In the early 1970s, a better way was needed to monitor stack emissions than by manual stack tests. In general, manual methods are conducted by inserting a probe into a stack, extracting a sample, and analyzing the sample in a laboratory, which is a time‐consuming process. Manual source tests also require a degree of preparation, and the coordination and prior scheduling of a test may result in source operations being highly tuned before such testing takes place. Manual test results, therefore, may not necessarily be representative of day‐to‐day emissions. Clearly, for monitoring plant emissions and the performance of pollution control equipment on a more realistic basis, alternative measurement techniques are needed.


Attempts were made in the 1960s to use ambient air analyzers and process industry analyzers to measure source emissions. Ambient air analyzers were not successful at that time due to the instability of dilution systems. However, process analyzers did prove to be useful, particularly those that employed ultraviolet and infrared photometric techniques. Then, in the late 1960s and early 1970s, successful developments emerged in instrumentation in Germany and the United States. Ambient analyzers were redesigned to measure gases at higher concentration levels, and the so‐called “in‐situ” analyzers were developed, which can measure gases in the stack without sample extraction. These methods, in addition to new German ...

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