United States
Environmental Protection
Agency
Performance of the Proposed
New Federal Reference
Method for Measuring Ozone
Concentrations in Ambient Air
Technical Report
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EPA/600/R-14/432 | October, 2014 | www.epa.gov/ord
United States
Environmental Protection
Agency
Performance of the Proposed
New Federal Reference
Method for Measuring Ozone
Concentrations in Ambient Air
Technical Report
Office of Research and Development
National Exposure Research Laboratory
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Russell Long, Eric S. Hall, Melinda Beaver, Rachelle M. Duvall, and Surender Kaushik
National Exposure Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, NC, USA 27709
Keith Kronmiller, Michael Wheeler, Samuel Garvey, Zora Drake
Alion Science and Technology
Research Triangle Park, NC, USA 27709
Frank McElroy, Consultant
The McConnell Group
Rockville, MD, USA 20850
Process Modeling Research Branch
Human Exposure and Atmospheric Sciences Division
National Exposure Research Laboratory
U.S. EPA Office of Research and Development
October 2014
Disclaimer/Notice
The information in this document has been funded wholly by the U.S. Environmental Protection Agency. It has been
subjected to the Agency's peer and administrative review and has been approved for publication as an EPA document.
Mention of products or trade names does not indicate endorsement or recommendation for use by the Agency.
Acknowledgments
The U.S. Environmental Protection Agency (EPA) wishes to thank the following collaborating institutions and their
staff members for their contribution to the success of this research. The National Aeronautics and Space Administration
Langley Research Center, the National Oceanic and Atmospheric Administration, the Maryland Department of the
Environment, the Texas Commission on Environmental Quality, the Colorado Department of Public Health and the
Environment, and Alion Science and Technology are acknowledged for their contributions in supporting EPA in
the execution of complex laboratory and ambient data collections and analyses. Jim Szykman, Jonathan Krug, Lew
Weinstock, Joann Rice, Tim Buckley, Roy Fortmann, Lindsay Stanek, Tim Watkins, Jennifer Orme-Zavaleta, and
Dan Costa (EPA) are acknowledged for their efforts to ensure the success of the research effort reported here. EPA
would also like to thank the members of the Clean Air Scientific Advisory Committee's (CAS AC) Air Monitoring and
Methods Subcommittee (AMMS) and Ed Hanlon (Designated Federal Officer for CAS AC/AMMS, EPA) for their
substantial effort in reviewing EPA's proposed adoption of the new nitric oxide-chemiluminescence Federal Reference
Method for ozone in ambient air.
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Executive Summary
The current Federal Reference Method (FRM) for measuring
concentrations of ozone in ambient air, described in EPA
regulations at 40 CFR Part 50, Appendix D, is based on
the dry, gas-phase, chemiluminescence reaction between
ethylene and any ozone that may be present in air samples.
This methodology is technically sound and has well served
its role in ozone monitoring and as an FRM for many years
since its establishment in 1971. However, the method
now no longer meets the full needs of an FRM because no
manufacturer of ozone-monitoring instruments currently
offers an FRM analyzer for sale. Existing FRM analyzers
are largely obsolete and poorly supported (if supported at
all) by their manufacturers, and, consequently, all current
ozone monitoring is carried out with other types of monitors
(equivalent methods). A new FRM for ozone is needed to
meet the needs that the existing FRM can no longer fulfill.
A rather similar measurement method, based on the dry.
gas-phase, chemiluminescence reaction between nitric oxide
(NO) and any ozone present in ambient samples has been
subjected to extensive laboratory and field testing (along with
an FRM and other Federal Equivalent Methods [FEMs]) to
determine its performance and other attributes relative to
those of the existing FRM. This report describes the nature
and results of this testing and documents the conclusion
that this alternative nitric oxide-chemiluminescence
(NO-CL) method has performance as good as or better
than the existing FRM. Further, at least two NO-CL ozone-
monitoring analyzers are commercially available (from
one manufacturer) and have been designated by the U.S.
Environmental Protection Agency as FEMs for use in ozone-
monitoring networks. Therefore, this alternative method is
shown to be well suited as a supplemental FRM for ozone
to serve in the FRM role as a practical reference standard
for candidate FEMs and for quality assurance of ozone-
monitoring data.
MI
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IV
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Table of Contents
List of Tables vi
List of Figures vii
Acronyms/Abbreviations ix
1.0 Introduction 1
2.0 Issues of Concern Regarding the Ozone FRM 3
3.0 Ozone Monitor/Analyzer Types 5
3.1 Ethylene-Chemiluminescence Ozone Analyzers (FRM) 5
3.1.1. Theory of Operation 5
3.1.2. Advantages 5
3.1.3. Disadvantages 5
3.1.4. Interferences 5
3.1.5. Current Status 5
3.2 NO-CL Ozone Analyzers (FEM) 6
3.2.1. Theory of Operation 6
3.2.2. Advantages 6
3.2.3. Disadvantages 6
3.2.4 Interferences 6
3.2.5. Current Status 6
3.3. UV Photometric Ozone Analyzers (FEM) 6
3.3.1. Theory of Operation 6
3.3.2. Advantages 7
3.3.3. Disadvantages 7
3.3.4. Interferences 7
3.3.5. Current Status 7
3.4 Other Ozone Measurement Methodologies 7
3.4.1 Open-Path Ozone Monitors 7
3.4.2 Sensors 7
4.0 Performance Tests of the NO-CL Method 9
4.1 Test Analyzer 9
4.2 Manufacturer Tests 9
4.3EPATests 10
4.3.1 Background 10
4.3.2 Approach 10
4.3.2.1 Laboratory Tests 10
4.3.2.2 Ambient Evaluations 11
4.3.2.3 Quality Assurance 12
4.3.3 Results 12
4.3.3.1 Laboratory Test Results 12
4.3.3.2 Ambient Evaluation Results 13
5.0 Conclusions 17
6.0 References. . . 19
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List of Tables
Table 1. Comparison of Model T265 andMode!211 Ozone Analyzer's Manufacturer's Performance Specifications with the
Existing and Proposed Performance Requirements for Ozone FRM and FEM Analyzers 9
Table 2. FRMs and FEMs for Ozone Used in the Evaluation Study 10
Table 3. Ozone Analyzer Inventory Deployed During Each Field Study^sed for calibration and nightly zero and
span checks 11
Table 4. Comparison of EPA Laboratory Test Results to Existing and Proposed Revised FRM and FEM Performance
Requirements 12
Table 5. Comparison of 1-h EPA Ozone Analyzer Results Collected During the Various Field Deployments 13
Table 6. Comparison of Maximum Daily 8-h-Average Ozone Analyzer Results Collected During the Various Field
Deployments 16
VI
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List of Figures
Figure 1. Apparatus for performing laboratory-based evaluations of FRM/FEM analyzers 11
Figure 2. Comparison of the 1-h-average Bendix 8002 (FRM) and T265 (NO-CL) ozone results in ambient air at Houston, TX.
