seawater.

Just to verify the figures I went out to the boat shed, cranked up the
vacuum system and tried to breathe from the vacuum tube. I couldn't get
any air after 1.3 psi but I have probably inhaled more than my share of
Cabosil.



Rick wrote:

Jim Richardson wrote:


2) The pressure at say, 7 feet depth, is about 1.5 atmospheres,


The pressure at say, 7 feet depth, (in seawater) is about 3 psig. It
would take another 9 feet to reach 1.5 ats.

Seawater pressure increases at around .445 psig per foot.

Rick


--
Glenn Ashmore

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