Page 124 - Fundamentals of Air Pollution

94 6. Sources of Air Pollution

inventory to ± 10% by proper statistical sampling techniques, an emission
factor error of 50% can be overwhelming. It must also be realized that an
uncontrolled source will emit at least 10 times the amount of pollutants
released from one operating properly with air pollution control equipment
installed.
Actual emission data are available from many handbooks, government
publications, and literature searches of appropriate research papers and
journals. It is always wise to verify the data, if possible, as to the validity
of the source and the reasonableness of the final number. Some emission
factors, which have been in use for years, were only rough estimates pro-
posed by someone years ago to establish the order of magnitude of the
particular source.
Emission factors must be also critically examined to determine the tests
from which they were obtained. For example, carbon monoxide from art
automobile will vary with the load, engine speed, displacement, ambient
temperature, coolant temperature, ignition timing, carburetor adjustment,
engine condition, etc. However, in order to evaluate the overall emission
of carbon monoxide to an area, we must settle on an average value that
we can multiply by the number of cars, or kilometers driven per year, to
determine the total carbon monoxide released to the area.

C. Data Gathering
To compile the emission inventory requires a determination of the num-
ber and types of units of interest in the study area. It would be of interest,
for example, to know the number of automobiles in the area and the
number of kilometers each was driven per year. This figure would require
considerable time and expense to obtain. Instead, it can be closely approxi-
mated by determining the liters of gasoline sold in the area during the
year. Since a tax is collected on all gasoline sold for highway use, these
figures can be obtained from the tax collection office.
Data regarding emissions are available from many sources. Sometimes
the same item may be checked by asking two or more agencies for the
same information. An example of this would be to check the liters of
gasoline sold in a county by asking both the tax office and the gasoline
dealers association. Sources of information for an emission inventory in-
clude (1) city, county, and state planning commissions; (2) city, county,
and state chambers of commerce; (3) city, county, and state industrial
development commissions; (4) census bureaus; (5) national associations
such as coal associations; (6) local associations such as the County Coal
Dealers Association; (7) individual dealers or distributors of oil, gasoline,
coal, etc.; (8) local utility companies; (9) local fire and building departments;
(10) data gathered by air pollution control agencies through surveys, sam-
pling, etc.; (11) traffic maps; and (12) insurance maps.