2-16 Change A
U.S. Navy Diving ManualVolume 1
Hydrogen. Hydrogen (H2) is diatomic, colorless, odorless, and tasteless, and is so
active that it is rarely found in a free state on earth. It is, however, the most abun-
dant element in the visible universe. The sun and stars are almost pure hydrogen.
Pure hydrogen is violently explosive when mixed with air in proportions that
include a presence of more than 5.3 percent oxygen. Hydrogen has been used in
diving (replacing nitrogen for the same reasons as helium) but the hazards have
limited this to little more than experimentation.
Neon. Neon (Ne) is inert, monatomic, colorless, odorless, and tasteless, and is
found in minute quantities in the atmosphere. It is a heavy gas and does not exhibit
the narcotic properties of nitrogen when used as a breathing medium. Because it
does not cause the speech distortion problem associated with helium and has supe-
rior thermal insulating properties, it has been the subject of some experimental
Carbon Dioxide. Carbon dioxide (CO2) is colorless, odorless, and tasteless when
found in small percentages in the air. In greater concentrations it has an acid taste
and odor. Carbon dioxide is a natural by-product of animal and human respiration,
and is formed by the oxidation of carbon in food to produce energy. For divers, the
two major concerns with carbon dioxide are control of the quantity in the
breathing supply and removal of the exhaust after breathing. Carbon dioxide can
cause unconsciousness when breathed at increased partial pressure. In high
concentrations the gas can be extremely toxic. In the case of closed and semi-
closed breathing apparatus, the removal of excess carbon dioxide generated by
breathing is essential to safety.
Carbon Monoxide. Carbon monoxide (CO) is a colorless, odorless, tasteless, and
poisonous gas whose presence is difficult to detect. Carbon monoxide is formed as
a product of incomplete fuel combustion, and is most commonly found in the
exhaust of internal combustion engines. A divers air supply can be contaminated
by carbon monoxide when the compressor intake is placed too close to the
compressors engine exhaust. The exhaust gases are sucked in with the air and sent
on to the diver, with potentially disastrous results. Carbon monoxide seriously
interferes with the bloods ability to carry the oxygen required for the body to
function normally. The affinity of carbon monoxide for hemoglobin is approxi-
mately 210 times that of oxygen. Carbon monoxide dissociates from hemoglobin
at a much slower rate than oxygen.
Kinetic Theory of Gases. On the surface of the earth the constancy of the atmo-
spheres pressure and composition tend to be accepted without concern. To the
diver, however, the nature of the high pressure or hyperbaric, gaseous environment
assumes great importance. The basic explanation of the behavior of gases under all
variations of temperature and pressure is known as the kinetic theory of gases.
The kinetic theory of gases states: The kinetic energy of any gas at a given tem-
perature is the same as the kinetic energy of any other gas at the same tempera-
ture. Consequently, the measurable pressures of all gases resulting from kinetic
activity are affected by the same factors.