PADI EANx (2003) Subtitles

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[Narrator]
Time.

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When you're diving, sometimes
there just isn't enough of it.

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Somehow, it seems like the
better the dive, the sooner it ends.

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Much of diving's evolution has been
a struggle for more time underwater.

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We use better and more
effective exposure suits

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to help us to stay
comfortable longer.

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Dive computers give us far more
no stop dive time compared.

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And today, we can stay underwater
even longer, thanks to enriched air.

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Enriched air - sometimes called
nitrox - extends no stops limits,

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and when coupled with an
enriched air dive computer,

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provides more dive
time than ever before.

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Enriched air is most useful
in the 18 metre/60 foot

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to 30 metre/100 foot depth
range, because in this range,

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the dive often ends because you
run out of no decompression time.

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And, you'll find
enriched air really

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boosts your bottom time
when you make repetitive dives.

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The PADI Enriched Air Diver course
qualifies you to use enriched air nitrox.

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You'll learn its
benefits and drawbacks,

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special equipment
considerations,

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the procedures for obtaining
and analyzing enriched air,

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how to use enriched air computers
and dive tables to plan dives,

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and how to effectively manage some
of the possible risks associated with it.

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What, exactly, is
enriched air nitrox?

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As you may recall, air consists of 21
percent oxygen and 79 percent nitrogen.

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Enriched air has been
enriched with oxygen,

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so that it has more
than 21 percent.

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Enriched air 36, for example,
is 36 percent oxygen.

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As a recreational diver, you'll
typically use enriched air

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that has between 22
and 40 percent oxygen.

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Most of what you
learn in this course

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relates directly or indirectly
to this added oxygen.

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The primary purpose of enriched air
is to extend your no stop dive time.

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As you recall, it's nitrogen
dissolving into your body tissues

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that determines the
no decompression limits.

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Enriched air replaces some
of the nitrogen with oxygen,

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and your body metabolizes
and absorbs oxygen.

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Since you're
breathing less nitrogen,

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you can stay down longer
all else being the same,

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compared to the same
dive using regular air.

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How much more no stop bottom time
you get depends upon your depth

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and the amount of oxygen
in your enriched air blend.

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In the 15 metre/50 foot
to 27 metre/90 foot range,

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the additional time can be substantial,
especially on repetitive dives.

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When you use enriched air with
an enriched air dive computer,

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your no stop time is so long that
you're more likely to be limited

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by your gas consumption than by
reaching a no decompression limit.

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Sometimes divers wonder whether
the no stop limits for enriched air

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are as reliable as for air,
and the answer is ''yes.''

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Decades of tests and field experience
with hundreds of thousands of dives

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by military, scientific
and recreational divers

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has established an excellent safety
record for no stop diving with enriched air.

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Sometimes divers wonder
whether enriched air

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might have a safety advantage
over air, or if it causes less narcosis.

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Diving well within
air no stop limits,

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there's probably no meaningful
safety gain by using enriched air nitrox.

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And, since oxygen has similar
narcotic properties to nitrogen,

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plan your dive taking narcosis into
account, just as you would with air.

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Enriched air does have five
considerations you don't have

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diving with air within
recreational limits.

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First, there's a potential
for oxygen toxicity.

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This is the most serious of the potential
hazards unique to enriched air diving.

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Second, you'll have a few
special equipment considerations.

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Third, enriched air isn't
as readily available as air,

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and fourth, enriched air requires
special blending and handling protocols.

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Finally, you'll find that
planning an enriched air dive

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takes a few more steps than an air dive
and there's a bit more error potential -

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though it's not
particularly difficult.

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The primary concern about
enriched air and your equipment

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is the high oxygen
content in enriched air.

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In the presence
of high oxygen,

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many materials will burn or
explode that wouldn't otherwise.

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High oxygen can also make equipment
deteriorate more rapidly over time.

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However, with enriched air that
has no more than 40 percent oxygen,

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the community guideline is that
you can use the same regulator, BCD

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and other equipment that you
use for air except for your cylinder.

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We'll look at
cylinders in a moment.

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However, manufacturers, local laws
and regulations and local practices

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may require special equipment
modifications for enriched air.

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A few manufacturers say not to use
their equipment with enriched air at all.

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Follow the requirements that apply
to your gear and your local area.

