Nowadays divers have access to modern demand value
regulators and pressurized scuba tanks. These innovations have solved the
problems associated with the older techniques.
For every 33 feet (10 m) deeper
you dive, pressure increases 1 atm (one atmosphere). When you dive deeper, your
lungs and chest have to counteract the force caused by the pressure. This is
due to the fact that air is easily compressed. If you are breathing surface air
it's even harder. The reason breathing surface air down below is harder is
because that air stays at 1 atm.
Pressurized air is what you need in order to counteract the
increased pressure. Also, when you go deeper gases in your body compress
somewhat. The amount of compression that occurs is small but significant. At
sea level, air is approximately 78% nitrogen and 21% oxygen. Also present are
gasses, mostly argon, in trace amounts. Unfortunately, as pressure underwater
changes, the nitrogen and oxygen mixture changes. In order to maintain the
optimal concentration of oxygen, a modern regulator must be used.
The great thing about modern scuba diving air delivery
systems is that they compensate for these circumstances as they occur. The
result is just the right mixture of nitrogen & oxygen and pressure for
divers, as they go deeper in the water. Most dives are recreational and thus
done using a mask that covers the nose and eyes. Of course, breathing is done
through the mouth.
This situation results in a problem. The problem is that the
diver's mouth is wrapped around the mouthpiece portion of the regulator. When
you breath in, air comes into your lungs. First your lungs use the inhaled air
and then they exhale the remaining air. Part of the exhaled air is carbon
dioxide.
Typically you inhale 21% oxygen and then exhale 18% oxygen.
The difference is 3%. The 3% is carbon dioxide. Unlike carbon monoxide, carbon
dioxide isn't so toxic to breath. However, if you breath too much of it, it
cuts into the amount of oxygen you can consume.
After a while, that would result in you not getting enough
oxygen. Oxygen starvation causes disorientation, light-headedness and perhaps
even death. The modern regulator and tank system vents exhaled gas into the
surrounding ocean and that solves this problem. If you were to exhale through
your nose while underwater, you would fog up the glass on your goggles and you
would not be able to see properly.
Modern configurations are mostly open circuit 2-stage
regulators. The "father" of the modern Aqua-Lung is Jacques Cousteau.
He and Emile Gagman designed and build it during world war two and it was only
one stage.
In either the case of a one stage or a two-stage system,
breathable air is delivered to the diver that matches the ambient pressure of
the diver.
Air is pressurized to 200 atm inside the tank. In the case of the
2-stage system, the first stage reduces pressure to about 10 atm. A demand
regulator in a two-stage system, brings the pressure down again to that if the
surroundings.
The result is that divers gets air at the best pressure for
their lungs, thus counteracting the ambient pressure. The diving systems of
today provide safe and healthy air, reliably to scuba divers while underwater.