during September 2013 (left) and at Denver, CO, during July and August 2014 (right) 13
Figure 3. Comparison of the 1-h-average Model 211 (SL-UV) and T265 (NO-CL) ozone results in ambient air at Houston
(LaPorte), TX, during September 2013 (top) and at Denver, CO, during July and August 2014 (bottom) 14
Figure 4. Comparison of the 1-h-average EC9810 and T265 (NO-CL) ozone results in ambient air at Padonia, MD, during July
2011 (top) and comparison of the 1-h-average Model 205 and T265 (NO-CL) ozone results in ambient air at RTF, NC.
during June and July 2012 (bottom). Both the EC9810 and the Model 205 employ the UV photometric method and
contain sample conditioning systems to remove water from the sample stream 14
Figure 5. Comparison of the 1-h-average 49i and T265 (NO-CL) ozone results in ambient air at RTF, NC, during June and July
2012 (top) and at Houston (LaPorte), TX, during September 2013 (bottom). The 49i employs the UV photometric
method but does not contain a sample conditioning system to remove water from the sample stream 15
Figure 6. Comparison of the maximum daily 8-h-average (MDA8) ozone results in ambient air at Houston (LaPorte), TX.
during September 2013 (top) and at Denver, CO, during July and August 2014 (bottom) 15
VII
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Acronyms/Abbreviations
AIRS
API
AQS
C2H4
CFR
Cal/Dil
C12
CO
C02
DC
DISCOVER-AQ
DOAS
EPA
FEM
FR
FRM
H20
H2S
Hg
hv
IE
Ambient Air Innovative Research Site
Advanced Pollution Instrumentation
Air Quality System
ethylene
Code of Federal Regulations
calibration/dillution
chlorine
carbon monoxide
carbon dioxide
direct current
Deriving Information on Surface
Conditions from Column and Vertically
Resolved Observations Relevant to Air
Quality
differential optical absorption
spectroscopy
U.S. Environmental Protection Agency
Federal Equivalent Method
Federal Register
Federal Reference Method
water
hydrogen sulfide
mercury
photon
interference equivalent
MDA8
MFC
NAAQS
NIST
NO
NO2
NO-CL
02
03
OD
Pb
PM
PMT
R2
RH
RMS
RTF
SLAMS
SL-UV
S02
T
URL
UV
V
voc
x
y
ZAG
maximum daily 8-h average
mass flow controller
National Ambient Air Quality Standards
National Institute of Standards and
Technology
nitric oxide
nitrogen dioxide
nitric oxide-chemiluminescence
oxygen
ozone
outer diameter
lead
paniculate matter
photomultiplier tube
coefficient of determination
relative humidity
root mean square
Research Triangle Park, NC
State and Local Air Monitoring Station
scrubberless ultraviolet
sulfur dioxide
temperature
upper range limit
ultraviolet
volts
volatile organic compound
linear regression independent variable
linear regression dependent variable
zero air generator
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1.0
Introduction
Under the Clean Air Act, the U.S. Environmental Protection
Agency (EPA) has established National Ambient Air Quality
Standards (NAAQS) (i.e., concentration limits) for six air
pollutants, known as the criteria air pollutants: (1) carbon
monoxide (CO), (2) lead (Pb), (3) nitrogen dioxide (NO2),
(4) sulfur dioxide (SO2), (5) ozone (O3), and (6) paniculate
matter (PM). These NAAQS are set forth in Title 40, Part
50 of the Code of Federal Regulations (40 CFR Part 50).
EPA and the States are jointly responsible for monitoring the
ambient air for these six criteria pollutants. This monitoring
is carried out as part of a national network of approximately
4000 monitoring sites, called the State and Local Air
Monitoring Stations (SLAMS). The air quality data obtained
from these sites are collected in EPA's Air Quality System
(AQS) database, along with other information, and are used
for
• determining compliance with the NAAQS.
• assessing effectiveness of State Implementation Plans
in addressing NAAQS nonattainment areas.
• characterizing local, State, and national air quality
status and trends, and
• associating health and environmental damage with air
quality levels and concentrations.
To assure the accuracy, integrity, and uniformity of the
SLAMS air quality monitoring data collected, EPA has
established one or more Federal Reference Methods
(FRMs) for measuring each criteria pollutant. These FRMs
are set forth in several appendixes to 40 CFR Part 50 and
typically specify a particular measurement technique to
be implemented in a commercially produced monitoring
instrument. These monitoring instruments must be shown to
meet specific performance and other requirements detailed
in the EPA regulations at 40 CFR Part 53, in which case the
instrument may be designated by EPA as an FRM analyzer.
Also, to encourage innovation and development of new air
quality monitoring methods, EPA has provided for Federal
Equivalent Methods (FEMs). An FEM is not constrained
to the particular measurement technique specified in the
corresponding FRM. However, an FEM must meet the same
or similar performance requirements as specified for the
corresponding FRM, and in addition, it must show a high
degree of comparative agreement with collocated FRM
measurements at one or more field testing sites. These FEM
requirements also are detailed in 40 CFR Part 53, and a
monitor that is shown to meet all applicable requirements
may be designated by EPA as an FEM monitor.
Section 2.1 of Appendix C to 40 CFR Part 58 mandates the
use of either FRMs or FEMs for SLAMS monitoring to
determine compliance with the NAAQS. In addition, FRMs
are used in assessing the quality of the SLAMS monitoring
data and as reference standards of comparison for designation
of FEM monitors. The current listing of all designated FRMs
and FEMs can be found at http://www.epa.gov/ttnamtil/files/
ambient/criteria/reference-eauivalent-methods-list.pdf.
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2.0
Issues of Concern Regarding the Ozone FRM
The current FRM for measuring concentrations of ozone
in ambient air, described in EPA regulations at 40 CFR
Part 50, Appendix D,1'2 is based on the dry, gas-phase.
chemiluminescence reaction between ethylene (C2H4) and
any ozone that may be present in air samples. This method
was established in 1971, and, at that time and for many
years after, it was widely used for monitoring ozone, as
implemented in a variety of ozone analyzers manufactured by
several instrument manufacturers. These analyzers proved to
provide accurate and reliable monitoring data in the SLAMS
for many years. This FRM is specific for ozone and has no
significant interferences. It served its role well as an FRM
and remains a technically sound method today.
Unfortunately, the method requires a constant supply of
ethylene for continuous operation. Ethylene is a gas that
is stored in high-pressure gas cylinders and is flammable
and explosive. A large gas cylinder is required for extended
operation, and the use of such gas cylinders often is restricted
to an outdoor location or entirely precluded at some potential
monitoring sites, rendering use of the FRM analyzers
inconvenient, if not problematic, at least at many potential
monitoring sites. Ozone analyzers utilizing an ultraviolet
(UV) photometric measurement technique, which became
available in the 1980s, do not require a supply of gas or any
other reagent and are much more convenient to install and
operate. Several UV photometric analyzer models have been
designated by EPA as FEMs, and such monitors (along with
a few other types of FEMs) have completely replaced the use
of FRM analyzers in SLAMS monitoring. With no demand
for FRM analyzers for SLAMS monitoring, instrument
manufacturers have stopped producing them. The last ozone
FRM analyzer was designated by EPA in 1979.
Although FEMs can fill the need for routing monitoring.