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Unlike your
other equipment,

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enriched air diving requires a
dedicated cylinder, for two reasons.

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The first is that is
must be clearly marked

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so no one accidentally dives
with enriched air thinking it's air.

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The second is that one
method of making enriched air

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involves putting pure
oxygen in the cylinder.

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For safety, a cylinder used
for blending gases this way

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needs to be specially
cleaned and lubricated -

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even if the final blend will
have less than 40 percent oxygen.

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Typically, an enriched air cylinder has a
distinct color or band to clearly identify it.

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This type is
the most common,

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but local regulations may
stipulate other color coding.

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The cylinder will have a contents sticker
or tag shows what enriched air is in it,

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a decal showing whether the cylinder
meets oxygen service requirements,

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and an inspection sticker like you
find on any other scuba cylinder.

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Filling your cylinder
has some concerns, too.

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The first is that high oxygen content
can present a fire/explosion hazard,

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and the second is
that to dive it safely,

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you need to be certain of the percentage
of oxygen in your enriched air.

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To manage these concerns, always
have enriched cylinders filled

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at a proper enriched air station
by a qualified enriched air blender.

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Certified gas blenders
have the special training

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and blending equipment necessary to
avoid possible hazards related to oxygen.

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And, they know how to blend accurately
so you get the enriched air mix you want.

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This is especially important
for enriched air cylinders

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that must meet oxygen service
requirements for blending.

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Conventional air fill systems
may contaminate a cylinder

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with trace lubricants that are harmless
with air, but create a fire risk with oxygen.

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All gases put in the cylinder, including
air, must be oxygen compatible.

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If an oxygen service rated
cylinder is accidentally filled

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from any source that doesn't
provide oxygen compatible gas or air,

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you need to have it reserviced before
it can come in contact with any gas

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with more than
40 percent oxygen.

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This is why you would never
put pure oxygen in a scuba cylinder

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and have it filled from
a conventional air station

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in an attempt to
make enriched air.

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Doing so poses a significant
fire or explosion risk.

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Reputable blenders are trained and
certified to avoid these problems.

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Look for the DSAT
Gas Blender certification

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or other credentials showing
training in gas blending.

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If you're interested in learning
to blend enriched air nitrox,

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ask your PADI
Instructor, Dive Center

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or Resort about the
DSAT Gas Blender course.

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Diving air within recreational limits,
your oxygen exposure isn't an issue.

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With enriched air's
higher content, it is.

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As an enriched air diver, you need
to stay within accepted oxygen limits

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and track your exposure,
much as you do with nitrogen.

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You measure your oxygen exposure
based on the oxygen partial pressure,

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which refers to the pressure exerted
by just the oxygen in your enriched air.

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Find this by multiplying
the oxygen percentage

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times the absolute pressure
at depth in atmosphere or bar.

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For example, suppose you dive to 10
metres or 33 feet using Enriched Air 40.

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As you recall, at 10 metres/33 feet,
the pressure is two atmospheres,

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one of air and
one of water.

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40 percent oxygen
times 2 atmospheres

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= 0.80 atmospheres of
oxygen partial pressure.

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When working with percents,
remember to use the decimal form,

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.40 in this example.

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Oxygen partial pressure will vary
with your depth and the blend.

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Your oxygen partial pressure
is .80 atmospheres absolute

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at 10 metres/33 feet,
but with enriched air 36,

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you reach .80 atmospheres
absolute at 12 metres/40 feet.

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Your oxygen
exposure is the same.

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Oxygen limits are therefore
independent of depth.

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The maximum oxygen partial
pressure is 1.4 atmospheres absolute.

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You will learn to plan your dives so you
don't exceed the blend's maximum depth,

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which is the depth it reaches
1.4 oxygen partial pressure.

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This is the accepted dive
community standard,

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with a partial pressure of
1.6 atmospheres absolute

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used as a contingency
depth for planning purposes.

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You want to dive conservatively,
well within the limits.

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Planning your dive so you remain
well above the maximum depth

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where your blend reaches
1.4 Oxygen partial pressure

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gives you room for error
and an added margin of safety.

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By staying
well within limits,

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you minimize the most serious risk in
enriched air diving, oxygen toxicity.

