September 2000
Environmental Technology
Verification Report
COSA Instruments Model
7000 Vario Plus
Portable Emission Analyzer
Prepared by
Batfelle
. . . Putting Technology To Worh
Battel le
Under a cooperative agreement with
oEPA U.S. Environmental Protection Agency
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September 2000
Environmental Technology Verification
Report
ETV Advanced Monitoring Systems Center
COSA Instruments Model 7000 Vario Plus
Portable Emission Analyzer
By
Thomas Kelly
Ying-Liang Chou
Charles Lawrie
James J. Reuther
Karen Riggs
Battelle
Columbus, Ohio 43201
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Notice
The U.S. Environmental Protection Agency (EPA), through its Office of Research and Develop-
ment has financially supported and collaborated in the extramural program described here. This
document has been peer reviewed by the Agency and recommended for public release. Mention
of trade names or commercial products does not constitute endorsement or recommendation by
the EPA for use.
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Foreword
The U.S. Environmental Protection Agency (EPA) is charged by Congress with protecting the
Nation's air, water, and land resources. Under a mandate of national environmental laws, the
Agency strives to formulate and implement actions leading to a compatible balance between
human activities and the ability of natural systems to support and nurture life. To meet this
mandate, the EPA's Office of Research and Development (ORD) provides data and science
support that can be used to solve environmental problems and to build the scientific knowledge
base needed to manage our ecological resources wisely, to understand how pollutants affect our
health, and to prevent or reduce environmental risks.
The Environmental Technology Verification (ETV) Program has been established by the EPA, to
verify the performance characteristics of innovative environmental technology across all media
and to report this objective information to permitters, buyers, and users of the technology, thus
substantially accelerating the entrance of new environmental technologies into the marketplace.
Verification Organizations oversee and report verification activities based on testing and Quality
Assurance protocols developed with input from major stakeholders and customer groups
associated with the technology area. At present, there are twelve environmental technology areas
covered by ETV. Information about each of the environmental technology areas covered by ETV
can be found on the Internet at http://www.epa.gov/etv.htm.
Effective verifications of monitoring technologies are needed to assess environmental quality,
and to supply cost and performance data to select the most appropriate technology for that
assessment. In 1997, through a competitive cooperative agreement, Battelle was awarded EPA
funding and support to plan, coordinate, and conduct such verification tests, for "Advanced
Monitoring Systems for Air, Water, and Soil" and report the results to the community at large.
Information concerning this specific environmental technology area can be found on the Internet
at http://www.epa.gov/etv/07/07_main.htm.
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Acknowledgments
The authors wish to acknowledge the support of all those who helped plan and conduct the
verification test, analyze the data, and prepare this report. In particular we recognize Brian
Canterbury, Paul Webb, Darrell Joseph, and Jan Satola of Battelle, and Tiberius Wolf and Chris
Hales of COSA Instruments.
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Contents
Notice ii
Foreword iii
Acknowledgments iv
List of Abbreviations x
1. Background 1
2. Technology Description 2
3. Test Design and Procedures 3
3.1 Introduction 3
3.2 Laboratory Tests 4
3.2.1 Linearity 6
3.2.2 Detection Limit 7
3.2.3 Response Time 7
3.2.4 Interrupted Sampling 7
3.2.5 Interferences 7
3.2.6 Pressure Sensitivity 8
3.2.7 Ambient Temperature 9
3.3 Combustion Source Tests 9
3.3.1 Combustion Sources 9
3.3.2 Test Procedures 11
4. Quality Assurance/Quality Control 15
4.1 Data Review and Validation 15
4.2 Deviations from the Test/QA Plan 15
4.3 Calibration of Laboratory Equipment 17
4.4 Standard Certifications 17
4.5 Performance System Audits 18
4.5.1 Technical Systems Audit 18
4.5.2 Performance Evaluation Audit 18
4.5.3 Audit of Data Quality 20
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5. Statistical Methods 21
5.1 Laboratory Tests 21
5.1.1 Linearity 21
5.1.2 Detection Limit 22
5.1.3 Response Time 23
5.1.4 Interrupted Sampling 23
5.1.5 Interferences 23
5.1.6 Pressure Sensitivity 24
5.1.7 Ambient Temperature 24
5.2 Combustion Source Tests 25
5.2.1 Accuracy 25
5.2.2 Zero/Span Drift 25
5.2.3 Measurement Stability 25
5.2.4 Inter-Unit Repeatability 26
5.2.5 Data Completeness 26
6. Test Results 27
6.1 Laboratory Tests 27
6.1.1 Linearity 27
6.1.2 Detection Limit 29
6.1.3 Response Time 30
6.1.4 Interrupted Sampling 30
6.1.5 Interferences 30
6.1.6 Pressure Sensitivity 33
6.1.7 Ambient Temperature 35
6.1.8 Zero/Span Drift 37
6.2 Combustion Source Tests 38
6.2.1 Relative Accuracy 38
6.2.2 Zero/Span Drift 41
6.2.3 Measurement Stability 43
6.2.4 Inter-Unit Repeatability 46
6.3 Other Factors 47
6.3.1 Cost 47
6.3.2 Data Completeness 47
6.3.3 Maintenance/Operational Factors 47
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7. Performance Summary 48
8. References 49
Figures
2-1. COSA Instruments 7000 Vario Plus 2
3-1. Manifold Test Setup 6
Tables
3-1. Identity and Schedule of Tests Conducted on COSA Instruments
7000 Vario Plus Analyzers 3
3-2. Summary of Interference Tests Performed 8
3-3. Span Concentrations Provided Before and After Each Combustion Source 13
4-1. Results of QC Procedures for Reference Analyzers for Testing
COSA Instruments 7000 Vario Plus Analyzers 16
4-2. Equipment Type and Calibration Date 17
4-3. Performance Evaluation Results on NO/NOz Standards 19
4-4. Performance Evaluation Results on 02 and Temperature Measuring Equipment 20
6-la. Data from NO Linearity Test of COSA Instruments 7000 Vario Plus Analyzers 27
6-lb. Data from N02 Linearity Test of COSA Instruments 7000 Vario Plus Analyzers 28
6-2. Statistical Results for Test of Linearity 28
6-3. Estimated Detection Limits for COSA Instruments 7000 Vario Plus Analyzers 29
6-4. Response Time Data for COSA Instruments 7000 Vario Plus Analyzers 31
6-5. Response Time Results for COSA Instruments 7000 Vario Plus Analyzers 32
6-6. Data from Interrupted Sampling Test with COSA Instruments
7000 Vario Plus Analyzers 32
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6-7. Pre- to Post-Test Differences as a Result of Interruption of Operation of
COSA Instruments 7000 Vario Plus Analyzers 32
6-8. Data from Interference Tests on COSA Instruments 7000 Vario Plus Analyzers 33
6-9. Results of Interference Tests of COSA Instruments 7000 Vario Plus Analyzers 33
6-10. Data from Pressure Sensitivity Test for COSA Instruments
7000 Vario Plus Analyzers 34
