Page 37 - Air Pollution Control Engineering

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Air Quality and Pollution Control 17

Fig. 4. Example of a molecular diffusion sampling manifold.

papers). In addition, ambient air data that could be noted simultaneously include weather
conditions: wind speed and direction, precipitation, temperature, barometric pressure,
relative humidity, and solar radiation (12).

6.2. Source Sampling
Pollutants released from an emission source are measured by proper sampling of the
exhaust gases, which is often complicated by the difficulties and dangers involved. The
sample locations may be hundreds of feet above the ground; the gases may be extreme-
ly hot; residual electrical charges might be present, requiring equipment grounding to
prevent the buildup of dangerous potentials; and the gases could contain poisonous or
toxic substances or active bacteria. Furthermore, the analytical techniques may be