FRM analyzers are required for other important purposes.
such as quality assurance of monitoring data and for
reference measurements for the required FEM comparability
qualification. With no manufacturer of ozone-monitoring
instruments currently offering an FRM analyzer for sale,
the existing FRM can no longer fulfill the needs of an FRM.
Previously manufactured FRM analyzers are largely obsolete.
poorly supported (if supported at all) by their manufacturers.
and likely now to be well beyond their expected operational
lifetime. Because of the lack of availability and poor support.
they are entirely inadequate for FRM-specific applications.
For these reasons, a new FRM is needed.
A similar measurement technique based on the dry, gas-phase
chemiluminescence reaction of nitric oxide (NO) with
ozone in sampled air has been identified as a potential
and advantageous candidate for a new ozone FRM. This
report documents the extensive laboratory and field testing
and analyses that have been carried out to examine the
viability of this nitric oxide-chemiluminescence (NO-CL)
method as a proposed new FRM for ozone. In addition, this
report documents laboratory and field testing and analysis
of additional methodologies that were also evaluated as
potential FRMs. The results of this examination support the
conclusion that the NO-CL method has the performance
characteristics and other attributes necessary and appropriate
for a new FRM for ozone.
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3.0
Ozone Monitor/Analyzer Types
Various types of methods have been developed to monitor
ozone concentrations in ambient air, and analyzers using
several different methodologies have been designated by EPA
as either FRM or FEM monitors. The current ozone FRM is
the ethylene-chemiluminescence method, based on the dry.
gas-phase reaction between ethylene and ozone as described
in 40 CFR Part 50, Appendix D.
Because of the significant limitations of the current ethylene-
chemiluminescence type FRM analyzers, other types of
ozone-measurement technologies have been examined as
possible candidates for a new ozone FRM. The types of
ozone methods that have achieved FRM or FEM status are
described briefly below, with consideration of the FEMs as
possible candidates for a new FRM.
3.1 Ethylene-Chemiluminescence Ozone
Analyzers (FRM)
3.1.1. Theory of Operation
These analyzers implement the measurement principle
specified for FRM analyzers, described in Appendix D of 40
CFR Part 50. Ethylene-chemiluminescence ozone analyzers
measure ozone concentrations by using the dry, gas-phase
chemiluminescence reaction of ethylene with ozone in a
flowing air sample. The overall reaction mechanism for
ethylene-chemiluminescence generally proceeds as follows:
C2H4 + O3 -> CO2 + H2CO* + CHO- + *OH.
The reaction generates electronically activated formaldehyde
that luminesces (which is indicated by an asterisk) in the high
UV to visible portion of the spectrum (380 nm to 550 nm)
and vibrationally activated hydroxide ions that luminesce
in the visible light to low infrared portion of the spectrum
(550 nm to 800 nm). The number of photons emitted during
the reaction is directly proportional to the amount of ozone
present. When air without ozone (zero air) or an air sample
containing ozone is introduced into the analyzer mixing
chamber/reaction cell, the emitted photons (if any) are
counted by a photomultiplier tube (PMT), with its response
centered at 440 nm, then the count is converted to ozone
concentration by a software-driven algorithm.3 Measurements
are referenced to certified ozone concentration standards
according to the calibration procedure specified as part of the
FRM.
3.1.2. Advantages
The method is largely free of measurement interferences. It
has been implemented successfully by several instrument
manufacturers in various ozone analyzer models, which (in
years past) have proved to provide stable and reliable ozone
measurements in monitoring network operation. This method
is not impacted by the known interferents (hydrogen sulfide
[H2S], carbon dioxide [CO2], NO, water [H2O], meta-xylene,
volatile organic compounds [VOCs], mercury [Hg], NO2,
SO2, and chlorine [C12]), which are found in ambient air and
can reduce the operational performance and reliability of the
UV-based ozone analyzers. The resulting chemiluminescence
from the reaction between ethylene and ozone is specific to
ozone (i.e., there are no other atmospheric substances that
react with ethylene resulting in chemiluminescence at or near
the 440-nm wavelength). The reaction between ethylene and
ozone is a nameless one.
3.1.3. Disadvantages
The method requires a constant supply of ethylene, which
is a dangerous, flammable, and potentially explosive gas
typically stored in high-pressure gas cylinders. The use of
such gas cylinders may be inconvenient and is often restricted
by building fire codes or other monitoring site limitations.
Following the development and availability of other types of
ozone monitors (such as those utilizing the UV absorption
method) that do not require a supply of reagent gas, use of
such alternative methods in ozone-monitoring networks
completely supplanted the use of FRM analyzers in virtually
all current ozone-monitoring networks. With little or no
demand for FRM analyzers, manufacturers no longer produce
them. There are no ethylene-chemiluminescence FRM
analyzers currently used in EPA's SLAMS network.
3.1.4. Interferences
The chemiluminescence from the reaction between ethylene
and ozone is specific to ozone, thus the method is not
impacted significantly by typical concentrations of potential
interferents (such as H2S, CO2, NO, meta-xylene, VOCs.
Hg, NO2, SO2, and C12) that may occur in ambient air.
There are no other atmospheric substances that react with
ethylene resulting in chemiluminescence near 440 nm. Some
sensitivity to variations in water vapor concentration (because
of quenching of the chemiluminescence reaction) generally
does not present a significant measurement problem.
3.1.5. Current Status
There are no ethylene-chemiluminescence analyzers currently
in EPA's SLAMS network.
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3.2 NO-CL Ozone Analyzers (FEM)
3.2.1. Theory of Operation
This method is quite similar to that of the ethylene-
chemiluminescence FRM. NO-CL ozone analyzers measure
ozone concentrations by using the fact that the dry, gas-phase
reaction between nitric oxide and ozone generates nitrogen
dioxide in an activated state (NO2*), and oxygen (O2).4>5 As
each unstable NO2* returns to a lower energy state (NO2), it
emits a photon (hv). The reaction causes luminescence in a
broadband spectrum ranging from visible light to infrared
light (approximately 590 nm to 2800 nm). The two-step
gas-phase reaction proceeds as follows:
NO + O
3 NO2* + O2,
then
NO2* -> NO2 + hv.
The number of photons emitted during the reaction is directly
proportional to the amount of ozone present, and the photons
are counted by a PMT. The photon count is converted to
ozone concentration by a software-driven algorithm.
3.2.2. Advantages
Similar to the FRM, the NO-CL method has no significant
interferents. The method behaves in the same manner as
the ethylene-chemiluminescence FRM when exposed to the
same interferents listed in 40 CFR Part 53, Table B-3 (e.g..
H2S, CO2, and H2O) that are found in ambient air, which
may have an effect on the response of the widely-used
UV-spectrophotometric ozone methods in certain situations.
The NO-CL method is designated as an FEM. It meets all
of the same performance specifications (as specified in
40 CFR Part 53) as the existing FRM and is comparable
to the existing FRM from a measurement perspective. In
addition, the NO-CL devices currently are in manufacturing
production. The method has been implemented successfully
by at least one instrument manufacturer, which offers two
models that have been designated by EPA as FEMs.
