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IV. Quality Assurance                  223
























         Fig. 15-4. Ethylene concentrations measured by the DIAL system along a 5-km path
       length near Menlo Park, California. The open circles are ethylene concentrations of samples
       taken at three ground-level locations near the line of sight and analyzed by gas chromatogra-
       phy. Source: Murray, E. A., and Van der Laan, }. E., Appl. Opt. 17, 814-817 (1978).



       stringent regulations requiring well-documented quality assurance pro-
       grams for air quality monitoring activities (13).
         Quality assurance programs are designed to serve two functions:
       (1) assessment of collected air quality data and (2) improvement of the data
       collection process. These two functions form a loop; as air quality data are
       collected, procedures are implemented to determine whether the data are
       of acceptable precision and accuracy. If they are not, increased quality
       control procedures are implemented to improve the data collection process.
         The components of a quality assurance program are designed to serve
       the two functions just mentioned—control and assessment. Quality control
       operations are defined by operational procedures, specifications, calibration
       procedures, and standards and contain the following components:

          1. Description of the methods used for sampling and analysis
          2. Sampling manifold and instrument configuration
          3. Appropriate multipoint calibration procedures
          4. Zero/span checks and record of adjustments
          5. Control specification checks and their frequency
          6. Control limits for zero, span, and other control limits
          7. The corrective actions to be taken when control limits are exceeded
          8. Preventative maintenance
          9. Recording and validation of data
         10. Documentation of quality assurance activities
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