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M400E Ozone Analyzer Operator’s Manual 346BEPA Protocol Calibration
10.1.4. RECOMMENDED STANDARDS FOR ESTABLISHING
TRACEABILITY
Equipment used to produce calibration gasses should be verified against EPA/NIST traceable standards.
Ozone is the only criteria pollutant for which standard concentrations for calibration cannot be directly traceable
to an NIST-SRM (National Institute of Standards - Standard Reference Material).
Such standards are classified into two basic groups: primary standards and transfer standards.
A primary O
3
standard is an O
3
concentration standard that has been dynamically generated and
assayed by UV photometry in accordance with the procedures prescribed by the U.S. Environmental
Protection Agency (EPA) under Title 40 of the Code of Federal Regulations, Part 50, Appendix D
(40 CFR Part 50).
An O
3
transfer standard is a transportable device or apparatus, which, together with associated
operational procedures, is capable of accurately reproducing O
3
concentration standards or producing
accurate assays of O
3
concentrations that are quantitatively related to a primary O
3
standard.
It is worth noting that the requirements for the repeatability and reliability of transfer standards are more stringent
than are those for stationary, primary standards.
A Standard Reference Photometer (SRP) has been developed as a primary O
3
standard by the U.S. National
Institute of Standards and Technology (NIST) and the EPA. It is a highly stable, highly precise, computer-
controlled instrument for assaying O
3
concentrations. NIST maintains one or more “master” SRP’s in lieu of a
Standard Reference Materials (SRM) for ozone. A nationwide network of regionally located SRP’s enables
State and local air monitoring agencies to compare their O
3
standards with authoritative O
3
standards
maintained and operated under closely controlled conditions. Other SRPs are located in foreign countries.
To maintain a uniform and consistent set of references, the US EPA maintains 9 Standard Reference
Photometers (SRP) around the US. It is suggested that the regional office of the EPA be contacted for the
location of a SRP nearby and that the standards be compared. This assures a uniform standard for ozone
concentration is applied everywhere.
Currently, the U.S. SRP Network consists of SRPs located at:
EPA's National Exposure Research Laboratory (NERL), in Research Triangle Park, North Carolina
EPA's Region I Environmental Services Division in Lexington, Massachusetts
EPA's Region II Environmental Services Division in Edison, New Jersey
EPA's Region IV Environmental Services Division in Athens, Georgia
EPA's Region V Environmental Services Division in Chicago, Illinois
EPA's Region VI Environmental Services Division in Houston, Texas
EPA's Region VII Environmental Services Division in Athens, Georgia
EPA's Region VIII Environmental Services Division in Denver, Colorado
The State of California Air Resources Board (CARB) in Sacramento, California
Commercial UV photometers meeting the requirements of a primary ozone standard as set forth in 40 CFR Part
50 are available and are currently being used by air monitoring agencies. Agencies have been encouraged to
compare their primary O
3
standards (and O
3
transfer standards) as part of their routine quality assurance (QA)
programs.
Additionally, to provide a reference against which calibration standards for O
3
must be compared, the U.S. EPA
has prescribed a reference calibration procedure based on the principle of UV light absorption by ozone at a
wavelength of 254 nm
1
. This procedure provides an authoritative standard for all O
3
measurement. Ozone
04315 Rev. C1 173