6-11. Pressure Sensitivity Results for COSA Instruments 7000 Vario Plus Analyzers 35
6-12. Data from Ambient Temperature Test of COSA Instruments
7000 Vario Plus Analyzers 36
6-13. Ambient Temperature Effects on COSA Instruments 7000 Vario Plus Analyzers 37
6-14. Data from Linearity and Ambient Temperature Tests Used to Assess
Zero and Span Drift of the COSA Instruments 7000 Vario Plus Analyzers 37
6-15. Zero and Span Drift Results for the COSA Instruments
7000 Vario Plus Analyzers 38
6-16a. Data from Gas Rangetop in Verification Testing of COSA Instruments
7000 Vario Plus Analyzers 39
6-16b. Data from Gas Water Heater in Verification Testing of
COSA Instruments 7000 Vario Plus Analyzers 39
6-16c. Data from Diesel Generator at High RPM in Verification Testing of
COSA Instruments 7000 Vario Plus Analyzers 40
6-16d. Data from Diesel Generator at Idle in Verification Testing of
COSA Instruments 7000 Vario Plus Analyzers 40
6-17. Relative Accuracy of COSA Instruments 7000 Vario Plus Analyzers 41
6-18. Data Used to Assess Zero and Span Drift for COSA Instruments
7000 Vario Plus Analyzers on Combustion Sources 42
6-19. Results of Zero and Span Drift Evaluation for COSA Instruments
7000 Vario Plus Analyzers 43
6-20. Data from Extended Sampling Test with Diesel Generator at Idle,
Using COSA Instruments 7000 Vario Plus Analyzers 44
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6-21. Results of Evaluation of Measurement Stability for COSA Instruments
7000 Vario Plus Analyzer 46
6-22. Summary of Repeatability 47
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List of Abbreviations
AMS
Advanced Monitoring Systems
ANSI
American National Standards Institute
Btu/hr
British thermal unit per hour
ccm
cubic centimeter per minute
CEM
continuous emission monitor
CO
carbon monoxide
co2
carbon dioxide
DC
direct current
EPA
U.S. Environmental Protection Agency
ETV
Environmental Technology Verification
FID
flame ionization detector
gpm
gallons per minute
kW
kilowatt
LOD
limit of detection
1pm
liters per minute
m3
cubic meters
nh3
anhydrous ammonia
NIST
National Institute of Standards and Technology
NO
nitric oxide
NOx
nitrogen oxides
no2
nitrogen dioxide
o2
oxygen
PE
performance evaluation
ppm
parts per million, volume
ppmC
parts per million carbon
QA
quality assurance
QC
quality control
QMP
Quality Management Plan
RPM
revolutions per minute
SAS
Statistical Analysis System
so2
sulfur dioxide
UHP
ultra-high purity
X
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Chapter 1
Background
The U.S. Environmental Protection Agency (EPA) has created the Environmental Technology
Verification Program (ETV) to facilitate the deployment of innovative environmental tech-
nologies through performance verification and dissemination of information. The goal of the
ETV Program is to further environmental protection by substantially accelerating the acceptance
and use of improved and cost-effective technologies. ETV seeks to achieve this goal by pro-
viding high quality, peer reviewed data on technology performance to those involved in the
design, distribution, permitting, purchase and use of environmental technologies.
ETV works in partnership with recognized testing organizations, stakeholder groups consisting
of regulators, buyers and vendor organizations, and with the full participation of individual
technology developers. The program evaluates the performance of innovative technologies by
developing test plans that are responsive to the needs of stakeholders, conducting field or
laboratory tests (as appropriate), collecting and analyzing data, and preparing peer reviewed
reports. All evaluations are conducted in accordance with rigorous quality assurance protocols to
ensure that data of known and adequate quality are generated and that the results are defensible.
The EPA's National Exposure Research Laboratory and its verification organization partner,
Battelle, operate the Advanced Monitoring Systems (AMS) Center under ETV. The AMS Center
has recently evaluated the performance of portable nitrogen oxides monitors used to determine
emissions from combustion sources. This verification statement provides a summary of the test
results for the COSA Instruments Model 7000 Vario Plus Portable Emission Analyzer.
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Chapter 2
Technology Description
The objective of the ETV A VIS Center is to verify the performance characteristics of environ-
mental monitoring technologies for air, water, and soil. This verification report provides results
for the verification testing of COSA Instruments 7000 Vario Plus analyzers. The following
description of the 7000 Vario Plus analyzer is based on information provided by the vendor.
The COSA 7000 Vario Plus is specifically designed to measure 02, CO, NO, N02, and S02
emissions from a variety of combustion sources, including boilers, incinerators, and internal
combustion engines. The COSA 7000 Vario Plus uses electrochemical sensors, with a high range
CO sensor and a hydrocarbon sensor also available for applications involving internal com-
bustion engine emission testing. The unit also measures gas and ambient temperatures and stack
draft. Calculated parameters include carbon dioxide, combustion efficiency, excess air, and flue
gas losses. A customized hard copy of the measurements can be printed out, or up to 300 com-
plete combustion tests can be stored to be downloaded to a PC.
The COSA 7000 Vario Plus also includes a complete sample conditioning system with a heated
sample gas hose, sample gas cooler, and condensate removal system. The Vario Plus dimensions
are 22" x 13" x 8.5" and it weighs 30 pounds. Options include flow measurement; soot measure-
ment; automatic remote, unattended measurement with data
logging; 4 to 20mA DC outputs; and
T ~'mrl remote handheld interface, printer, or
¦ keyboard.
The two COSA 7000 Vario Plus
analyzers subjected to the ETV testing
reported here were standard systems for
measuring 02, CO, S02, NO, and N02.
The focus of this verification test was on
the NO and N02 measurement
capabilities.
Figure 2-1. COSA 7000 Vario Plus Analyzer
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Chapter 3
Test Design and Procedures
3.1 Introduction
The verification test described in this report was conducted in May 2000. The test was conducted
at Battelle in Columbus, Ohio, according to procedures specified in the Test/QA Plan for
Verification of Portable NO/NO2 Emission Analyzer s.m Verification testing of the analyzers
involved the following tests:
1. A series of laboratory tests in which certified NO and N02 standards were used to
challenge the analyzers over a wide concentration range under a variety of conditions.
2. Tests using three realistic combustion sources, in which data from the analyzers
undergoing testing were compared to chemiluminescent NO and NOx measurements
made following the guidelines of EPA Method 7E.(2)
The schedule of tests conducted on the COS A Instruments 7000 Vario Plus analyzers is shown in
Table 3-1.