In addition, extensive laboratory and field testing by EPA
has shown that the NO-CL method exhibits performance that
equals or exceeds that of FRM analyzers and is, thus, a fully
qualified candidate for consideration as a proposed new FRM
for ozone.
3.2.3. Disadvantages
The method requires a constant supply of nitric oxide
gas (approximately 1% [w/w]), which is stored in a high-
pressure gas cylinder. Because nitric oxide is not flammable
or explosive, monitoring site restrictions on the use of a
high-pressure nitric oxide gas cylinder may be less than
those for ethylene gas needed for FRM analyzers, but
analyzer installation is still somewhat inconvenient. For
use in nonmonitoring FRM applications, where shorter
term operation is likely, the use of small, more convenient.
compressed-gas cylinders (as opposed to the large cylinders
required for long-term operation) is possible. High
concentrations of nitric oxide such as those found in the nitric
oxide cylinders are toxic (asphyxiant).
3.2.4 Interferences
The NO-CL method is not impacted significantly by typical
concentrations of potential interferents (such as H2S, CO2,
H2O, NO, meta-xylene, VOCs, Hg, NO2, SO2, and C12)
that may occur in ambient air. Further testing by EPA has
confirmed the lack of any significant interferences from
compounds that might be encountered in ambient air
monitoring.
3.2.5. Current Status
Currently, one commercial manufacturer has had an NO-CL
instrument type (with two different model numbers)
designated in 2011 as an FEM.
3.3. UV Photometric Ozone Analyzers (FEM)
3.3.1. Theory of Operation
UV photometric ozone analyzers determine ozone
concentrations by quantitatively measuring the attenuation
of light due to absorption by ozone present in an absorption
cell at the specific wavelength of 254 nm.6'7 The ozone
concentration generally is determined through a two-step
process in which the light intensity passing through the
sample air (I) is compared with the light intensity passing
through similar sample air from which all ozone is first
removed (I0). The ratio of these two light-intensity values
(I/I0) provides the measure of the light absorbed at 254 nm.
and the ozone concentration in the sample then is determined
through the use of the Beer-Lambert Law as:
I/I0 = e-KLC(C=l/KLln[I/I0]),
where L is the length of the absorption cell (in centimeters).
C is the ozone concentration (in parts per million), and
K is the absorption cross section of ozone at 254 nm at
standard atmospheric temperature and pressure conditions
(308 atnr1 cm'1). Some systems have one absorption cell with
I and I0 measured alternately, whereas other systems have two
separate absorption cells with I and I0 measured concurrently.
Photometric monitors for ozone generally use mercury lamps
as the UV light source, with optical filters to attenuate lamp
output at other than the 254 nm wavelength. Zero air for the
reference measurement typically is obtained with manganese
dioxide, heated silver wool, or nitric oxide gas to "scrub"
ozone from the sample air while preserving other substances
in the sample air that absorb at 254 nm, so that their effects
are cancelled in the differential I/L measurement.
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3.3.2. Advantages
UV photometric ozone analyzers require no external gas
supply or other reagents and are compact, easy to install.
and convenient to operate. Various analyzer models from
several instrument manufacturers have been shown to meet
FEM performance requirements and have been designated
as FEMs by EPA. These UV FEM analyzers currently
represent the vast majority of analyzers used in State and
local ozone monitoring networks. In general, UV photometric
measurements compare very well with those obtained from
FRM analyzers. UV ozone analyzers represent more recent
measurement technology than the current FRM and would be
advantageous for consideration as a new FRM because they
currently are in manufacturing production, and their use is
widespread.
3.3.3. Disadvantages
The integrity of the ozone zero air scrubber is critical and
may enable measurement interferences if it does not perform
adequately (see section 3.3.4 Interferences). Similarly, any
tendency of the scrubber to fail to effectively remove all
ozone from the reference sample will result in a measurement
bias. The integrity of the scrubber has been shown to be
affected to some extent by changes in sample air humidity.
These shortcomings make the method an unlikely candidate
for consideration as a new FRM for ozone. The UV
photometric method is impacted by known interferences
(see section 3.3.4 Interferences) that often are found in
ambient air and may reduce the operational performance and
reliability of this method.
3.3.4. Interferences
Various substances that may be present at some monitoring
sites (including H2S, CO2, H2O, meta-xylene, Hg, and
aromatic hydrocarbon compounds) have strong absorbance of
light at 254 nm and may cause measurement interferences if
the zero air ozone scrubber fails to pass any such substances
unattenuated in the zero reference air.
3.3.5. Current Status
UV photometric analyzers are the most widely used methods
for ozone compliance measurements. There were 1,367 UV
photometric analyzers in EPA's SLAMS network as of June
2014. A newly introduced and recently designated (June
18, 2014, 79 FR 34734) ozone FEM analyzer represents
a variation of the UV photometric method, known as the
"scrubberless" UV photometric method,4 that specifies
removal of ozone from the sample air for the zero reference
by a gas-phase reaction with nitric oxide rather than via
a conventional solid chemical scrubber. The nitric oxide
reacts with the ozone much faster than with other potential
interfering compounds and is very effective at removing the
ozone without affecting other compounds that may be present
in the ambient air sample. The differential UV measurement
then effectively can eliminate interferences to an insignificant
level. EPA currently is evaluating this variation of the UV
photometric method for future consideration as an ozone
FRM.
3.4 Other Ozone Measurement Methodologies
3.4.1 Open-Path Ozone Monitors
EPA has designated two open-path air analyzers as FEMs.
These analyzers operate on the principle of differential
optical absorption spectroscopy (DOAS) over an open path
of several meters up to 1 kilometer.7 The DOAS system
analyzes the spectral absorption fingerprint of several
ambient air pollutants over a range of visible or near-
UV wavelengths. This technology was not evaluated as a
potential candidate FRM for ozone because its open-path
nature makes it difficult to assess in a laboratory setting.
3.4.2 Sensors
Sensors are small, relatively inexpensive monitoring devices
that represent a new class of air pollution measurement
devices. These gas-measurement sensors, such as those
used to measure ozone, are based on electrochemical, metal
oxide, and spectroscopic technologies. Some sensors have
undergone preliminary testing in EPA's Office of Research
and Development laboratory in Research Triangle Park
(RTF), NC.8 A number of sensors have been evaluated in
the field in Houston (September 2013), and in Denver, CO
(July and August 2014). EPA continues its laboratory and
field analysis of ozone sensors. Preliminary results will be
documented in future technical reports and peer-reviewed
scientific journal articles.
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4.0
Performance Tests of the NO-CL Method
4.1 Test Analyzer
The NO-CL method—the proposed new FRM—is
implemented in two ozone analyzers manufactured by
Teledyne Advanced Pollution Instrumentation (API), Inc.
(9480 Carroll Park Drive, San Diego, CA 92121-5201,
858-657-9800, www.teledyne-api.comX Both Models 265E
and T265 provide user-selectable ozone measurement ranges
of 0 to 100 ppb to 0 to 2000 ppb (0 to 2 ppm) and identical
performance, with the following manufacturer ratings.
