Myth 5: “If you dive with nitrox you won’t get
narcosis.”
It is easy to assume that the reduced nitrogen in
nitrox should reduce narcosis just as it provides
advantages in other areas. The fact is that narcosis
involves many factors, some of which are psychological.
Evidence on nitrox and narcosis is sparse, but it is
best to regard the narcotic potency of nitrox as the
same as that of air. While it has been theorized that
unmetabolized oxygen may be as narcotic as nitrogen,
recreational nitrox divers do not subject themselves to
oxygen pressures where this could be a factor. In order
to reduce narcosis on deep dives, technical divers use
trimix to lower both the nitrogen and the oxygen
content of their breathing gas.
Myth 6: “It is hard to dive with nitrox.”
This book will help you to learn the proper planning
and procedures for conducting dives with enriched
air nitrox. Most of the procedures are simple, and where
there are calculations involved, the formulas are usually
backed up with tables where you can look up the necessary
derived information. Using nitrox involves an
understanding of partial pressures and oxygen limits,
somewhat more advance planning and preparation than
air diving, and an acceptance of your added responsibility
for safe diving. But the training to become a nitrox
diver is far less than the initial training that prepared
you to be a scuba diver. Once you are in the water, the
rule of nitrox diving is the same as any other diving:
Plan your dive, and dive your plan.
TERMINOLOGY
You will meet a number of new or unfamiliar terms
in this book. Some of them, such as “partial pressure,”
you encountered in your first scuba course, but you may
have not used or seen them since then. Important terms
will be emphasized in bold type at least the first time
they are used in this book and defined in context when
necessary. A glossary is included at the end of the book
Chapter 1- Introduction
where you can look up definitions of unfamiliar terms.
Enriched air nitrox, nitrox, oxygen-enriched air,
and EANx are used interchangeably throughout this
text. Where applicable, the “x” may be replaced by the
oxygen percentage (e.g. EAN36). In your reading elsewhere,
you will also see references to NOAA Nitrox I and
NOAA Nitrox II. These terms refer to EAN32 and EAN36
respectively, and NOAA is currently trying to change its
terminology to NN32 and NN36.
The amount of a component gas in a mixture may
be expressed as a percentage or a fraction. A percentage
compares the quantity of the component gas to a total of
100; a fraction compares it to one. EAN36 can be said to
be 36% oxygen and 64% nitrogen, or it can be said that
the fraction of oxygen is 0.36 and that of nitrogen is
0.64. In formulas and calculations, the gas component
is always expressed as a fraction.
It is best to not use terminology in which the
components are unspecified. Terms like “60-40 mix” are
ambiguous. This is particularly so because in some usages
it is customary to state the oxygen first, and in others to
state the inert gas first. If the meaning is not specified,
either number could refer to the oxygen content, and
getting it wrong could have disastrous results.
Welcome to the world of nitrox diving! Dive safely.
This book will give you tools and techniques to extend
your enjoyment of the underwater world.
Introduction
11