Interim EPA Traceability Protocols for the Qualification and Certification of Elemental and Oxidized Mercury Gas Generators
For regulatory purposes, mercury (Hg) calibration gas standards of known concentration and known uncertainty are needed to quality-assure data recorded by Hg continuous emission monitoring systems (CEMS) and measurements made with instrumental Hg reference test methods. Two interim EPA traceability protocols have been prepared that establish procedures for the qualification and certification of elemental and oxidized mercury gas generators. The interim protocols reflect the current state of development for generating and quantifying elemental Hg and mercuric chloride (HgCl2), a form of oxidized mercury.
The interim elemental Hg gas traceability protocol provides procedures to: (1) establish the quantitative output (i.e., “calibration”) of elemental Hg generators; and (2) determine the expanded, combined uncertainty values of the gas standards produced by the elemental Hg generators. The protocol also specifies the maximum allowable uncertainty for the elemental Hg gas standards. A Companion Document has also been prepared that summarizes the methodology used to calculate the certified elemental mercury gas concentrations and associated expanded, combined uncertainty values and includes example calculations of these certified gas concentrations and uncertainty values. Additionally, a series of generic elemental Hg generator spreadsheets have been prepared as templates for calculating these values.
The interim oxidized Hg gas traceability protocol provides procedures for: (1) establishing the NIST traceability and quantitative performance of key components of HgCl2 generators; (2) determining the uncertainty contributed by each of these components; and (3) calculating certified output concentrations and expanded, combined uncertainty values for the gas standards produced by the generators. This protocol also specifies a target uncertainty for the HgCl2 gas standards.
For continuous emission monitoring system (CEMS) applications, these interim protocols apply only to Hg monitoring system span values greater than or equal to 5.0 micrograms per cubic meter (µg/m3).
If you have comments or questions regarding these files, please contact Scott Hedges by e-mail at firstname.lastname@example.org, or by phone at 202-343-9622 or Robin Segall by e-mail at email@example.com, or by phone at 919-541-0893. If possible, please submit your comments by e-mail.
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Companion Document: Treatment of Elemental Mercury Gas Generator Certification Data and Calculation of Uncertainty in support of the Interim EPA Traceability Protocol for Qualification and Certification of Elemental Mercury Gas Generators. (PDF 20pp 215 KB)
Five (5) Generic Spreadsheet Files to calculate the certified elemental mercury gas concentrations and associated uncertainty values. (Note: In addition to using these generic spreadsheets, it is recommended that you contact your specific mercury generator vendor to see if they have vendor-specific spreadsheets you can use.)