BREATHING
AIR AT DEPTH
The 21 percent oxygen in compressed
air can also be toxic, but not until
you descend well past the recommended
maximum limits for recreational diving.
So when diving with air within recreational
depth limits, oxygen toxicity isn't
an issue.
Recreational
divers sometimes use enriched air (also
known as "enriched air nitrox"
or "nitrox"), which has more.
than 21 percent oxygen. Enriched air
has some advantages regarding how long
you can stay underwater at a given depth,
but you can have oxygen problems using
it within recreatioral depth limits.
For this reason, enriched air diving
requires special training and some special
equipment requirements (to avoid combustion
problems possible with high oxygen levels);
reputable dive centers will not, provide
enriched air without proof of enriched
air certification.
So,
to avoid oxygen toxicity problems, don't
have (or try to have) your cylinder
filled with enriched air, unless you're
properly trained and certified. Don't
use a cylinder that's marked as being
an enriched air cylinder, (again, unless
you're properly trained and certified).
Nitrogen
Narcosis
Although nitrogen has no direct influence
at the surface, that changes as you
breathe it under sure. Underwater, at
depths approaching 30metres/100 feet,
nitrogen has a noticeable intoxicating
effect that intensities as you go deeper.
A diver affected by nitrogen narcosis
behaves as you might expect someone
to behave if intoxicated. Narcosis impairs
the diver's judgment and coordination,
and may create a false sense of security,
cause disregard for safety and other
foolish behavior. Nitrogen narcosis
can make a diver feel anxious or uncomfortable,
which can lead to panic or other poor
decisions.
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