RATA Challenges with Method 30B constraints Page 1 of 2
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§Mercury Concentrations in the stack dropped from 2.4 to 0.9 ug/m3 during the 2-day period of the Unit 2 RATA.
§If the Hg concentration in the flue gas changes during the RATA, one needs to ensure that 30B QA checks, specifically including spike targets and permissible sample mass range, are within tolerance. Even concentration changes that seem insignificant could be very important.
§If the concentration had fallen another 0.2 ug, a new spike target would have to be used, doubling the amount of QA testing required.
Question:
   What does a stack tester tell a customer who wants the difference between the RM and CEM to be less than 0.2 ug?

   Answer:
   Stating that there is any significant difference between  1.0 ug RM and 1.2 ug CEM value implies an accuracy that does not exist.