Dive Tables and Dive Computers
63
play if a diver is ascending too fast. Additional bells and
whistles may include temperature, scrolling of maximum
dive times for the next dive or actual pre-dive
planning software for repetitive dives, and dive recall
display of not just a few but many previous dives and
surface intervals. Many computers will allow you to
download your dives to a logbook program on a computer.
(General experience using computers prompts the
warning: Keep a backup!)
In addition, with a nitrox-capable computer you
can set the oxygen percentage of your breathing gas on
each dive. The computer then calculates nitrogen
absorption for your dive based on the oxygen level that
you have “dialed in.” Nitrox computers will also track
single-dive and 24-hour oxygen exposure limits. If you
use a nitrox computer, read the manufacturer’s instructions
carefully. Some computers will revert to a default
value of air or to an extremely conservative value if you
do not dive with them within a certain time of setting
the mixture. Also, different manufacturers use different
gas absorption models, and dive computer brands and
models vary from less to more conservative–in addition
to variations in their display and download features. As
with acquiring any diving equipment, you should establish
your own personal needs and look into the range of
computers available before buying.
As a nitrox diver, you have two basic options. With a
nitrox-capable computer, you can set the computer to
exactly model the theoretical nitrogen loading and offgassing
for your dives. On the other hand, many divers
opt for an air computer, which will present an automatic
safety margin when diving with nitrox. Another
option is to acquire an enriched air nitrox computer and
leave it set at 21% oxygen unless you want to use the
advantages of nitrox on given dives.
You now have enough information to use oxygenenriched
air for safe diving and dive planning. In the
final chapters of this book, you will learn precautions
that must be exercised when handling oxygen at high
partial pressures, how diving equipment is cleaned and
serviced for exposure to oxygen, how nitrox is prepared,
and your responsibility for gas analysis and other
unique aspects of nitrox use.