Zero noise
Span noise
Lower detectable
limit
Zero drift
Span drift
<0.15 ppb (root mean square [RMS])
<0.5% of reading (RMS) above 100 ppb
<0.3 ppb
<0.5 ppb/24 h
<0.5% of full scale/24 h
Rise and fall time <20 s to 95% of final reading
Linearity < 1% of full scale
Precision <0.5% of reading
Sample flow rate 500 cmVmin ±10%
The Model T265 features a more advanced user interface
than the standard Model 265E.
4.2 Manufacturer Tests
Both analyzer models were designated by EPA as FEMs
(identified as Equivalent Method No. EQOA-0611-199)
on October 7, 2011 (76 FR 62402). This designation
indicates that a representative Model 265 analyzer was
tested in accordance with the FEM test and performance
requirements specified in 40 CFR Part 53 and has, to EPA's
satisfaction, been shown to meet all such requirements.
In laboratory FEM tests, the candidate FEM analyzer is
required to show performance equal to or better than the
FRM/FEM requirements given in Table B-l of Part 53.
These requirements are listed in Table 1, along with revised
performance requirements that EPA intends to propose for
new ozone FRM and FEM analyzers.
Table 1 compares the manufacturer's claimed performance
for the analyzer (taken from the manufacturer's published
specification sheet) with both the existing FRM and FEM
performance requirements, as well as the revised and new
requirements that EPA intends to propose for new FRM
and FEM analyzers. The manufacturer's performance
specifications for some of performance parameters defined
Table 1. Comparison of Model T265 and Model 211 Ozone Analyzer's Manufacturer's Performance Specifications with
the Existing and Proposed Performance Requirements for Ozone FRM and FEM Analyzers
Proposed New FRM and FEM Performance Limit
Specifications3
Model 211
Model T265 Manufacturer's Manufacturer's
Claimed Performance Claimed Performance
Performance Parameter Specification1 Specification1
1. Range
2. Noise
3. Lower detectable limit
4. Interference equivalent
Each interferent
Total, all interferents
5. Zero drift, 12-and24-h
6. Span drift, 80% of URL
7. Lag time
8. Rise time
9. Fall time
10. Precision
20% URL
80% URL
0-0.5 ppm (0-0.1 to 0-2.0
available)
<0.00015ppm
<0.0003 ppm
Not specified
Not specified
<0.0005 ppm
<0.5%(of0.5ppmURL)
<10s
<20s
<20s
<0.5% of reading (0.001 ppm)
<0.5% of reading (0.004 ppm)
0.0005-2.0 ppm
0.001 ppm
±0.002 ppm
<0.007 ppm
<0.001 ppm
<0.8%
1 min
1 min
1 min
<0.4% of reading
<1% of reading
FRM and FEM
Performance Limit
Specifications2
0-0.5 ppm
0.005 ppm
0.010 ppm
±0.02 ppm
0.06 ppm
±0.02 ppm
±5.0%
20 min
15 min
15 min
0.010 ppm
0.010 ppm
Standard Range Lower Range
0-0.5 ppm
0.001 ppm
0.003 ppm
±0.005 ppm
2%4
2%4
0-<0.5 ppm
0.0005 ppm
0.001 ppm
±0.005 ppm
±0.004 ppm
±3.0%
2 min
2 min
2 min
±0.002 ppm
±3.0%
2 min
2 min
2 min
2%4
2%4
1The manufacturer may not specify performance for all of the performance parameters defined by the FRM/FEM requirements or may measure
them differently. The manufacturers' specification sheets for Model T265 and Model 211 can be found in references 12 and 13, respectively.
2Current performance specifications taken from Table B-1 to Subpart B of Part 53—Performance Limit Specifications for Automated Methods
3ln conjunction with the proposal of a new FRM for O3, EPA intends to propose revised, more stringent performance specifications, along with
new performance specifications applicable to optional lower ranges for O3 analyzers.
4Standard deviation expressed as percent of the URL.
-------
for FRM and FEM analyzers are not given or may be
described somewhat differently. As noted above, the
designation of the analyzer as an FEM confirms that actual
FEM tests of these performance parameters, as carried out
by the manufacturer, were examined by EPA, and those test
results were found to show that that the analyzer met all
existing FEM requirements. (These manufacturer-conducted
FEM test results are included in a confidential business
information claim covering the entire FEM application and.
therefore, cannot be presented here.) Table 1 also suggests a
high probability that the analyzer would meet the proposed
revised and new requirements, as well.
The FEM test requirements also include a field test to
compare ozone measurements from the candidate method
with concurrent measurements from an FRM analyzer
at a suitable field test site (40 CFR Part 53, Subpart C).9
Agreement must be shown within 20 to 40 ppb, depending on
the concentration level. Again, designation of the Model 265
as an FEM by EPA indicates that such a test was performed
by the manufacturer, and that the results were examined by
EPA and were determined to meet the FEM test requirements
for comparability. (Again, these test results cannot be
presented here because they are included in the confidential
business information claim for the FEM application.)
4.3 EPA Tests
4.3.1 Background
EPA conducted extensive laboratory and ambient testing of
the NO-CL method (Model T265 analyzer) (1) to verify that
the method meets all existing requirements for FRM and
FEM analyzers and its capability to serve the functions of
a reference method and (2) to determine its ability to meet
proposed revised and new requirements for FRM and FEM
analyzers. The tests also evaluated the analyzer's general
performance relative to the FRM (Bendix Model 8002
Ozone Analyzer; Reference Method No. RFOA-0176-007)
and several other FEM ozone analyzers, namely Thermo
Scientific Model 49i Photometric Ambient Ozone Analyzer
(Equivalent Method No. EQOA-0880-047), Ecotech EC9810
Ozone Analyzer (Equivalent Method No. EQOA-0193-
091) and 2B Technologies Model 205 (Equivalent Method
No. EQOA-1410-190) and Model 211 (Equivalent Method
No. EQOA-0514-215). The Bendix Model 8002 is a true
ethylene-chemiluminescence FRM analyzer that has been
refurbished to full operational status. These analyzers.
operation principle, and designation information are
summarized in Table 2.
4.3.2 Approach
4.3.2.1 Laboratory Tests
The laboratory-based tests were conducted in accordance
with the test procedures detailed in Subpart B of 40 CFR
Part 53.10 Prior to laboratory-based testing, all analyzers
under evaluation were calibrated according to manufacturers'
operation manuals and in accordance with FRM requirements
listed in 40 CFR 50, Appendix D. During laboratory testing.
all analyzers were connected to a common sampling manifold
(Ace Glassware) via 6.4-mm (0.25-in) outer diameter (OD).
perfluoroalkoxy Teflon sampling lines. Paniculate filters
(5-um pore size) were fitted to each analyzer's inlet port.
