Introduction - Mathematics and Statistics for the Environment - page 23

2. 280° must be multiplied by either 5/9 or 9/5. Because the conversion is to the Celsius scale,
we will be moving to a number smaller than 280. Through reason and observation, obvi-
ously, if 280 were multiplied by 9/5, the result would be almost the same as multiplying
by 2, which would double 280 rather than make it smaller. If we multiply by 5/9, the result
will be about the same as multiplying by 1/2, which would cut 280 in half. Because in this
problem we wish to move to a smaller number, we should multiply by 5/9:

(5/9)(280°) = 156.0°C

3. Now subtract 40°.

156.0°C - 40.0°C = 116.0°C

Therefore, 240°F = 116.0°C.

■ EXAMPLE 1.27
Problem: Convert 22°C to Fahrenheit.

Solution:

1. Add 40°:

22° + 40° = 62°

2. Because we are converting from Celsius to Fahrenheit, we are moving from a smaller to a
larger number, and 9/5 should be used in the multiplications:

(9/5)(62°) = 112°

3. Subtract 40:

112° - 40° = 72°

Thus, 22°C = 72°F.
Obviously, knowing how to make these temperature conversion calculations is useful, but it is
generally more practical to use a temperature conversion table.

1.5 CONVERSION FACTORS: AIR POLLUTION MEASUREMENTS
The recommended units for reporting air pollutant emissions are commonly stated in metric system
whole numbers. If possible, the reported units should be the same as those that are actually being
measured. For example, weight should be recorded in grams, and volume of air should be recorded
in cubic meters. When the analytical system is calibrated in one unit, the emissions should be
reported in the same units of the calibration standard. For example, if a gas chromatograph is cali-
brated with a 1-ppm standard of toluene in air, then the emissions monitored by the system should
also be reported in ppm. Finally, if the emission standard is defined in a specific unit, the monitor-
ing system should be selected to monitor in that unit. Tables 1.6 and 1.7 illustrate the conversion
for various volumes to attain 1 part per million (ppm) and also to illustrate conversion for parts per
million in proportion and percent.
The preferred reporting units for the following types of emissions should be

• Nonmethane organic and volatile organic compound emissions ppm, ppb
• Semi-volatile organic compound emissions µg/m 3 , mg/m 3

• Particulate matter (TSP/PM10) emissions µg/m 3

• Metal compound emissions ng/m 3