Table 3-1. Identity and Schedule of Tests Conducted on COSA Instruments 7000
Vario Plus Analyzers
Test Activity Date Conducted
Laboratory Tests
Linearity
May
15,
2000, p.m.
Interrupted Sampling
May
15,
p.m. - May 16, a.m
Interferences
May
16,
a.m.
Pressure Sensitivity
May
16,
a.m.
Ambient Temperature
May
16,
p.m.
Combustion Source Tests
Gas Rangetop
May
17,
a.m.
Gas Water Heater
May
17,
a.m.
Diesel Generator-High RPM
May
18,
a.m.
Diesel Generator-Idle
May
18,
a.m.
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To assess inter-unit variability, two identical 7000 Vario Plus analyzers were tested simul-
taneously. These two analyzers were designated as Unit A and Unit B throughout all testing. The
7000 Vario Plus analyzers were operated at all times by a representative of COS A Instruments so
that each analyzer's performance could be assessed without concern about the familiarity of
Battelle staff with the analyzers. At all times, however, the COSA Instruments representative was
supervised by Battelle staff. Displayed NO and N02 readings from the analyzers (in ppm) were
manually entered onto data sheets prepared before the test by Battelle. Battelle staff filled out
corresponding data sheets, recording, for example, the challenge concentrations or reference
analyzer readings, at the same time that the analyzer operator recorded data. This approach was
taken because visual display of measured NO and N02 (or NOx) concentrations was the "least
common denominator" of data transfer among several NO/NOz analyzers tested.
Verification testing began with COSA Instruments staff setting up and checking out their two
analyzers in the laboratory at Battelle. Once vendor staff were satisfied with the operation of the
analyzers, the laboratory tests were begun. These tests were carried out in the order specified in
the test/QA plan.(1) Upon completion of laboratory tests, the analyzers were moved to a nearby
building where the combustion sources described below were set up, along with two chemi-
luminescent nitrogen oxides monitors which served as the reference analyzers. The combustion
source tests were conducted indoors, with the gas combustion source exhausts vented through the
roof of the test facility. The diesel engine was located immediately outside the wall of the test
facility; sampling probes ran from the analyzers located indoors through the wall to the diesel
exhaust duct. This arrangement assured that testing was not interrupted and that no bias in testing
was introduced as a result of the weather. Sampling of source emissions began with the com-
bustion source emitting the lowest NOx concentration and proceeded to sources emitting
progressively more NOx. In all source sampling, the analyzers being tested sampled the same
exhaust gas as did the reference analyzers. This was accomplished by inserting the 7000 Vario
Plus analyzers' gas sampling probes into the same location in the exhaust duct as the reference
analyzers' probe.
3.2 Laboratory Tests
The laboratory tests were designed to challenge the analyzers over their full nominal response
ranges, which for the 7000 Vario Plus analyzers were 0 to 2,000 ppm for NO and 0 to 1,000 ppm
for N02. These nominal ranges greatly exceed the actual NO or N02 concentrations likely to be
emitted from most combustion sources. Nevertheless, the laboratory tests were aimed at
quantifying the full range of performance of the analyzers.
Laboratory tests were conducted using certified standard gases for NO and N02, and a gas
dilution system with flow calibrations traceable to the National Institute of Standards and
Technology (NIST). The NO and N02 standards were diluted in high purity gases to produce a
range of accurately known concentrations. The NO and N02 standards were EPA Protocol 1
gases, obtained from Scott Specialty Gases, of Troy, Michigan. As required by the EPA
Protocol® the concentration of these gas standards was established by the manufacturer within
1% accuracy using two independent analytical methods. The concentration of the NO standard
(Scott Cylinder Number ALM 057210) was 3,925 ppm, and that of the N02 standard (Scott
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Cylinder Number ALM 031907) was 512 ppm. These standards were identical to NO and N02
standard cylinders used in the combustion source tests, which were confirmed near the end of the
verification test by comparison with independent standards obtained from other suppliers.
The gas dilution system used was an Environics Model 4040 mass flow controlled diluter (Serial
Number 2469). This diluter incorporated four separate mass flow controllers, having ranges of
10, 10, 1, and 0.1 1pm, respectively. This set of flow controllers allowed accurate dilution of gas
standards over a very wide range of dilution ratios, by selection of the appropriate flow con-
trollers. The mass flow calibrations of the controllers were checked against a NIST standard by
the manufacturer prior to the verification test, and were programmed into the memory of the
diluter. In verification testing, the Protocol Gas concentration, inlet port, desired output con-
centration, and desired output flow rate were entered by means of the keypad of the personal
computer used to operate the 4040 diluter, and the diluter then set the required standard and
diluent flow rates to produce the desired mixture. The 4040 diluter indicated on the computer
display the actual concentration being produced, which in some cases differed very slightly from
the nominal concentration requested. In all cases the actual concentration produced was recorded
as the concentration provided to the analyzers undergoing testing. The 4040 diluter also provided
warnings if a flow controller was being operated at less than 10% of its working range, i.e., in a
flow region where flow control errors might be enhanced. Switching to another flow controller
then minimized the uncertainties in the preparation of the standard dilutions.
Dilution gases used in the laboratory tests were Acid Rain CEM Zero Air and Zero Nitrogen
from Scott Specialty Gases. These gases were certified to be of 99.9995% purity, and to have
the following maximum content of specific impurities: S02 <0.1 ppm, NOx <0.1 ppm,
CO < 0.5 ppm, C02 < 1 ppm, total hydrocarbons <0.1 ppm, and water < 5 ppm. In addition the
nitrogen was certified to contain less than 0.5 ppm of oxygen, while the air was certified to
contain 20 to 21% oxygen.
Laboratory testing was conducted primarily by supplying known gas mixtures to the analyzers
from the Environics 4040 diluter, using a simple manifold that allowed the two analyzers to
sample the same gas. The experimental setup is shown schematically in Figure 3-1. The manifold
itself consisted of a 9.5-inch length of thin-walled 1-inch diameter 316 stainless steel tubing, with
1/4-inch tubing connections on each end. The manifold had three 1/4-inch diameter tubing side
arms extending from it: two closely spaced tubes are the sampling points from which sample gas
was withdrawn by the two analyzers, and the third provided a connection for a Magnehelic
differential pressure gauge (±15 inches of water range) that indicated the manifold pressure
relative to the atmospheric pressure in the laboratory. Gas supplied to the manifold from the
Environics 4040 diluter always exceeded by at least 0.5 1pm the total sample flow withdrawn by
the two analyzers. The excess vented through a "T" connection on the exit of the manifold, and
two coarse needle valves were connected to this "T," as shown in Figure 3-1. One valve con-
trolled the flow of gas out the normal exit of the manifold, and the other was connected to a small
vacuum pump. Closing the former valve elevated the pressure in the manifold, and opening the
latter valve reduced the pressure in the manifold. Adjustment of these two valves allowed
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Figure 3-1. Manifold Test Setup
close control of the manifold pressure within a target range of ±10 inches of water, while main
taining excess flow of the gas mixtures to the manifold. The arrangement shown in Figure 3-1
was used in all laboratory tests, with the exception of interference testing. For most interference
testing, gas standards of the appropriate concentrations were supplied directly to the manifold,
without use of the Environics 4040 diluter.
