Dive_Man_ChangeA

2-16 Change A U.S. Navy Diving Manual—Volume 1 2-10.5 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. 2-10.6 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 diving research. 2-10.7 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. 2-10.8 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 diver’s air supply can be contaminated by carbon monoxide when the compressor intake is placed too close to the compressor’s 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 blood’s 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. 2-10.9 Kinetic Theory of Gases. On the surface of the earth the constancy of the atmo- sphere’s 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.