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Exceeding 1.4 atmospheres absolute

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partial pressure can cause
central nervous system toxicity,

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which can manifest
itself as a convulsion.

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While a convulsion isn't
usually directly harmful,

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underwater a diver is almost certain
to lose his regulator and drown.

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Warning signs and symptoms may
precede a convulsion, but usually they don't.

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If they do occur, they
include visual disturbances,

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ears ringing,
nausea,

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twitching or
muscle spasms -
especially in the face,

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irritability
or anxiety,

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and
dizziness.

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You can
remember these

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by remembering
VENTID.

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If you
experience any of
these symptoms,

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ascend and
end the dive
immediately.

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Heavy exertion, some drugs
and carbon dioxide retention

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may predispose a
diver to oxygen toxicity.

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Avoid overexertion
and breathe normally.

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Consult a physician
knowledgeable in diving

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with respect to prescription
medications before diving with them.

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Within the limits, enriched air
diving has an excellent safety record -

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but ignoring the limits
can be life threatening.

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Remember, it's very easy
to manage oxygen exposure

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simply by staying well
within accepted limits.

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In Section Two you'll learn more
about tracking oxygen exposure,

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but for now, realize that not exceeding
an oxygen partial pressure of 1.4

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is the most important
precaution you need to follow.

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By now you realize
that to plan your dives,

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you need to know the oxygen
percentage of the enriched air you use.

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You use your oxygen percentage
to set enriched air dive computers,

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to determine your no stop limits and
to manage your oxygen exposure.

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Gas blenders analyze enriched air after
mixing it using an oxygen analyzer.

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Nonetheless, you personally analyze
the gas yourself, or in some cases,

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you watch someone analyze it while
you personally confirm the analysis.

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Do not dive an enriched air cylinder unless
you've personally verified the contents.

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There are no exceptions.

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Although errors are rare, this
is an important double check

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of the initial analysis and that
the cylinder's been marked correctly.

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Never forget that
if there's an error,

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the person who can get
hurt is the diver - you.

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Just as important, once
you confirm the gas analysis,

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keep your cylinder somewhere
that it won't accidentally be used

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by someone else or create any
question about what's in it.

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If there's ever a
doubt, reanalyze it.

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It's a good practice to re-analyze
just before a dive in any case.

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Let's review the procedures
for analyzing enriched air.

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You can use one of the many
analyzers currently available to divers.

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Begin by turning it
on and calibrating it.

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You usually do this by flowing
air through the analyzer

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with a flow restrictor or
other flow control device.

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Some of these connect to your
regulator's low pressure hose.

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Others attach
directly to the valve.

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Use a slow controlled flow
and set the analyzer for air -

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usually 20.8 to 21 percent oxygen,
depending on the analyzer.

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After calibrating,
leave the analyzer on

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and flow enriched air through
it at about the same rate.

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Allow the reading to stabilize and read
the oxygen percentage off the display.

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You can calibrate some analyzers
using the air in the room,

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but don't do this
in high humidity

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or when you've been
analyzing a lot of cylinders

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because these can
affect the calibration.

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Your best bet is to calibrate
with a cylinder of compressed air.

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Analyzers are reliable, but
if there's ever any doubt,

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compare the one you're
using with another.

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Your readings should be within
less than a percent of each other.

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After analyzing, compare your analysis
with the cylinder contents sticker or tag.

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Minor variations between the
blender's analysis and yours are normal.

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But, if you've already
planned your dive

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and the blend is off by
more than one percent,

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you need to recalculate your maximum
depth and no stop limits if using tables,

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or reset an enriched air dive
computer if you already set it.

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00:20:05,995 --> 00:20:10,091
Most enriched air computers and
tables use one percent increments,

230
00:20:10,165 --> 00:20:14,124
so round fractions to
the closest whole percent.

231
00:20:14,236 --> 00:20:17,137
In this case,
for instance,

232
00:20:17,206 --> 00:20:23,111
you'd set your enriched air
dive computer for 36 percent.

233
00:20:23,479 --> 00:20:25,777
After confirming
the oxygen content,

234
00:20:25,848 --> 00:20:29,511
check that the maximum
depth for the blend is correct

235
00:20:29,585 --> 00:20:31,917
- or fill it in if it's blank -

236
00:20:31,987 --> 00:20:38,586
and that your
name's on the cylinder.