Laboratory testing consisted of a series of separate tests evaluating different aspects of analyzer
behavior. The procedures for those tests are described below, in the order in which the tests were
actually conducted. The statistical procedures that were applied to the data from each test are
presented in Chapter 5 of this report. Before starting the series of laboratory tests, the 7000
Vario Plus analyzers were calibrated with 100 and 1,000 ppm NO, and with 250 and 500 ppm
N02, prepared by diluting the EPA Protocol Gases using the Environics 4040 diluter.
3.2.1 Linearity
Linearity testing consisted of a wide-range 21-point response check for NO, and for N02. At the
start of this check, the 7000 Vario Plus analyzers sampled the appropriate zero gas and then an
NO or N02 concentration near 2,000 ppm NO or 500 ppm N02. The actual concentrations were
2,000 ppm NO and 512 ppm N02. The 21-point check then proceeded without any adjustments
to the analyzers. The 21 points consisted of three replicates each at 10, 20, 40, 70, and 100% of
the concentrations stated above, in randomized order, and interspersed with six replicates of zero
gas.(1) Following completion of all 21 points, the zero and 100% points were repeated, also
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without adjustment of the analyzers. This entire procedure was performed for NO and then for
N02. Throughout the linearity test, the analyzer indications of both NO and N02 concentrations
were recorded, even though only NO or N02 was supplied to the analyzers. This procedure
provided data to assess the cross-sensitivity to NO and N02.
3.2.2 Detection Limit
Data from zero gas and from the 10% concentration points in the linearity test were used to
establish the NO and N02 detection limits of the analyzers, using a statistical procedure defined
in the test/QA plan.(1)
3.2.3 Response Time
During the NO and N02 linearity tests, upon switching from zero gas to an NO or N02
concentration of 70% of the maximum level used (i.e., about 1,400 ppm NO or 350 ppm N02),
the analyzers' responses were recorded at 10-second intervals until fully stabilized. These data
were used to determine the response times for NO and for N02, defined as the time to reach 95%
of final response after switching from zero gas to the calibration gas.
3.2.4 Interrupted Sampling
After the zero and span checks that completed the linearity test, the 7000 Vario Plus analyzers
were shut down (i.e., their electrical power was turned off overnight), ending the first day of
laboratory testing. The next morning the analyzers were powered up, and the same zero gas and
span concentrations were run without adjustment of the analyzers. Comparison of the NO and
N02 zero and span values before and after shutdown indicated the extent of zero and span drift
resulting from the shutdown. Levels of 2,000 ppm NO and 512 ppm N02 were used as the span
values in this test.
3.2.5 Interferences
Following analyzer startup and completion of the interrupted sampling test, the second day of
laboratory testing continued with interference testing. This test evaluated the response of the
7000 Vario Plus analyzers to species other than NO and N02. The potential interferants listed in
Table 3-2 were supplied to the analyzers one at a time, and the NO and N02 readings of the
analyzers were recorded. The potential interferants were used one at a time, except for a mixture
of S02 and NO, which was intended to assess whether S02 in combination with NO produced a
bias in NO response.
The CO, C02, S02, and NH3 used in the interference test were all obtained as Certified Master
Class Calibration Standards from Scott Technical Gases, at the concentrations indicated in
Table 3-2. The indicated concentrations were certified by the manufacturer to be accurate within
± 2%, based on analysis. The CO, C02, and NH3 were all in ultra-high purity (UHP) air, and the
S02 was in UHP nitrogen. The S02/NO mixture listed in Table 3-2 was prepared by diluting the
NO Protocol Gas with the S02 standard using the Environics 4040 diluter.
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Table 3-2. Summary of Interference Tests Performed
Interferant
Interferant Concentration
CO 496 ppm
C02 5.03%
S02 501 ppm
NH3 494 ppm
Hydrocarbon Mixture® 465 ppm Cx, 94 ppm C2,
46 ppm C3 + C4
S02 and NO 451 ppm S02 + 393 ppm NO
Cj = methane; C2 = ethane; and C3 + C4 = 23 ppm propane + 23 ppm n-butane.
The hydrocarbon interferant listed in Table 3-2 was prepared at Battelle in UHP hydrocarbon-
free air, starting from the pure compounds. Small quantities of methane, ethane, propane, and
n-butane were injected into a cylinder that was then pressurized with UHP air. The required
hydrocarbon concentrations were approximated by the preparation process, and then quantified
by comparison with a NIST-traceable standard containing 1,020 ppm carbon (ppmC) in the form
of propane. Using a gas chromatograph with a flame ionization detector (FID) the NIST-traceable
standard was first analyzed. The resulting FID response factor (2,438 area units/ppmC) was then
used to determine the concentrations of the components of the prepared hydrocarbon mixture.
Two analyses of that mixture gave results of 463 and 467 ppm methane; the corresponding
results for ethane were 93 and 95 ppm; for propane 22 and 23 ppm; and for n-butane 23 and
23 ppm.
In the interference test, each interferant in Table 3-2 was provided individually to the sampling
manifold shown in Figure 3-2, at a flow in excess of that required by the two analyzers. Each
period of sampling an interferant was preceded by a period of sampling the appropriate zero gas.
3.2.6 Pressure Sensitivity
The pressure sensitivity test was designed to quantify the dependence of analyzer response on the
pressure in the sample gas source. By means of two valves at the downstream end of the sample
manifold (Figure 3-1), the pressure in the manifold could be adjusted above or below the ambient
room pressure, while supplying the manifold with a constant ppm level of NO or N02 from the
Environics 4040 diluter. This capability was used to determine the effect of the sample gas
pressure on the sample gas flow rate drawn by the analyzers, and on the NO and N02 response.
The dependence of sample flow rate on pressure was determined using an electronically timed
bubble flow meter (Buck Primary Flow Calibrator, Model M5, Serial No. 051238; SKC, Inc.).
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This flow meter was connected in line (i.e., inserted) into the sample flow path from the manifold
to one of the commercial analyzers. Zero gas was supplied to the manifold at ambient pressure,
and the analyzer's sample flow rate was measured with the bubble meter. The manifold pressure
was then adjusted to -10 inches of water relative to the room, and the analyzer's flow rate was
measured again. The manifold pressure was adjusted to +10 inches of water relative to the room,
and the flow rate was measured again. The bubble meter was then moved to the sample inlet of
the other commercial analyzer, and the flow measurements were repeated.
