Page 92 - Praxair - Specialty Gases and Equipment Reference Guide

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

1-877-PRAXAIR www.praxairdirect.com C•91