237
00:20:39,295 --> 00:20:43,493
You'll finish by signing the dive
operation's enriched air fill log,

238
00:20:43,565 --> 00:20:48,400
which usually lists the cylinder
number, the gas blend,

239
00:20:48,470 --> 00:20:51,132
the maximum depth

240
00:20:51,206 --> 00:20:53,538
and your name.

241
00:20:53,642 --> 00:20:57,271
If the operation brings the
cylinders to you at the dive site,

242
00:20:57,346 --> 00:21:00,406
they'll bring a log
sheet with them.

243
00:21:01,517 --> 00:21:06,784
After your dive, leave the
contents sticker or tag in place.

244
00:21:06,889 --> 00:21:10,950
The blender uses it to confirm
the residual blend inside.

245
00:21:11,060 --> 00:21:16,498
It's okay to write ''used''
or ''empty'' on it, though.

246
00:21:29,044 --> 00:21:32,275
Although it's important to
understand table use with enriched air,

247
00:21:32,348 --> 00:21:37,911
using enriched air dive
computers is much more popular.

248
00:21:38,854 --> 00:21:44,019
Computers maximize your no stop time,
especially when multilevel diving,

249
00:21:44,093 --> 00:21:49,224
and most will warn you if you
accidentally exceed the maximum

250
00:21:49,298 --> 00:21:52,165
or contingency depth
for your gas blend.

251
00:21:53,268 --> 00:21:58,331
Most also calculate your oxygen
exposure as well as no stop time

252
00:21:58,407 --> 00:22:03,709
and warn you if you
near the limits of either.

253
00:22:04,246 --> 00:22:07,875
Different models vary in how
you set them, but with most,

254
00:22:07,950 --> 00:22:12,216
you enter a set mode and then scroll
through the oxygen percentage

255
00:22:12,287 --> 00:22:16,348
until you find the blend
you're using, then lock it in.

256
00:22:16,458 --> 00:22:21,953
If you forget to do this, most
computers will go into an error mode.

257
00:22:22,064 --> 00:22:25,864
See the manufacturer instructions for
the particular computer you're using,

258
00:22:25,934 --> 00:22:28,698
or ask
your instructor.

259
00:22:30,572 --> 00:22:33,405
When diving with an
enriched air computer,

260
00:22:33,475 --> 00:22:37,070
know the blend's maximum
depth and stay shallower

261
00:22:37,146 --> 00:22:39,740
by following
the depth display.

262
00:22:39,848 --> 00:22:45,787
Use the computer warning
as a secondary alert.

263
00:22:45,921 --> 00:22:50,585
Dive conservatively, well within
both the computer's no decompression

264
00:22:50,659 --> 00:22:54,925
and oxygen limits,
and make safety stops.

265
00:22:55,364 --> 00:22:58,697
It's a good idea to back
up your dive computer

266
00:22:58,767 --> 00:23:03,602
with the tables you'll learn
to use in this course,

267
00:23:05,107 --> 00:23:09,066
and of course, each diver
needs a personal computer.

268
00:23:09,178 --> 00:23:12,614
Don't try to
dive sharing one.

269
00:23:30,632 --> 00:23:35,729
There are two considerations about
enriched air nitrox and emergencies:

270
00:23:35,871 --> 00:23:39,739
what to do if a diver
convulses underwater,

271
00:23:39,842 --> 00:23:46,077
and what to do for suspected decompression
illness for an enriched air diver.

272
00:23:46,715 --> 00:23:50,913
Although it's highly unlikely when
staying within accepted oxygen limits,

273
00:23:50,986 --> 00:23:53,955
if a diver were to
convulse underwater,

274
00:23:54,022 --> 00:23:59,289
handle the emergency just as you
would any unresponsive diver accident.

275
00:24:01,263 --> 00:24:07,862
Hold the diver's mouthpiece in if it's in
place and bring the diver to the surface.

276
00:24:14,209 --> 00:24:22,082
Establish buoyancy
and check for breathing.

277
00:24:22,351 --> 00:24:25,912
Call for assistance and
get the victim to safety,

278
00:24:25,988 --> 00:24:28,855
providing rescue
breaths as needed.

