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One Page Tip #8
Reviewing Span and Range Settings

Once the reports for the fourth quarter and the end of the year are done, it’s time to look forward. Over time, the emission levels at many facilities have declined due to pressure on reducing the plants overall emissions.  Periodic reviews of historically recorded and measured data are a good idea and a smart business practice to keep your monitoring systems in alignment with the emission characteristics of your emissions. The Maximum Potential Concentration (MPC), Maximum Expected Concentration (MEC), and the Maximum Potential Flow (MPF) data sets are used to set the span and range of their respective measurement systems. Finally, these values are part of the Monitoring Plan records and are used as a missing data replacement value under specific missing data periods. For this reason alone, these values and the associated span and range settings need to be kept up to date. 
Minor adjustments typically require the updating of Monitoring Plan records and usually the same blend of gases for calibrations and linearity checks can still be used. But, sometimes a new blend of gas cylinders is required and that triggers successfully passing a full linearity when the cylinders are received. Review the sections listed below carefully. 
In Appendix A, you will find several references to periodically reviewing the span and range settings for the SO2 (§, NOx (§, CO2 (§ and flow (§ systems. At a minimum, an annual evaluation is required. Review these sections of Appendix A carefully to fully understand what additional changes need to be made, such as updating the Monitoring Plan records, triggered by changing the MPCs, the MEC, or span and range settings. 
Carefully review Appendix A, §§ and In cases where a span adjustment is required and the current calibration/linearity gases are unsuitable for use with the new span value, the owner or operator has up to 90 days after the end of the quarter in which the need to adjust the span is identified to implement the change (see Sections and of Appendix A). This allows time to purchase and received new gas cylinders blended to support the new span values. Review P75 Policy Manual Question 9.23 for further guidance.

For questions, suggestions, or for a general chat, please do not hesitate to contact me.

Download the PDF document here.

Jon Konings, Senior Regulatory and Reporting Engineer, ESC

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