Air containing known concentrations of the test atmosphere
(ozone) and/or interferent gas was provided to the manifold
inlet as needed to conduct the test procedures. An exhaust
line was attached to the manifold outlet and placed into the
laboratory's 6-in ceiling vent to allow a continuous flow-
through-design feature. All calibration gas concentrations and
laboratory test atmospheres were established using a National
Institute of Standards and Technology (NIST)-traceable and
programmable dynamic dilution calibration system (Teledyne
API Model T700U). Constituents were delivered to the
system from either the T700U enclosed ozone generator
(with NIST-traceable photometer) or EPA protocol (±2%
accuracy) reference gas standards. Dilution air that had been
scrubbed of all contaminants was delivered to the mixing
system to meet test gas dilution needs. Relative humidity
(RH) within the system was produced and controlled through
the use of a deionized water bubbler. Temperature and RH
were measured with a temperature/RH probe consisting of a
precision thin-film platinum, 1000-Q. resistive temperature
device that employs a linear resistance change with
temperature converted to a 0- to 10-V DC output proportional
to 0 to 100.0 °C. The sensor was calibrated using a NIST-
traceable reference thermometer. The RH sensor consists
of a HyCal, Inc., IH-3602-C monolithic integrated circuit
capacitance sensor that produces a linear voltage proportional
to RH (0- to 10-V DC output directly proportional to 0 to
100% RH). The RH sensor was calibrated using saturated
Table 2. FRMs and FEMs for Ozone Used in the Evaluation Study
Manufacturer and Model
Bendix Model 8002 (FRM)
Teledyne API Model T265 (FEM)
2B Technologies Model 211 (FEM)
2B Technologies Model 205 (FEM)
Ecotech EC9810 (FEM)
Thermo Scientific Model 49i (FEM)
Teledyne API Model T700U1
Teledyne API Model 7011
Operation Principle
Ethylene-chemiluminescence
NO-CL
"Scrubberless" UV photometric (dual beam)
UV photometric (dual beam)
UV photometric
UV photometric
Dynamic dilution calibrator
Zero air generator
FRM/FEM Designation
Federal Register: Vol. 41, page 5145, 02/04/76
Federal Register: Vol. 76, page 62402,10/07/11
Federal Register: Vol.79, pages 34734-34735, 06/18/2014
Federal Register: Vol.75, pages 22126-22127, 04/27/10
Federal Register: Vol. 58, page 6964, 02/03/93
Federal Register: Vol. 45, page 57168, 08/27/1980
1Used for calibration and nightly zero and span checks
10
-------
Excess
Glass Sampling
Manifold
API T700 Cal/Dil System
API M701 ZAG
,t
lyian
MFC
, n
c<
3-way Teflon
Solenoid
RH/Temp
Meter
Solenoid switched by API T700 Control Output bit
Figure 1. Apparatus for performing laboratory-based evaluations of FRM/FEM analyzers.
salt solutions that have known RH over headspace. The
temperature and RH signal response were shown on a liquid
crystal display and logged using an in-laboratory data-
acquisition system (Envidas Ultimate). A schematic diagram
of the apparatus used during the laboratory-based evaluations
is given in Figure 1.
4.3.2.2 Ambient Evaluations
Ambient evaluations of the proposed FRM and the various
FEM methods were conducted during field-intensive
studies at the Ambient Air Innovative Research Site (AIRS)
located on the EPA campus in RTF during the springs and
summers of 2012 and 2014. Ambient evaluations also were
performed as part of the National Aeronautics and Space
Administration's Deriving Information on Surface Conditions
from Column and Vertically Resolved Observations
Relevant to Air Quality (DISCOVER-AQ) project conducted
during July 2011 near Baltimore, MD; September 2013 in
Houston (La Porte); and July and August 2014 near Denver.
During field-intensive studies, instruments were calibrated
according to manufacturers' operation manuals and in
accordance with FRM requirements listed in 40 CFR 50.
Appendix D. During the ambient evaluation campaigns.
nightly automated zero and span checks were performed
to monitor the validity of the calibration and to control for
drifts or variations in the span or zero response. Both the
calibration gas concentrations and the nightly zero and span
gas concentrations were delivered using the T700TJ dynamic
dilution calibration system described in section 4.3.2.1. The
analyzers were contained within a temperature-controlled
shelter during the sampling campaigns. A glass inlet with
sampling height located approximately 5 m above ground
Table 3. Ozone Analyzer Inventory Deployed During Each Field Study
Field Deployment
(Date)
Baltimore MD (July
2011)
AIRS 2012 (June
and July 2012)
Houston (LaPorte),
TX (September
2013)
Ozone Analyzer
Teledyne API Model T265 (FEM)
EcotechEC9810(FEM)
Teledyne API Model T700U1
Teledyne API Model 7011
Teledyne API Model T265 (FEM)
2B Technologies Model 205 (FEM)
Bendix Model 8002 (FRM)
Thermo Scientific Model 49i (FEM)
Teledyne API Model T700U1
Teledyne API Model 7011
Teledyne API Model T265 (FEM)
2B Technologies Model 211 (FEM)
Bendix Model 8002 (FRM)
Thermo Scientific Model 49i (FEM)
Teledyne API Model T700U1
Teledyne API Model 7011
Field Deployment
(Date)
AIRS 2014 (April-
June 2014)
Ozone Analyzer
Teledyne API Model T265 (FEM)
2B Technologies Model 211 (FEM)
2B Technologies Model 205 (FEM)
Bendix Model 8002 (FRM)
Teledyne API Model T700U1
Teledyne API Model 7011
Teledyne API Model T265 (FEM)
Denver, CO (July 2B Technologies Model 211 (FEM)—2 analyzers collocated
and August 2014) Bendix Mode| 80Q2 (FRM)
Teledyne API Model T700U1
Teledyne API Model 7011
'Used for calibration and nightly zero and span checks
11
-------
level and a subsequent sampling manifold were shared by
all instruments. Table 3 summarizes the different ozone
analyzers evaluated during each field deployment.
4.3.2.3 Quality Assurance
As previously stated, the laboratory-based tests were
conducted in accordance with the test procedures detailed in
Subpart B of 40 CFR Part 53.10. Prior to both laboratory-
based and ambient testing, all analyzers under evaluation
were calibrated according to manufacturers' operation
manuals (per FEM designations) and in accordance with
FRM requirements listed in 40 CFR 50, Appendix D. In
addition, all research detailed in this report was conducted
under the EPA approved QAPP-AB-12-02 - Quality
Assurance Project Plan: Ambient Air Monitoring Methods
Assessment and Development for Criteria Gas National
Ambient Air Quality Standards.
4.3.3 Results
4.3.3.1 Laboratory Test Results
The average laboratory test results are summarized in Table
4, which is presented in a format similar to that given in
Table B-l of Subpart B (Part 53). The result of each test
trial is compared with the prescribed test limit requirement
to determine whether the test result passes or fails. All test
results must pass the test criteria to pass the test requirement
for that performance parameter. Clearly, the test results
reported in Table 4 show that the Model T265 met all existing
and revised proposed performance requirements proposed
for new ozone FRM and FEM analyzers for the standard
measurement range (0 to 0.5 ppm). Even the test results for
total interferents met the existing requirements for these
parameters. (This requirement is proposed to be withdrawn in
the revised performance requirements and is shown in Table
1 but not in Table 4.)
The laboratory-based tests were carried out with the test
analyzer operating with a 0- to 0.5-ppm measurement
range, so the test results are not directly comparable with
the proposed new, lower range performance requirements
for noise, lower detectible limit, span drift, and precision.