279
00:24:28,957 --> 00:24:33,121
Once out of the water, continue to
monitor breathing and circulation,

280
00:24:33,195 --> 00:24:36,756
providing CPR and
rescue breaths as needed

281
00:24:36,832 --> 00:24:40,324
while waiting for emergency
medical care to arrive.

282
00:24:40,435 --> 00:24:44,872
Some experts suggest holding
the diver's mouthpiece in

283
00:24:44,940 --> 00:24:48,637
and waiting for the convulsion
to subside before ascending.

284
00:24:48,744 --> 00:24:55,411
But, the primary concern is
getting the diver to the surface.

285
00:24:56,018 --> 00:25:00,751
If an enriched air diver is suspected
of having decompression illness,

286
00:25:00,822 --> 00:25:04,815
provide first aid
- including emergency oxygen -

287
00:25:04,893 --> 00:25:07,453
just as you would
for an air diver.

288
00:25:07,563 --> 00:25:12,500
The oxygen exposure during
the dive is not a concern.

289
00:25:13,368 --> 00:25:16,030
When there's enriched
air at a dive site,

290
00:25:16,104 --> 00:25:21,599
you can provide it to a breathing diver if
you run out of oxygen before help arrives.

291
00:25:21,710 --> 00:25:25,043
It may not be as
helpful as pure oxygen,

292
00:25:25,113 --> 00:25:29,516
but it may help and
certainly won't hurt.

293
00:25:30,385 --> 00:25:33,752
You can learn more about preventing
and managing diver emergencies

294
00:25:33,822 --> 00:25:35,653
in the PADI
Rescue Diver course

295
00:25:35,724 --> 00:25:41,685
and in the Emergency First Response,
Primary and Secondary Care courses.

296
00:25:41,763 --> 00:25:46,530
Ask your instructor about these
programs if you've yet to complete them.

297
00:26:02,884 --> 00:26:05,853
Section Two of the PADI
Enriched Air Diver course

298
00:26:05,921 --> 00:26:12,383
focuses on planning enriched air dives
with the RDP, the Enriched Air RDPs

299
00:26:12,461 --> 00:26:17,057
and the Equivalent Air Depth
and Oxygen Exposure Table.

300
00:26:17,165 --> 00:26:21,864
You'll also learn a bit about using blends
with more than 40 percent oxygen,

301
00:26:21,937 --> 00:26:29,503
and an overview of technical diving
and how it relates to enriched air diving.

302
00:26:41,023 --> 00:26:45,426
Let's begin with how you'll use
the standard RDP table for air

303
00:26:45,494 --> 00:26:49,157
with enriched air to find
your no decompression limits,

304
00:26:49,231 --> 00:26:54,328
repetitive groups and adjusted
no decompression limits.

305
00:26:55,871 --> 00:26:59,637
Before we do, though, let's
look at how this video presentation

306
00:26:59,708 --> 00:27:03,974
helps you learn
to use these tables.

307
00:27:04,613 --> 00:27:08,049
Each section covers concepts
and general table use,

308
00:27:08,116 --> 00:27:11,517
but without
detailed examples.

309
00:27:11,887 --> 00:27:16,915
Most people find specific table problems
difficult and confusing to follow on video,

310
00:27:17,025 --> 00:27:20,586
leading to frustration
rather than learning.

311
00:27:20,962 --> 00:27:23,795
So, watch to learn
the general concepts,

312
00:27:23,899 --> 00:27:27,960
then read your PADI
Enriched Air Diver Manual.

313
00:27:28,070 --> 00:27:31,631
The manual has specific examples
that you can easily work through

314
00:27:31,707 --> 00:27:35,143
and follow at
your own pace.

315
00:27:35,711 --> 00:27:39,374
Don't worry about memorizing
everything while watching the video.

316
00:27:39,481 --> 00:27:44,145
That's not the purpose.

317
00:27:44,953 --> 00:27:50,016
Since the air RDP is based on breathing
with air, to use it with enriched air

318
00:27:50,092 --> 00:27:56,361
you will use an adjusted depth that
accounts for your reduced depth.

319
00:27:57,165 --> 00:28:01,226
This is called an EAD
- Equivalent Air Depth -

320
00:28:01,303 --> 00:28:04,101
which is shallower
than the actual depth.

321
00:28:04,206 --> 00:28:11,908
You use the EAD to plan your
dive in place of the actual depth.