The dependence of NO and N02 response on pressure was determined by sampling the
appropriate zero gas, and an NO or N02 span gas, at each of the same manifold pressures (room
pressure, -10 inches, and +10 inches). This procedure was conducted simultaneously on both
analyzers, first for NO at all three pressures, and then for N02 at all three pressures. The data at
different pressures were used to assess zero and span drift resulting from the sample pressure
differences.
3.2.7 Ambient Temperature
The purpose of the ambient temperature test was to quantify zero and span drift that may occur as
the analyzers are subjected to different temperatures during operation. This test involved pro-
viding both analyzers with zero and span gases for NO and N02 (at the same concentrations used
in the pressure sensitivity test) at room, elevated, and reduced temperatures. A temperature range
of about 7 to 40°C (45 to 105 °F) was targeted in this test. The elevated temperature condition
was achieved using a 1.43 m3 steel and glass laboratory chamber, heated using external heat
lamps. The reduced temperature condition was achieved using a commercial laboratory
refrigerated cabinet (Lab Research Products, Inc.).
The general procedure was to provide zero and span gas for NO, and then for N02, to both
analyzers at room temperature, and then to place both analyzers and the sampling manifold into
the heated chamber. Electrical and tubing connections were made through a small port in the
lower wall of the chamber. A thermocouple readout was used to monitor the chamber tempera-
ture and room temperature, and the internal temperature indications of the analyzers themselves
were monitored, when available. After 1 hour or more of stabilization in the heated chamber, the
zero and span tests were repeated. The analyzers, manifold, and other connections were then
transferred to the refrigerator. After a stabilization period of 1 hour or more, the zero and span
checks were repeated at the reduced temperature. The analyzers were returned to the laboratory
bench; and, after a 1-hour stabilization period, the zero and span checks were repeated a final
time.
3.3 Combustion Source Tests
3.3.1 Combustion Sources
Three combustion sources (a gas rangetop, a gas residential water heater, and a diesel engine)
were used to generate NOx emissions from less than 10 ppm to over 300 ppm. Emissions
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databases for two of these sources (rangetop and water heater) exist as a result of prior
measurements, both of which have been published.(4,5)
3.3.1.1 Rangetop
The low-NOx source was a residential natural gas fired rangetop (KitchenAid Model 1340),
equipped with four cast-iron burners, each with its own onboard natural gas and combustion air
control systems. The burner used (front-left) had a fixed maximum firing rate of about 8 KBtu/hr.
The rangetop generated NO in the range of about 5 to 8 ppm, and N02 in the range of about 1 to
3 ppm. The database on this particular appliance was generated in an international study in which
15 different laboratories, including Battelle, measured its NO and N02 emissions.(4)
Rangetop NOx emissions were diluted prior to measurement using a stainless-steel collection
dome, fabricated according to specifications of the American National Standards Institute (ANSI
Z21.1).(6) For all tests, this dome was elevated to a fixed position 2 inches above the rangetop
surface. Moreover, for each test, a standard "load" (pot) was positioned on the grate of the
rangetop burner. This load was also designed according to ANSI Z21.1 specifications regarding
size and material of construction (stainless steel). For each test, the load contained 5 pounds of
room-temperature water.
The exit of the ANSI collection dome was modified to include seven horizontal sample-probe
couplers. One of these couplers was 1/4-inch in size, three were 3/8-inch in size, and three were
1/2-inch in size. These were available to accommodate various sizes of vendor probes, and one
reference probe, simultaneously during combustion-source sampling.
This low-NOx combustion source was fired using "standard" natural gas, obtained from Praxair,
Inc., which was certified to contain 90% methane, 3% ethane, and the balance nitrogen. This
gaseous fuel contained no sulfur.
3.3.1.2 Water Heater
The medium-NOx source was a residential natural gas-fired water heater (Ruud Model P40-7) of
40-gallon capacity. This water heater was equipped with one stamped-aluminum burner with its
own onboard natural gas and combustion air control systems, which were operated according to
manufacturer's specifications. The burner had a fixed maximum firing rate of about 40 KBtu/hr.
Gas flow to the water heater was monitored using a calibrated dry-gas meter.
The water heater generated NO emissions in the range approximately 50 to 80 ppm, and N02 in
the range of 4 to 8 ppm. NOx emissions dropped as the water temperature rose after ignition,
stabilizing at the levels noted above. To assure constant operation of the water heater, a con-
tinuous draw of 3 gpm was maintained during all verification testing. The database on this
particular appliance was generated in a national study in which six different laboratories
measured its emissions, including Battelle.®
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Water heater N0X emissions were not diluted prior to measurement. The draft hood, integral to
the appliance, was replaced with a 3-inch diameter, 7-inch long stainless-steel collar. The exit of
this collar was modified to include five horizontal sample-probe couplers. One coupler was
1/4-inch in size, whereas the two other pairs were either 3/8- or 1/2-inch in size. Their purpose
was to hold two vendor probes and one reference probe simultaneously during sampling. This
medium-NOx combustion source was fired on house natural gas, which contained odorant-level
sulfur (approximately 4 ppm mercaptan).
3.3.1.3 Diesel Engine
The high-NOx source was an industrial diesel 8 kW electric generator (Miller Bobcat 225D Plus),
which had a Deutz Type ND-151 two-cylinder engine generating 41 KBtu/hr (16 horsepower).
This device generates N0X emissions over a range of about 200 to 330 ppm, depending on the
load on the super-charged engine. High load (3,500 RPM) resulted in the lowest NOx; idle
operation resulted in the highest NOx. At both conditions, about one-third of the NOx was N02.
Data on diesel generator emissions were generated in tests conducted in the two weeks prior to
the start of the verification test.
NOx emissions from this engine were not diluted prior to measurement. The 1-inch exhaust out-
let of the engine, which is normally merely vented to the atmosphere, was fitted with a stack
designed to meet the requirements of the EPA Method 5.(9) The outlet was first expanded to
2 inches of 1.5-inch diameter copper tubing, then to 15 inches of 2-inch diameter copper tubing,
and finally to 2 inches of 3-inch diameter copper tubing. The 3-inch diameter tubing was modi-
fied to include five horizontal sample-probe couplers. One of these couplers was 1/4-inch in size,
two were 3/8-inch in size, and two were 1/2-inch in size. These couplers held the sample probes
in place. The 3-inch tube was connected to a 3-inch stack extending through the roof of the test
laboratory. This high-NOx combustion source was fired on commercial diesel fuel, which, by
specification, contains only 0.03 to 0.05 weight% sulfur.
3.3.2 Test Procedures
The procedures followed during combustion source testing consisted of those involved with the
sampling systems, reference method, calibration gas supply, and the sources, as follows.
3.3.2.1 Sampling Systems
Prior to sampling, the COSA Instruments representative inserted two of his product's probes into
the exhaust duct of the rangetop, water heater, or diesel engine. The 7000 Vario Plus analyzer
probes were fitted close to each other, sampling from a point within about 1/4 inch of the inlet of
the reference analyzers' probe.