However, the results given in Table 4 clearly show that
the T265 analyzer would meet the proposed lower range
performance requirements as well.
In addition, the EPA-performed laboratory test results
reported in Table 4 show that other methods, including the
Model 211 and Model 49i, met all existing and revised
performance requirements proposed for new ozone FRM and
FEM analyzers for the standard measurement range (0 to 0.5
ppm). Similar to those for the T265 analyzer, the laboratory-
based tests for the other methods were carried out in the
0- to 0.5-ppm analyzer measurement range. The results also
clearly suggest that the Model 211 and Model 49i analyzer
Table 4. Comparison of EPA Laboratory Test Results to Existing and Proposed Revised FRM and FEM Performance
Requirements
Performance
Parameter
1. Range
2. Noise
3. Lower detectable
limit
4. Interference
equivalent
-Each
interferent
5. Zero drift, 12- and
24-h
6. Span drift, 80%
of URL
7. Lag time
8. Rise time
9. Fall time
10. Precision
20% URL
80% URL
Teledyne-API Model 2B Technologies
T265 Model 211
0-0.1 ppm
0-1.0 ppm
<0.0005 ppm
<0.0006 ppm
<0.0001 ppm
<0.0001 ppm
<0.5%
<1 min
<1 min
<1 min
<0.4%
<0.6%
0-2.0 ppm
<0.0005 ppm
<0.001 ppm
<0.0002 ppm
<0.0001 ppm
<0.5%
<1 min
<1 min
<1 min
<0.5%
<0.5%
Thermo Model 49i
0-0.5 ppm
0-1 .0 ppm
<0.0005 ppm
<0.001 ppm
<0.0001 ppm
0.01 ppm for water
vapor
<0.0002 ppm
<0.5%
<1 min
<2 min
<2 min
<0.4%
<0.4%
FRM and FEM Proposed New FRM and FEM Performance
Performance Limit Limit Specifications'
Specifications1 Standard Range Lower Range
0-0.5 ppm
0.005 ppm
0.010 ppm
±0.02 ppm
±0.02 ppm
±5.0%
20 min
15 min
15 min
0.010 ppm
0.010 ppm
0-0. 5 ppm
0.001 ppm
0.003 ppm
±0.005 ppm
±0.004 ppm
±3.0%
2 min
2 min
2 min
2%3
2%3
0-<0.5 ppm
0.0005 ppm
0.001 ppm
±0.005ppm
±0.002 ppm
±3.0%
2 min
2 min
2 min
2%3
2%3
1 Current performance specifications taken from Table B-1 to Subpart B of Part 53—Performance Limit Specifications for Automated Methods
2 In conjunction with the proposal of a new FRM for O3, EPA intends to propose revised, more stringent performance specifications, along with
new performance specifications applicable to optional lower ranges for O3 analyzers.
3 Standard deviation expressed as percent of the URL.
12
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T265 vs Bendix 8002
LaPorte, TX September 4-28, 2013
T26S Ozone, ppb
T265 vs Bendix 8002
Denver, CO July 13-August 12, 2014
y = 1.025X 10.474
R1 = 0.993
Figure 2. Comparison of the 1-h-average Bendix 8002 (FRM) and T265 (NO-CL) ozone results in ambient air at
Houston, TX, during September 2013 (left) and at Denver, CO, during July and August 2014 (right).
likely would meet the proposed lower range performance
requirements, with the exception of the water interference
result for the Model 49i (see Table 4).
4.3.3.2 Ambient Evaluation Results
Table 5 gives comparisons (linear regressions) of 1-h EPA
test results for the NO-CL ozone analyzer (Teledyne API
Model T265) collected during the various field deployments.
In ambient air evaluations in Houston and Denver, hourly
average ozone results from the T265 compared very closely
with those from the Bendix 8002 FRM, as shown in Figure 2.
Linear regression results for comparison of the T265 with the
Bendix 8002 FRM in Houston and Denver give slopes within
2.5% of unity and sub-parts-per-billion intercepts (Table
5, Figure 2). It should be noted that the Bendix 8002 FRM
operated by EPA during the ambient evaluations was quite
an old instrument, possibly not performing completely up to
original factory specifications. This is evident in comparing
the linear regression results of the T265 with the various
other analyzers during each of the campaigns (Table 5).
Generally, more scatter (lower R2 value) and deviations from
a slope of 1.0 are observed when comparing the T265 with
the Bendix 8002 (Table 5, Figure 2) than when comparing
the T265 with other analyzer types (Table 5, Figures 3 and
4). The exception to this is comparison of the 1-h T265
results with those obtained from the 49i during both the RTF
summer 2012 and Houston summer 2013 studies, as shown in
Figure 5. The 49i analyzer is a conventional UV photometric
method that does not employ a sample conditioning system to
Table 5. Comparison of 1-h EPA Ozone Analyzer Results Collected During the Various Field Deployments
Comparison x vs. y
Baltimore, MD: July 2011
T265vs. EC9810
AIRS, NC: June and July 2012
T265 vs. Bendix 8002
AIRS, NC: June and July 2012
T265 vs. Model 205
AIRS, NC: June and July 2012
T265vs. 49i
Houston (LaPorte), TX: September 2013
T265 vs. Bendix 8002
Houston (LaPorte), TX: September 2013
T265 vs. Model 211
Houston (LaPorte), TX: September 2013
T265 vs. Model 205
Houston (LaPorte), TX: September 2013
T265vs. 49i
AIRS, NC: April-June 201 4
T265 vs. Bendix 8002
AIRS, NC: April-June 201 4
T265 vs. Model 211
AIRS, NC: April-June 201 4
T265 vs. Model 205
Denver, CO: July and August 201 4
T265 vs. Bendix 8002
Denver, CO: July and August 201 4
T265vs. Model 21 1#1
Denver, CO: July and August 201 4
T265vs. Model 21 1#2
n
689
756
756
735
564
564
564
564
924
938
729
670
670
665
x Average (ppb)
42.3
35.3
35.3
35.3
30.3
30.3
30.3
30.3
35.3
35.3
36.1
45.7
45.7
45.7
y Average (ppb)
42.4
37.8
35.6
35.4
31.1
32.4
32.6
32.9
36.6
36.4
35.5
47.3
45.9
45.6
Linear Regression
y=1.002x-0.046
y=1.013x-0.817
y=1.006x+0.123
y=1.019x+0.121
y=1.016x+0.346
y=0.998x+2.192
y=0.999x+2.574
y=0.974x+3.444
y=1.027x+0.085
y=0.996x+1.090
y=0.973x-0.180
y=1.025x+0.424
y=0.989x+0.652
y=0.995x+0.075
R2 Comments
0.997
„ „„, Scatter in data attributed to
Bendix 8002
0.998
0.998
0.998
0.999
0.999
0.997
0.996
0.999
0.999
0.993
0.999
0.999
13
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100
90
T26Svs Model 211
La Porte, TX September 4-28,2013
y = 0.998X + 2.19Z
R' = 0.999
TZ65 Ozone, ppb
T26SVS Model 211
Denver, CO July IB-August 12,2014
= 0995x« 0.076
R' = 0.999
T26S Ozone, ppb
Figure 3. Comparison of the 1-h-average Model 211
(SL-UV) and T265 (NO-CL) ozone results in ambient
air at Houston (LaPorte), TX, during September 2013
(top) and at Denver, CO, during July and August 2014
(bottom).
