cylinder, allow the analyzer system to depressurize or
depressurize it manually, remove the setup from the air
cylinder, and reattach it to your nitrox cylinder. Then,
turn on the valve of the nitrox cylinder. You may need to
be expeditious with this switch, as most analyzers will
turn themselves off after a certain time of no use. Check
the flow rate if it is adjustable and set it to the same as it
was for your air analysis. Allow a minute for the reading
to stabilize and then take a reading of the oxygen fraction
or percentage of your mix. Record this information
on your cylinder contents label.
CYLINDER LABELING
Every oxygen-enriched air cylinder must be properly
labeled with its contents and other necessary information.
The label should be prepared immediately after
the contents are analyzed in order to avoid forgetful
errors. The cylinder label may be a commercially prepared
decal or tag that can be written on with a waterproof
marker and subsequently erased or wiped off with
alcohol and reused. Or, a label can be made using an
indelible marker on tape that will be removed before the
next refill. The data on the cylinder label should
include: fill date, oxygen percentage, maximum operating
depth, cylinder pressure, and the name of the analyzer/
end-user. An evolving practice is to add a second
label mounted vertically on the cylinder body and
marked with maximum operating depth in numbers
three inches high (for example, using house-number
decals). This MOD label is positioned so that it is unobstructed
and can be easily read by a dive partner who is
swimming next to the user.
FILLING OUT THE LOGBOOK
Once you have analyzed your cylinder and labeled
it, you will be asked to complete a permanent Fill
Station Log and sign-off that you have received the
cylinder. This logbook is kept by the facility that filled
your cylinder. In the logbook, you will enter your name,
the date, your certification, the cylinder’s serial number,
the cylinder pressure, the oxygen percentage of the mix,
and the maximum operating depth. You will also sign
the logbook entry.
The cylinder log is used to keep track of all nitrox
cylinders that leave the facility. It also verifies, by your
signature, that you either analyzed the contents or
watched as a blending technician analyzed them for
you, and that you knew the particulars of the fill and its
limits when you received the cylinder.
And so, at last, you have it all together, and you are
ready to enjoy the world of nitrox diving. Armed with
your cylinder of enriched air nitrox–perhaps blended to
your personal specifications, your knowledge of the risks,
limits, and advantages of the gods’ ambrosia/devil’s gas
that you are about to use, an appropriate dive plan, and
a compatible dive partner, you head off to the dive site.
There you and your partner assemble and don your
equipment, rehearse and review your dive plan (including
a review of your MOD), mutually check each other’s
gear, and begin your dive. And, once you make your
descent, it really is “just like breathing air.”
Safe diving.
NAUI Nitrox Diver
82 Knowing What You Breathe
FIGURE 7-4: NAUI EANX CYLINDER CONTENTS LABEL