The reference analyzer probe consisted of an 18-inch long, 1/4-inch diameter stainless-steel tube,
the upstream 2 inches of which were bent at a right angle for connection to a stainless steel
bulkhead union in the wall of the exhaust duct. The inner end of the bulkhead union connected to
a short length of 1/4-inch diameter stainless steel tube that extended into the center of the source
11
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exhaust duct. The 7000 Vario Plus analyzers were each operated with their own sample probe
and sample transfer lines, and with the optional sample conditioners to dry and filter the sample.
Based on the results of trial runs conducted before the verification test, neither the reference
sampling probe nor the reference sample-transfer lines were heated. Visible condensation of
combustion-generated water did not occur. The reference analyzer moisture-removal system
consisted of a simple condenser in an ice bath connected to the stainless steel probe by a 2-foot
length of 1/4-inch diameter Teflon® tubing. The downstream end of the condenser was
connected by a 3-foot length of 1/4-inch Teflon tubing to an inlet "tee" connected to both
reference analyzers. The reference particulate-removal system consisted of a 47-millimeter in-
line quartz fiber filter, which was used in sampling the diesel emissions.
3.3.2.2 Reference Method
The reference method against which the vendor analyzers were compared was the ozone
chemiluminescence method for NO that forms the basis of EPA Method 7E.(2) The reference
measurements were made using two Model 42-C source-level NOx monitors (from Thermo
Environmental Instruments), located on a wheeled cart positioned near the combustion sources.
These monitors sampled from a common intake line, as described above. Both instruments use
stainless steel converters maintained at 650°C (1,202°F) for reduction of N02 to NO for
detection. The two reference analyzers were designated as Unit No. 100643 and 100647,
respectively.
The reference analyzers were calibrated before and after combustion source tests using an
Environics Series 2020 diluter (Serial No. 2108) and EPA Protocol 1 gases for NO and N02
(3,925 ppm, Cylinder No. ALM 15489, and 511.5 ppm, Cylinder No. AAL 5289, respectively;
Scott Specialty Gases). The calibration procedure was specified in the test/QA plan, and required
calibration at zero, 30%, 60%, and 100% of the applicable range value (i.e., 50, 100, or 1,000
ppm, depending on the emission source). Calibration results closest in time to the combustion
source test were used to establish scale factors applicable to the source test data. The conversion
efficiency of the stainless steel converters was determined by calibrating with both NO and N02
on the applicable ranges, using the EPA Protocol 1 gases. The ratio of the linear regression slope
of the N02 calibration to that of the NO calibration determined the N02 conversion efficiency.
For the COSA Instruments source tests, which took place on May 17 and 18, 2000, calibration
data from May 15 were applied. Conversion efficiency values of 91.7 and 100% were found for
the two reference analyzers, and all reference data were corrected for those conversion
efficiencies.
3.3.2.3 Calibration Gas Supply
Before and after sampling of each combustion source, both the analyzers undergoing testing and
the reference analyzers were supplied with zero gas and with standard NO and N02 mixtures at
levels comparable to those expected from the source. To prepare these mixtures, Protocol 1 gases
identical to those used in the laboratory testing were diluted using an Environics Series 2020
Multi-Gas Calibrator (Serial Number 2108). The same Acid Rain CEM zero gases were used for
12
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dilution and zeroing as were used in the laboratory tests. The pre- and post-test span values used
with each combustion source are given in Table 3-3.
Table 3-3. Span Concentrations Provided Before and After Each Combustion Source
Source
NO Span Level (ppm)
N02 Span Level (ppm)
Gas Rangetop
20
10
Gas Water Heater
100
15
Diesel-High RPM
200
50
Diesel-Idle
400
100
The pre- and post-test zero and span values were used to assess the drift in zero and span
response of the tested analyzers caused by exposure to source emissions.
3.3.2.4 Operation of Sources
Verification testing was conducted with the combustion sources at or near steady-state in terms
of NOx emission. For the rangetop, steady-state was achieved after about 15 minutes, when the
water began to boil. For the water heater, steady-state was achieved in about 15 minutes, when its
water was fully heated. Because the water heater tank had a thermostat, cycling would have
occurred had about 3 gpm of hot water not been continuously drained out of the tank.
For the diesel engine, steady-state was achieved in about 10 minutes of operation. The diesel
engine was operated first at full speed (3,500 RPM) to achieve its lowest NOx emissions. Prior to
sampling the NOx emissions at idle, the diesel engine was operated at idle for about 20 minutes
to effectively "detune" its performance.
The order of operation of the combustion sources was (1) rangetop, (2) water heater, (3) diesel
engine (high RPM), and (4) diesel engine (idle). This allowed the analyzers to be exposed to
continuously increasing NO and N02 levels, and avoided interference in low level measurements
that might have resulted from prior exposure to high levels.
Sampling of each combustion source consisted of obtaining nine separate measurements of the
source emissions. After sampling of pre-test zero and span gases provided from the calibration
source, and with both the reference and vendor analyzers sampling the source emissions, the
COSA Instruments operator indicated when he was ready to take the first set of readings (a set of
readings consisting of the NO and N02 response on both Units A and B). At that time the
Battelle operator of the reference analyzers also took corresponding readings. The analyzers
undergoing testing were then disconnected from the source, and allowed to sample room air until
readings dropped well below the source emissions levels. The analyzers were then reconnected to
the source, and after stabilizing another set of readings was taken. There was no requirement that
analyzer readings drop fully to zero between source measurements. This process was repeated
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until a total of nine readings had been obtained with both the vendor and reference analyzers. The
same zero and span gases were then sampled again before moving to the next combustion source.
The last operation in the combustion source testing involved continuous sampling of the diesel
engine emissions for a full hour with no intervals of room air sampling. Data were recorded for
both reference and vendor analyzers at 1-minute intervals throughout that hour of measurement.
This extended sampling was conducted only after nine sequential sets of readings had been
obtained from all the combustion sources by the procedure described above. Results from this
extended sampling were used to determine the measurement stability of the 7000 Vario Plus
analyzers.
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Chapter 4
Quality Assurance/Quality Control
Quality control (QC) procedures were performed in accordance with the quality management
plan (QMP) for the AMS Center(7) and the test/QA plan(1) for this verification test.
4.1 Data Review and Validation
Test data were reviewed and approved according to the AMS Center QMP, the test/QA plan, and
Battelle's one-over-one approval policy. The Verification Testing Leader reviewed the raw data
and data sheets that were generated each day. Laboratory record notebooks were also signed and
dated by testing staff and reviewed by the Verification Testing Leader.