322
00:28:12,314 --> 00:28:17,251
You find EADs for Enriched Air
Blends with 30 to 40 percent oxygen

323
00:28:17,319 --> 00:28:20,311
on the Equivalent
Air Depth Table.

324
00:28:20,422 --> 00:28:24,415
You find your planned actual
depth in a column on the left,

325
00:28:24,493 --> 00:28:28,725
then find the EAD for it
under the blend you're using.

326
00:28:31,967 --> 00:28:38,805
Use the EAD to find your no decompression
limit on Table One of the RDP,

327
00:28:38,874 --> 00:28:43,106
and to find your repetitive
group after the dive.

328
00:28:43,178 --> 00:28:48,844
Once you have your EAD, you simply
use it in place of the actual depth.

329
00:28:50,085 --> 00:28:54,044
For a repetitive dive,
continue through Table 2

330
00:28:54,122 --> 00:28:57,785
to find your new Pressure
Group after the surface interval

331
00:28:57,859 --> 00:28:59,349
just as you've
already learned.

332
00:29:00,996 --> 00:29:04,295
When you get to
Table 3, use the EAD

333
00:29:04,366 --> 00:29:07,096
of the blend you'll make the
repetitive dive with for planning.

334
00:29:10,005 --> 00:29:13,202
Use the Equivalent Air Depth Table

335
00:29:13,275 --> 00:29:18,144
to find the EAD for repetitive dive's
planned depth and blend.

336
00:29:18,513 --> 00:29:23,450
On Table 3, use the EAD to find
your adjusted no decompression limit

337
00:29:23,518 --> 00:29:26,316
and residual
nitrogen time.

338
00:29:28,757 --> 00:29:33,660
Remember that ADJUSTED NO DECOMPRESSION
LIMITS AND RESIDUAL NITROGEN TIMES

339
00:29:33,728 --> 00:29:36,959
ARE ALWAYS BASED ON THE
BLEND YOU'RE SWITCHING TO.

340
00:29:37,365 --> 00:29:40,994
After running through the examples
in the Enriched Air Diver Manual,

341
00:29:41,069 --> 00:29:46,473
you'll find this fairly easy because you're
using the RDP the same way you always have,

342
00:29:46,541 --> 00:29:52,104
except you use EADs in place
of the actual depth for planning.

343
00:29:53,048 --> 00:29:58,384
But to make things even easier,
there are two special RDPs,

344
00:29:58,453 --> 00:30:03,356
one for enriched air 32
and one for enriched air 36,

345
00:30:03,425 --> 00:30:06,121
which are the two
most popular blends.

346
00:30:09,264 --> 00:30:11,994
You don't use
EADs with these.

347
00:30:12,067 --> 00:30:16,333
Instead, you use them
much like the air RDP,

348
00:30:16,404 --> 00:30:22,434
except that you must be diving with enriched
air 32 or 36 as appropriate, of course.

349
00:30:23,612 --> 00:30:28,515
The Enriched Air RDP pressure groups
are interchangeable with the air RDP's,

350
00:30:28,583 --> 00:30:32,417
so you can switch to
the air RDP with EADs,

351
00:30:32,487 --> 00:30:39,120
or from one Enriched Air RDP to the other,
if you switch blends for a repetitive dive.

352
00:30:40,228 --> 00:30:43,459
Remember that you
switch as you enter Table 3

353
00:30:43,531 --> 00:30:49,561
and use the EAD or Enriched Air RDP
for the blend you are switching to.

354
00:30:50,105 --> 00:30:53,871
Go through the examples in the
PADI Enriched Air Diver Manual

355
00:30:53,942 --> 00:30:56,035
and you'll find
this straightforward.

356
00:31:11,126 --> 00:31:15,062
Earlier you learned that to
control your oxygen exposure,

357
00:31:15,130 --> 00:31:18,588
you need to plan your dive so you
don't exceed the depth at which

358
00:31:18,667 --> 00:31:22,899
the blend you're using reaches
1.4 oxygen partial pressure.

359
00:31:23,672 --> 00:31:26,835
The horizontal line on
Equivalent Air Depth Table

360
00:31:26,908 --> 00:31:30,571
corresponds with the
maximum depth for each blend.

