Transfer Standards For Calibration of Air Monitoring Analyzers for ...

Ozone Transfer Standard Guidance Document 10/2013
ABSTRACT
On February 8, 1979 (Federal Register, 44:8221-8233), the U.S. Environmental Protection Agency
amended Appendix D of Title 40, Code of Federal Regulations (CFR), Part 50, to prescribe a calibration procedure
for the calibration of reference methods for measuring ozone in the atmosphere. The procedure is based on the use
of ultraviolet (UV) photometry as the authoritative standard for ozone and allows the use of transfer standards for
the calibration of ambient ozone monitors, provided such transfer standards are adequately referenced to a UV ozone
standard of higher authority (level) and traceability.
This document is intended as a reference aid to help users select ozone transfer standards and reference
them to a higher level UV standard. It first describes the theory of traceability, defines ozone transfer standards and
then discusses their purpose and role in calibrating ambient ozone analyzers. The various advantages and
disadvantages of ozone transfer standards are pointed out to help users determine whether to use a transfer standard
or the UV procedure directly. Different types of ozone transfer standards are described, including analytical
instruments and ozone generation devices.
The major part of the document is devoted to the procedures necessary to establish the authority of ozone
transfer standards: qualification, verification, and periodic reverification. Qualification consists of demonstrating
that a candidate transfer standard is sufficiently stable (repeatable) to be useful as a transfer standard. Repeatability
is necessary over a range of variables such as temperature, line voltage, barometric pressure, elapsed time, operator
adjustments, or other conditions, any of which may be encountered during use of the transfer standard. Tests and
possible compensation techniques for several such common variables are provided. Detailed verification procedures
are also provided together with the quantitative verification acceptance criteria. Finally, the periodic procedure and
specifications necessary to maintain continuous verification of the transfer standard are given.
For convenience, the UV primary ozone standard procedure from 40 CFR Part 50 is reproduced in
Appendix A. Other appendices give more specific guidance for the qualification and verification of several common
and practical types of transfer standards like ozone generators and ozone analyzers.
This document replaces the 1979 document by the same title (EPA-600/4-79-056). Ultraviolet (UV)
photometry has replaced most of the methods described in the 1979 document. This document removes methods no
longer in use and updates definitions and procedures as needed.
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