Other data review focused upon the compliance of the reference analyzer data with the quality
requirements of Method 7E. The purpose of validating reference data was to ensure usability for the
purposes of comparison with the demonstration technologies. The results of the review of the
reference analyzer data quality are shown in Table 4-1. The data generated by the reference analyzers
were used as a baseline to assess the performance of the technologies for N0/N02 analysis.
4.2 Deviations from the Test/QA Plan
During the physical set up of the verification test, deviations from the test/QA plan were made to
better accommodate differences in vendor equipment and other changes or improvements. Any
deviation required the approval signature of Battelle's Verification Testing Leader and the Center
manager. A planned deviation form was used for documentation and approval of the following
changes:
1. The order of testing was changed in the pressure sensitivity test to require fewer plumbing
changes in conducting the test.
2. The order of the ambient temperature test was changed to maximize the detection of any
temperature effect.
3. The concentrations used in the mixture of S02 and NO for the interference test were changed
slightly.
4. For better accuracy, the oxygen sensor used during combustion source tests was checked by
comparison to an independent paramagnetic 02 sensor, rather than to a wet chemical
measurement.
5. Single points (rather than triplicate points) were run at each calibration level in calibrating
the reference analyzers, in accord with Method 7E.
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Table 4-1. Results of QC Procedures for Reference Analyzers for Testing COSA
Instruments 7000 Vario Plus Analyzers
N02 conversion
efficiency (Unit 100643)
N02 conversion
efficiency (Unit 100647)
Calibration of reference
method using four points
at 0, 30, 60, 100% for
NO
Calibration of reference
method using four points
at 0, 30, 60, 100% for
no2
Calibrations
(100 ppm range)
91.7%
100%
Meets criteria
(r2 = 0.9999)
Meets criteria
(r2 = 0.9999)
Meet + 2% requirement (relative
to span)
Unit 100643
Unit 100647
NO
NO
Error, % of
at % of
Error, % of
at % of
Span
Scale
Span
Scale
0.8
30
0.9
30
0.2
60
0.3
60
no2
no2
Error, % of
at % of
Error, % of
at % of
Span
Scale
Span
Scale
0.4
30
0.6
30
0.1
60
0.2
60
Zero drift
Span drift
Interference check
Meets + 3% requirement (relative
to span) on all combustion
sources
Meets + 3% requirement (relative
to span) on all combustion
sources
< + 2% (no interference response
observed)
6. A short, unheated sample inlet was used with the reference analyzers, based on pre-test trial
runs, on Battelle's previous experience in sampling the combustion sources used in this test,
and on other similar sources.
7. No performance evaluation audit was conducted on the natural gas flow rate measurement
used with the gas water heater. This measurement was made with a newly calibrated dry gas
meter.
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4.3 Calibration of Laboratory Equipment
Equipment used in the verification test required calibration before use, or verification of the
manufacturer's calibrations. Some auxiliary devices were obtained with calibrations from
Battelle's Instrument Laboratory. Equipment types and calibration dates are listed in Table 4-2.
For key equipment items, the calibrations listed include performance evaluation audits (see
Section 4.5.2). Documentation of calibration of the following equipment was maintained in the
test file.
Table 4-2. Equipment Type and Calibration Date
Equipment Type
Gas Dilution System Environics
Model 4040 (Serial Number 2469)
Gas Dilution System Environics
Model 2020 (Serial Number 2108)
Fluke Digital Thermometer
(LN-570068)
Servomex 570A Analyzer
(X-44058)
Dwyer Magnahelic Pressure Gauge
Doric Trendicator 41 OA Thermocouple
Temperature Sensor (Serial Number 331513)
American Meter DTM 115 Dry Gas Meter
(Serial Number 89P124205)
Use
Lab tests
Source tests
Ambient temperature
test
Flue gas 02
Pressure sensitivity test
Flue gas temperature
Gas flow measurement
4.4 Standard Certifications
Standard or certified gases were used in all verification tests, and certifications or analytical data
were kept on file to document the traceability of the following standards:
¦ EPA Protocol Gas Nitrogen Dioxide
¦ EPA Protocol Gas Nitric Oxide
¦ Certified Master Class Calibration Standard Sulfur Dioxide
¦ Certified Master Class Calibration Standard Carbon Dioxide
¦ Certified Master Class Calibration Standard Ammonia
¦ Certified Master Class Calibration Standard Carbon Monoxide
¦ Nitrogen Acid Rain CEM Zero
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¦ Acid Rain CEM Zero Air
¦ Battelle-Prepared Organics Mixture.
All other QC documentation and raw data for the verification test are located in the test file at
Battelle, to be retained for 7 years and made available for review if requested.
4.5 Performance System Audits
Three internal performance system audits were conducted during verification testing. A technical
systems audit was conducted to assess the physical setup of the test, a performance evaluation
audit was conducted to evaluate the accuracy of the measurement system, and an audit of data
quality was conducted on 10% of all data generated during the verification test. A summary of
the results of these audits is provided below.
4.5.1 Technical Systems Audit
A technical systems audit (TSA) was conducted on April 18, 2000, (laboratory testing) and
May 17 and 18, 2000, (source testing) for the N0/N02 verification tests conducted in early 2000.
The TSA was performed by the Battelle's Quality Manager as specified in the AMS Center
Quality Management Plan (QMP). The TSA ensures that the verification tests are conducted
according to the test/QA plan(1) and all activities associated with the tests are in compliance with
the AMS Center QMP(7). All findings noted during the TSA on the above dates were documented
and submitted to the Verification Testing Leader for correction. The corrections were docu-
mented by the Verification Testing Leader and reviewed by Battelle's Quality Manager and
Center Manager. None of the findings adversely affected the quality or outcome of this verifi-
cation test and all were resolved to the satisfaction of the Battelle Quality Manager. The records
concerning the TSA are permanently stored with the Battelle Quality Manager.
4.5.2 Performance Evaluation Audit
The performance evaluation audit was a quantitative audit in which measurement standards were
independently obtained and compared with those used in the verification test to evaluate the
accuracy of the measurement system. That assessment was conducted by Battelle testing staff on
May 26, 2000, and the results were reviewed by independent QA personnel.