T265 vs EC 9810
Padonia, MD July 1-31, 2011
60
T265 ozone, ppb
T265 vs Model 205
RTP, NC June 22-July 31, 2012
y - 1.006* t 0.123
R1 = 0.998
T265 Ozone, ppb
Figure 4. Comparison of the 1-h-average EC9810 and
T265 (NO-CL) ozone results in ambient air at Baltimore
(Padonia), MD, during July 2011 (top) and comparison
of the 1-h-average Model 205 and T265 (NO-CL) ozone
results in ambient air at RTP, NC, during June and July
2012 (bottom). Both the EC9810 and the Model 205
employ the UV photometric method and contain sample
conditioning systems to remove water from the sample
stream.
remove water (a known interferent in UV photometric ozone
determination, see section 3.3.4) from the sample stream.
During the RTP and Houston studies, RH values were high
(>85%), possibly resulting in a measurement interference
associated with the 49i. The closest agreement was obtained
while comparing the T265 results with the Model 211 results
during multiple field studies (Table 5, Figure 3). Linear
regression results for comparison of the T265 with the Model
211 in Houston, RTP (2014), and Denver give slopes within
1% of unity (Table 5, Figure 3). A slightly elevated offset (~2
ppb) was observed during the Houston study. Further analysis
of the T265 and Model 211 and Bendix 8002 datasets
indicates the offset is associated with the Model 211.
The current NAAQS for ozone is 0.075 ppm (75.0 ppb) in
the form of the annual fourth-highest daily maximum 8-h
concentration, averaged over 3 years. To enable evaluation of
the T265 and other FRM and FEM analyzers' performance
with respect to monitoring for the ozone NAAQS, maximum
daily 8-h-average (MDA8) ozone concentrations were
calculated.11 Table 6 gives a comparison (linear regression)
of MDA8 ozone analyzer results collected during the various
field deployments. In ambient air evaluations in Houston and
14
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T265 vs 49i
RTF, NC June 22-July 31, 2012
40 50
T265 Ozone, ppb
T26S vs 49i
LaPorte, TX September 4-28, 2013
T265 Ozone, ppb
Figure 5. Comparison of the 1-h-average 49i and T265
(NO-CL) ozone results in ambient air at RTF, NC, during
June and July 2012 (top) and at Houston (LaPorte), TX,
during September 2013 (bottom). The 49i employs the
UV photometric method but does not contain a sample
conditioning system to remove water from the sample
stream.
Maximum Daily 8 hr Average Ozone
LaPorte, TX September 4-28,2013
i Bendix 8002 • Model 211 Linear (Bendix 8002) Linear (Model 211)
10
0
10 20 30 40 50 60 70 80 90 100
T265MDA8 Ozone, ppb
Maximum Daily 8 hr Average Ozone
Denver, CO July 13-August 12,2014
• Bendix 8002 • Model 211 Linear (Bendix 8002) Linear (Model 211)
¥ = 0.979* - 0.775
R' = 0.986
I so
30
20
¥ = 0.978x + 1.329
R! = 0.997
40 50 60
T265MDA8 Ozone, ppb
Figure 6. Comparison of the maximum daily 8-h-average
(MDA8) ozone results in ambient air at Houston
(LaPorte), TX, during September 2013 (top) and at
Denver, CO, during July and August 2014 (bottom).
Denver, MDA8 ozone results from the T265 compared very
closely with those from the Bendix 8002 FRM and Model
211, as shown in Figure 6.
Clearly and as expected, ambient air measurement
performance of the Model T265 is comparable with that of
other FRM and FEM analyzers. Operation of the analyzer
was very similar to that of the FRM analyzer, and it was
straightforward to install, operate, and calibrate, particularly
with the advanced user interface of the Model T265. No
problems or user difficulties were encountered, and all
operational observations indicated that the analyzer could
serve well as an FRM analyzer if the proposed NO-CL ozone
FRM were to be adopted. According to the manufacturer.
Models T265 and 265E have the same specified performance.
Therefore, the results of Model T265 testing should apply
equally to the Model 265E, notwithstanding some differences
in the user interface between the two models.
15
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Table 6. Comparison of Maximum Daily 8-h-Average Ozone Analyzer Results Collected During the Various Field
Deployments
Comparison x vs. y
Baltimore, MD: July 2011
T265vs. EC9810
AIRS, NC: June and July 2012
T265 vs. Bendix 8002
AIRS, NC: June and July 2012
T265 vs. Model 205
AIRS, NC: June and July 2012
T265 vs. 49i
Houston (LaPorte), TX: September 2013
T265 vs. Bendix 8002
Houston (LaPorte), TX: September 2013
T265 vs. Model 211
Houston (LaPorte), TX: September 2013
T265 vs. Model 205
Houston (LaPorte), TX: September 2013
T265 vs. 49i
AIRS, NC: April-June 201 4
T265 vs. Bendix 8002
AIRS, NC: April-June 201 4
T265 vs. Model 211
Denver CO: July and August 201 4
T265 vs. Bendix 8002
Denver, CO: July and August 201 4
TQRRwo Unrlol 9-l-lii-l
n
28
30
30
30
24
24
24
24
46
46
29
29
x Average (ppb)
62.9
52.1
52.1
52.1
42.9
42.9
42.9
42.9
50.5
50.5
58.2
58.2
Average (ppb)
63.1
53.4
52.6
53.4
43.4
44.8
44.8
45.3
52.1
51.4
60.2
58.2
Linear Regression
y=0.993x+0.657
y=1. 059-1 .766
y=1.009x-0.001
y=0.992x+1.695
y=0.998x+0.824
y=0.996x+2.296
y=1.004x+2.149
y=0.963x+4.131
y=0.973x+2.927
y=0.977x+2.086
y=0.979x-0.775
y=0.978x+1.329
R2
0.984
0.974
0.997
0.983
0.998
0.999
0.999
0.998
0.976
0.996
0.986
0.997
Comments
Scatter in data attributed to
Bendix 8002
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5.0
Conclusions
Tests of the NO-CL method using the Teledyne API Model
T265 analyzer show it to meet all existing performance
requirements for candidate ozone FRM and FEM analyzers.
It has previously been shown to meet all FEM performance
requirements and is listed by EPA as a designated equivalent
method (EQOA-0611-199). The tests also show it would meet
proposed revised requirements for ozone FRM and FEM
analyzers as well. The analyzer is commercially available and
is shown to be operationally fully acceptable as an alternative
FRM analyzer if the proposed new ozone FRM is adopted as
a modification to 40 CFR Part 50, Appendix D. Therefore.
the NO-CL method, as represented by the Teledyne API T265
analyzer, is shown to be well suited as an FRM for ozone
to serve in the FRM role as a practical reference standard
for candidate FEMs and for quality assurance of ozone
monitoring data.
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6.0
References
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