361
00:31:30,645 --> 00:31:34,081
You find the EAD
immediately above the line

362
00:31:34,149 --> 00:31:37,744
and the corresponding actual
depth on the left side of the table.

363
00:31:37,819 --> 00:31:42,256
This is the maximum
depth with that blend.

364
00:31:42,324 --> 00:31:50,231
Below the line, find the last EAD listed and
the corresponding actual depth on the left.

365
00:31:50,332 --> 00:31:54,666
This is the contingency depth,
for emergency planning only.

366
00:31:54,769 --> 00:32:00,332
The Equivalent Air Depth Table also
shows you the oxygen partial pressure

367
00:32:00,408 --> 00:32:02,171
for each
depth and blend.

368
00:32:02,243 --> 00:32:10,048
Notice that the oxygen partial pressure for
the maximum depth is near, but not over, 1.4,

369
00:32:10,118 --> 00:32:16,421
and for the contingency
depth, near but not over 1.6.

370
00:32:18,460 --> 00:32:21,258
You will also use the
oxygen partial pressure

371
00:32:21,329 --> 00:32:25,459
to keep your oxygen exposure
within 24 hours within limits.

372
00:32:25,533 --> 00:32:31,233
To do this, you find the oxygen partial
pressure for the dive depth and blend,

373
00:32:31,306 --> 00:32:33,740
the same way
you find the EAD.

374
00:32:33,875 --> 00:32:39,745
Take the oxygen partial pressure to the
Oxygen Exposure Table and find it on the top.

375
00:32:39,848 --> 00:32:45,252
Round to the next higher one if
the exact partial pressure isn't listed.

376
00:32:47,222 --> 00:32:51,386
Under the oxygen partial
pressure, find your dive time,

377
00:32:51,459 --> 00:32:55,759
again rounding up to the next greater
time if the exact time isn't there.

378
00:32:55,830 --> 00:33:00,563
Then, find the oxygen
exposure percent on the right.

379
00:33:01,236 --> 00:33:06,435
This is how much of your allowable
exposure you've used for that dive.

380
00:33:06,541 --> 00:33:11,535
When making multiple dives,
you add the exposures for each dive,

381
00:33:11,613 --> 00:33:16,983
making sure you don't exceed
100 percent in 24 hours.

382
00:33:20,488 --> 00:33:23,855
In practice, you'll find
you can dive quite a bit

383
00:33:23,925 --> 00:33:26,758
and still be well within
oxygen exposure limits,

384
00:33:26,828 --> 00:33:34,360
especially if you keep your oxygen
partial pressure well below 1.4.

385
00:33:34,636 --> 00:33:39,369
Being conservative, it's recommended
you stay within 90 percent,

386
00:33:38,440 --> 00:33:45,869
and if you exceed 50 percent,
allow at least one hour between dives.

387
00:33:46,014 --> 00:33:49,506
If you accidentally exceed
1.6 atmospheres absolute,

388
00:33:49,584 --> 00:33:52,280
your oxygen
exposure is 100 percent

389
00:33:52,353 --> 00:33:56,915
and you should not
dive for at least 12 hours.

390
00:33:57,425 --> 00:34:02,522
In planning your dives, use
the Equivalent Air Depth Table,

391
00:34:01,596 --> 00:34:07,228
RDPs and Oxygen Exposure Table to
determine your allowable no stop time

392
00:34:07,302 --> 00:34:11,295
and your allowable
oxygen exposure remaining.

393
00:34:11,406 --> 00:34:15,866
Remember, your allowable dive
time is always whichever is shorter.

394
00:34:15,944 --> 00:34:19,402
You'll find this simple
after some practice

395
00:34:19,481 --> 00:34:23,815
with the examples in the PADI
Enriched Air Diver Manual.

396
00:34:23,985 --> 00:34:32,484
And, use the manual if you get
rusty and need to review table use.

397
00:34:45,740 --> 00:34:50,768
As a recreational diver, most of
your enriched air nitrox dives

398
00:34:49,844 --> 00:34:54,144
will be made with
30 to 40 percent oxygen.

399
00:34:53,248 --> 00:34:57,412
Recreational divers seldom use
blends with higher oxygen content.

400
00:34:57,619 --> 00:35:03,956
But an exception is when diving with
recreational semiclosed circuit rebreathers.

