Page 92 - Praxair - Specialty Gases and Equipment Reference Guide
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Grade Specifications






            Praxair Grades
            Environmental Grades                                Standard Grades
            ■  NTRM – NIST Traceable Reference Materials are certified    ■   Primary Standard – Highly accurate mixtures prepared
               by the National Institute of Standards and Technology       gravimetrically on high-precision electronic balances.
               (NIST) and accepted by the Environmental Protection       These standards are analyzed against Praxair Primary
               Agency (EPA), as the highest accuracy standards com-      Laboratory Standards (PPLS) and named to a gravime-
               mercially available. These standards are the regulatory       trically generated concentration.
               equivalent to NIST’s Standard Reference Materials   ■   Certified Standard – These routine calibration mixtures
               (SRMs) and are made up of the same components       are prepared by either gravimetric, volumetric or partial
               and are within the analytical range of NIST SRMs.
                                                                   pressure methods. These standards are analyzed
            ■   EPA Protocols – Used for the calibration and audit       against Praxair Primary Laboratory Standards (PPLS).
               of Continuous Emission Monitors (CEMs), Praxair    ■   Non-Certified – Mixtures are prepared by the same
               EPA Protocols are NIST traceable and produced in       methods and the same care used for Certified Standard
               accordance with the latest EPA specifications found       Grades. Analyses are not reported.
               in document - 600/R97/121 Rev. 9/97.
                                                                ■   Custom – Mixtures prepared to the exact blend
            ■   Primary Master – High accuracy mixtures prepared       tolerance and analytical uncertainty requested.
               gravimetrically on electronic high-precision balances.
               These standards are analyzed and named against NIST
               traceable reference materials.

            ■   Certified Master – These routine calibration mixtures
               are prepared by either gravimetric, volumetric or partial
               pressure methods and analyzed against NIST traceable
               reference materials.
            ■   Dynamic-Blend Master – These zero blend tolerance
               mixtures are prepared on an instrument based dynamic
               blending system. Batches of cylinders from two to
               one hundred can be produced with the identical
               concentrations.

            ■   Dynamic-Blend Standard – These mixtures are
               prepared similarly to the Dynamic  Blend Master.
               Certification of the mixtures is based on process
               accuracy and Praxair Primary Laboratory Standards
               (PPLS).
            All master gases are analyzed and named against
            NIST traceable materials.                                                                               Section C – Mixtures
























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