|
Pittsburg, Kansas | Well there is zero differential pressure on the ears. Because you equalize them on the way down.
But the pressure on the body as a whole and the air pressure you are breathing at a depth of 180 feet seawater is pretty much as follows (with farmer rounding before someone corrects me with exact figures).
One atmosphere of pressure on land about 14.7 psi. But we reference it on our tire gage as zero. That is the weight of air from outer space to sea level.
One atmosphere of pressure under the weight of water is 33 feet. 14.7 psi.
180 feet depth/33 feet seawater equal 5.45 atmospheres additional pressure. (additional to surface pressure, so total 6.45 atmospheres to figure partial pressure of gas absorption).
5.45 x 14.7 equal 80 psi.
So there is 80 additional psi pressure exerted on the body. This means the diving regulator has to deliver air to the mouth at 80 psi greater than ambient pressure. So I am breathing 80 psi air down there but I can't tell it because the outside pressure is equivalent. Cool, huh?
In other words, if you had a shop air compressor in a boat with 81 psi and took the hose end down to 180 feet, air would bubble out the end at 1 psi. Crazy.
But the nitrogen gas and oxygen gas in the air is being absorbed into the bloodstream at 6.45 times the rate (partial pressure law) as at the surface (5.45 + 1 atmosphere at the surface for a total of 6.45 atmospheres pressure). This liquefied gas has to escape back into our exhaust breath via our lungs as we go more shallow. If we go up too fast or have absorbed so much gas it turns back into gas too quickly bubbles form in the bloodstream causing blockage in capillaries and he gets the "bends" otherwise known as decompression sickness.
So nitrogen accumulation is the limiting factor for normal divers. Normal sport divers stay within no decompression limits. They go up shallower before they absorb too much nitrogen. They don't have to decompress.
Oxygen concentration becomes toxic somewhere between 1.4 and 2.0 concentration. So deep diving on air Oxygen toxicity also becomes a limiting factor. At 187 ft depth breathing air the concentration is 1.4. Anything beyond that is kind of playing Russian roulette. On using 32% nitrox instead of air ( which I usually do for regular diving) 1.4 is 111 feet depth. 1.2 is considered safe, 1.4 emergency depth. So diving nitrox usually limit depth to 100 feet.
I hope I got all that right. I was trained in 1968 then again in 1982 when major changes in equipment had happened. Nitrox trained probably 20 years ago.. That is a long time to remember that stuff. Dive computer keeps track of it all. Used to have to use dive tables and a watch for deep dives
More than you ever wanted to know. Someone correct me if I got some of it wrong.
Edited by John Burns 1/14/2025 20:06
| |
|
Antique Anchor #2 scubadiving