401
00:35:04,058 --> 00:35:09,360
Semiclosed circuit rebreathers
recycle part of each breath,

402
00:35:09,430 --> 00:35:14,026
which means you consume some
of the oxygen with each cycle.

403
00:35:14,135 --> 00:35:20,597
So, these units often require enriched
air with more than 40 percent oxygen.

404
00:35:21,543 --> 00:35:23,807
The primary
equipment concern

405
00:35:23,878 --> 00:35:26,972
is that with blends that have
more than 40 percent oxygen,

406
00:35:27,048 --> 00:35:30,848
all equipment in contact with
the gas, including the regulator,

407
00:35:30,919 --> 00:35:36,084
must meet oxygen
service standards.

408
00:35:36,824 --> 00:35:41,852
The Equivalent Air Depth Table
doesn't list information for these blends,

409
00:35:41,930 --> 00:35:45,991
so you'll use a few simple
formulas to determine EADs,

410
00:35:46,067 --> 00:35:50,504
oxygen partial pressure
and the maximum depths.

411
00:35:50,605 --> 00:35:55,702
The PADI Enriched Air Diver
Manual covers this in detail.

412
00:35:56,678 --> 00:35:59,044
If you're using an
enriched air dive computer,

413
00:35:59,113 --> 00:36:05,018
you'll need one that you can set
for blends higher than 40 percent.

414
00:36:08,990 --> 00:36:12,357
See your PADI Instructor if you're
interested in learning more about

415
00:36:12,427 --> 00:36:15,726
semiclosed circuit
recreational rebreathers.

416
00:36:32,180 --> 00:36:39,780
Both recreational divers and technical
divers benefit from enriched air nitrox.

417
00:36:38,886 --> 00:36:43,721
While learning to dive with enriched air is
a necessary step toward become a tec diver,

418
00:36:43,791 --> 00:36:48,694
the PADI Enriched Air Diver
course is not a tec diving course.

419
00:36:48,863 --> 00:36:52,560
Tec diving involves using
extensive equipment and procedures

420
00:36:52,634 --> 00:36:57,765
to exceed the established
limits of recreational diving.

421
00:36:57,972 --> 00:37:02,466
Tec divers dive deeper
than 40 metres/130 feet.

422
00:37:02,577 --> 00:37:06,013
Their dives may require
staged decompression

423
00:37:06,080 --> 00:37:12,041
and using two or more
gas mixes on a single dive.

424
00:37:12,387 --> 00:37:18,690
As a PADI Enriched Air Diver, you qualify
to use enriched air to extend your dive time.

425
00:37:18,860 --> 00:37:24,821
This isn't tec diving,
though it's certainly a benefit.

426
00:37:25,466 --> 00:37:29,630
Realize that attempting technical diving
without the proper equipment and training

427
00:37:29,704 --> 00:37:37,167
is very hazardous, and accounts for a
disproportionate number of diving accidents.

428
00:37:37,578 --> 00:37:41,810
If you're interested in tec diving, ask
your instructor or dive operation about

429
00:37:41,883 --> 00:37:47,378
the DSAT Tec Deep Diver
course and other TecRec courses.

430
00:37:47,488 --> 00:37:51,356
TecRec courses are regarded
as the most instructionally solid,

431
00:37:51,426 --> 00:37:54,987
top tec diver
training available.

432
00:37:57,498 --> 00:38:01,696
Becoming certified as a PADI
Enriched Air Diver adds a new skill

433
00:38:02,036 --> 00:38:05,563
that expands your underwater
dive time opportunities.

434
00:38:05,673 --> 00:38:09,336
When you're newly certified, you'll
probably want to use your new skills

435
00:38:09,410 --> 00:38:12,436
by diving with
enriched air a lot.

436
00:38:12,547 --> 00:38:18,349
With experience, though, you'll come to
realize you don't need it on every dive.

437
00:38:18,753 --> 00:38:22,587
Like diving with a dry suit,
it's a wonderful tool,

438
00:38:22,657 --> 00:38:25,717
but not one you need
for every dive at every site.

439
00:38:25,793 --> 00:38:28,853
When you reach this point,
you'll be at the stage

440
00:38:28,930 --> 00:38:34,732
where you get the most practical
use from diving enriched air nitrox.