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WHAT YOU SHOULD KNOW ABOUT
AIR
POLL'
U TION CONTROL SYSTEMS
AND THE SERVICE THEY REQUIRE
Source of Emissions
During the combustion process in an
automotive
engine,
some
of the fuel
(hydrocarbons)
fails to bum
completely and is discharged into the engine crank-
case or exhaust system. Additional hydrocarbons are
emitted into the atmosphere through evaporation of
gasoline vapors from the fuel tank and carburetor.
Of the total hydrocarbons coming from uncontrolled
automobiles, about 20% are emitted from the crank-
case, 20% from the fuel
system
and 60% from the
engine exhaust.
In addition to hydrocarbons, carbon monoxide
and oxides of nitrogen are also formed during the
combustion process. These are also discharged
into
the exhaust system.
What General Motors Has Done
Since research on the control of vehicle emissions
46
first began some 20 years ago, General Motors has
developed a number of control systems which are
highly effective in reducing undesirable emissions.
(These systems are discussed in some detail, in the
following pages of this section). The progress made
is evidenced by a reduction in hydrocarbon emissions
of 80% since 1960. Control of hydrocarbon emis-
sions is important since, when subjected to sunlight
under the proper conditions, they react with other
gases to form photochemical smog, which
is
so prev-
alent in Los Angeles.
In addition, carbon monoxide emissions have been
reduced by about 65 percent compared with 1960
model cars without controls. Although carbon mon-
oxide does not enter into complex photochemical
smog reaction, it is toxic at high concentrations and
j
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