b. Bodily Effects. Carbon monoxide interferes with the supply of oxygen to the
tissues of the body. Normally, inhaled oxygen is transferred in the lungs to a chemical
known as hemoglobin, which is present in all red blood cells. Hemoglobin then
transports oxygen, by way of the bloodstream, to the tissue cells where transfer takes
place. The affinity of hemoglobin for carbon monoxide is 250 times greater than it is for
oxygen. When carbon monoxide combines with hemoglobin, the transport of oxygen to
the tissue cells is blocked. Without oxygen, cells cannot live, and when the
concentration of carbon monoxide is great enough, death occurs through asphyxiation.
c. Prevention. The most common and most easily recognized potential
exposure to carbon monoxide is in installation motor pool maintenance shops.
Whenever "gasoline powered" (the chemical profile for diesel engine exhaust does not
include much carbon monoxide) vehicle engines are operating, a method of removing
the carbon monoxide-laden exhaust from the vehicle's breathing zone must be used.
This is best accomplished by a combination of natural ventilation and mechanical tail
pipe extension systems that carry the exhaust outside the building. A full discussion of
ventilation systems is found in lesson 4 of this subcourse.
a. Irritant Gases. The gases that have an irritant effect on the mucous
membranes of the respiratory tract and eyes are important occupational hazards.
Gases in this group are chemically very different, but their bodily effects are similar.
Nitrogen dioxide and phosgene will be used as examples of irritant gases.
(1) Sources of exposure. Nitrogen dioxide gas is produced in many
processes, including welding, bleaching, and the manufacturing of explosives.
Phosgene was used as a chemical warfare agent in World War I. It can be accidentally
produced when chemicals called chlorinated hydrocarbons come into contact with a
flame, hot metal, or any other heat source. Trichloroethylene is a chemical commonly
used in vapor-degreasing operations. Contact of this vapor with a heat source can
produce phosgene. Phosgene can also be produced when the vapor of a chlorinated
hydrocarbon comes in contact with ultra-violet radiation such as that produced by
electrical arc welding.
(2) Bodily effects. The body has many mechanisms for protecting its
tissues from injury by harmful gases. For example, some of the irritant gases cause
coughing, sneezing, narrowing of the air passages, or even temporary cessation of
respiration. Also, the tears of the eye and mucus of the respiratory tract tend to dilute
and wash away irritating substances. Irritation of the eyes and upper respiratory tract
may in some cases be severe enough to drive a person out of an area of exposure
before serious damage can occur. On the other hand, some gases damage the lungs,
yet produce only slight irritation of the upper respiratory tract. This effect is
characteristic of phosgene, for example. Other gases may fail to produce warning
symptoms when the amount of gas in the air is increased gradually. The effects of
exposure to a large amount of irritating gases for a short time are different from those