(b) Health hazards. The organic solvents, especially the
halogenated varieties, are all hazardous to health in some degree. High
concentration of the vapor may cause the sudden onset of dizziness, headache,
nausea, vomiting, and central nervous system depression leading to
unconsciousness and death; lesser concentrations may also cause serious
illness. Symptoms do not generally appear until after considerable damage
has been done to vital organs such as the liver, kidneys, and bone marrow.
The toxicological properties of hydrocarbons vary. The volatile liquid
hydrocarbons are somewhat narcotic, and the higher molecular-weight members
are irritating. Certain of the aromatic group have carcinogenic
(cancer-producing) properties, and a few of the other high-molecular-weight
compounds are poisonous. Benzene is the most dangerous of the common
hydrocarbons because it has a cumulative effect that can be fatal.
(c) Fire hazard. The presence of hydrocarbons in the
chamber, especially in high O2 atmospheres, presents a serious fire hazard.
(d) Limits. Figure 6-5 shows two limits for total
hydrocarbons in a breathing-gas system as a function of depth. These curves
have been estimated on the basis that the allowable concentration of
hydrocarbons during an extended dive at 1000 feet is 5 percent of that
allowed at atmospheric pressure (see Reference (7)). The slope of the curve
for short-duration dives is the same as that for extended dives.
(5) Oxides of nitrogen are possible trace contaminants of
breathing-gas systems. They are produced by the high-temperature combustion
of oil or gasoline, and they can be contained in air being compressed for a
breathing-gas system. Nitrogen dioxide (NO2) is considerably more toxic
than nitric oxide (NO), acting as an acutely irritating substance. In equal
concentrations, it is more injurious than carbon monoxide. Figure 6-6 shows
two limits of concentration for nitrogen dioxide as a function of depth. The
limit at the surface is from federal specification BB-A-1034. These curves
were based on the assumption that the allowable concentration of nitric oxide
or nitrogen dioxide during an extended dive at a 100-foot depth is 5 percent
of that allowed at atmospheric pressure. The slope of the curve for the
short-duration dive is the same as that of the extended dive.
(6) Sulfur dioxide is probably the most widespread of the man-made
air pollutants, and it is often contained in the air being compressed for a
breathing-gas system. Concentrations in excess of 10 ppm are definitely
irritating. Figure 6-7 shows two limits of sulfur dioxide for breathing-gas
systems as a function of depth. The curves are estimated on the basis that
the allowable concentration of sulfur dioxide during an extended dive at a
1000-foot depth is 5 percent of that allowed at atmospheric pressure. The
slope of the curve for the short-duration dive is the same as that of the
extended dive.
3.
BREATHING GAS CONSUMPTION REQUIREMENTS. In a chamber atmosphere human
breathing gas requirements are based on oxygen that is consumed in
respiration. The diluent gas (nitrogen and/or helium) is not consumed or
altered.
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