The most important performance evaluation (PE ) audit was of the standards used for the
reference measurements in source testing. The PE standards were NO and N02 calibration gases
independent of the test calibration standards that contained certified concentrations of NO and
N02. Accuracy of the reference analyzers was determined by comparing the measured N0/N02
concentrations using the verification test standards with those obtained using the certified PE
standards. Percent difference was used to quantify the accuracy of the results. The PE sample for
NO was an EPA Protocol Gas having a concentration (3,988 ppm) nearly the same as the NO
standard used in verification testing, but purchased from a different commercial supplier
(Matheson Gas Products). The PE standard for N02 was a similar commercial standard of
463 ppm N02 in air, also from Matheson. Table 4-3 summarizes the N0/N02 reference standard
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Table 4-3. Performance Evaluation Results
Reference
Standard
Analyzer
Reading on
Diluted Standard
Apparent
Concentration3
Percent
Differenceb
Acceptance
Limits
Unit 100643
Test Std
PE Std
NO in N2
(ppm)
3,925
3,988
98.8 ppm
100.6 ppm
3,917 ppm
0.2%
±2%
Unit 100647
Test Std
PE Std
NO in N2
(ppm)
3,925
3,988
99.6 ppm
101.4 ppm
3,917 ppm
0.2%
±2%
Unit 100643
Test Std
PE Std
N02 in Air
(ppm)
511.5
463
44.2 ppm
42.5 ppm
482 ppm
5.8%
±5%
Unit 100647
Test Std
PE Std
N02 in Air
(ppm)
511.5
463
49.6 ppm
48.8 ppm
471ppm
7.9%
±5%
Concentration of Test Standard indicated by comparison to the Performance Evaluation Standard; i.e., Apparent
Concentration = (Test Std. Reading/PE Std. Reading) x PE Std. Cone.; e.g., Apparent Concentration = 98.8/100.6
x 3,988 ppm = 3,917 ppm.
Percent difference of Apparent Concentration relative to Test Standard concentration; e.g., percent difference =
3,925 ppm - 3,917 ppm
3,925 ppm
X 100= 0.2%.
performance evaluation results. Included in this table are the performance acceptance ranges and
the certified gas concentration values. The acceptance ranges are guidelines established by the
provider of the PE materials to gauge acceptable analytical results.
Table 4-3 shows that the PE audit confirmed the concentration of the Scott 3,925 ppm NO test
standard almost exactly: the apparent test standard concentration was within 0.2% of the test
standard's nominal value. On the other hand, the PE audit results for the Scott 511.5 ppm N02
standard were not as close. The comparison to the Matheson PE standard indicated that the
511.5 ppm N02 Scott standard was only about 480 ppm, a difference of about 7% from its
nominal value. This result suggests an error in the Scott test standard for N02. However, a
separate line of evidence indicates that the Matheson PE standard is likely in error. Specifically,
conversion efficiency checks on the reference analyzers (performed by comparing their responses
to the Scott NO and N02 standards) consistently showed the efficiency of the converter in 42-C
Unit 100647 to be very close to 100%. This finding could not occur if the concentration of the
N02 standard were low. That is, a conversion efficiency of 100% indicates agreement between
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the NO standard and the N02 standard; and, as shown in Table 4-3, the NO standard is confirmed
by the PE comparison. Thus, the likelihood is that the Matheson PE standard was in fact some-
what higher in concentration than its nominal 463 ppm value.
PE audits were also done on the 02 sensor used for flue gas measurements, and on the
temperature indicators used for ambient and flue gas measurements. The PE standard for 02
was an independent paramagnetic sensor, and for temperature was a certified mercury-in-glass
thermometer. The 02 comparison was conducted during sampling of diesel exhaust; the tempera-
ture comparisons were conducted at room temperature. The results of those audits are shown in
Table 4-4, and indicate close agreement of the test equipment with the PE standards.
4.5.3 Audit of Data Quality
The audit of data quality is a qualitative and quantitative audit in which data and data handling
are reviewed and data quality and data usability are assessed. Audits of data quality are used to
validate data at the frequency of 10% and are documented in the data audit report. The goal of an
audit of data quality is to determine the usability of test results for reporting technology
performance, as defined during the design process. Validated data are reported in the ETV
verification reports and ETV verification statement along with any limitations on the data and
recommendations for limitations on data usability.
The Battelle Quality Manager for the verification test audited 10% of the raw data. Test data
sheets and laboratory record books were reviewed, and statistical calculations and other
algorithms were verified. Calculations that were used to assess the four-point calibration of the
reference method were also verified to be correct. In addition, data presented in the verification
report and statement were audited to ensure accurate transcription.
Table 4-4. Performance Evaluation Results in 02 and Temperature Measuring Equipment
Analyzer
Reading
Difference
Acceptance Limits
Servomex 570A 02
18.9% 02
0% 02
—
PE Standard®
18.9% 02
Fluke Digital Thermometer
22.1°C
0.1°C
2% absolute T
PE Standard15
22°C
Doric 410A Temp. Sensor
24.8°C
0.2°C
2% absolute T
PE Standard15
25.0°C
0.2°C
a Independent paramagnetic 02 analyzer.
b Certified mercury-in-glass thermometer.
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Chapter 5
Statistical Methods
5.1 Laboratory Tests
The analyzer performance characteristics were quantified on the basis of statistical comparisons
of the test data. This process began by converting the spreadsheet files that resulted from the data
acquisition process into data files suitable for evaluation with Statistical Analysis System (SAS)
software. The following statistical procedures were used to make those comparisons.
5.1.1 Linearity
Linearity was assessed by linear regression with the calibration concentration as the independent
variable and the analyzer response as the dependent variable. Separate assessments were carried
out for each 7000 Vario Plus analyzer. The calibration model used was
Yc = h(c) + error
where Yc is the analyzer's response to a challenge concentration c, h(c) is a linear calibration
curve, and the error term was assumed to be normally distributed. (If the variability is not
constant throughout the range of concentrations then weighting in the linear regression is
appropriate. It is often the case that the variability increases as the true concentration increases.)
The variability (gc) of the measured concentration values (c) was modeled by the following
relationship,
o2c =a + kc$
where a, k, and p are constants to be estimated from the data. After determining the relationship
between the mean and variability, appropriate weighting was determined as the reciprocal of the
variance.
weight = w c = —
a.
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The form of the linear regression model fitted was h(c) = a0 + a,c. In the concentration sub-
region where the linear calibration model provides a valid representation of the concentration-
response relation, concentration values were calculated from the estimated calibration curve
using the relation
, Y. - a.
c = h \Y) =
ai
A test for departure from linearity was carried out by comparing the residual mean square
1 6 -
—(Y - a - a,c)2n w
A / V c. O 1 V c. c
4 2=1
to an F-distribution with 6-2 = 4 numerator degrees of freedom.
Yci is the average of the nci analyzer responses at the i"1 calibration concentration, q. The
regression relation was fitted to the individual responses; however, only the deviation about the
sample mean analyzer responses at each calibration concentration provide information about
goodness-of-fit.
fl ci n
cij "0 "1 vy ci Z—^ ^ ci ± cif vv ci ' Z—^ cij ^0 ^1^^ ,lciry ci
i=l j=l i=l j=l / = 1
E E (Yen ~ao ~aic)2 wc> = E E Pci - YJ2 wci + E (Xdi ~ao ~aic)2nw.
The first summation on the right side of the equation provides information only about response
variability. The second summation provides all the information about goodness-of-fit to the
straight-line calibration model. This is the statistic that is used for the goodness-of-fit test.
5.1.2 Detection Limit
Limit of detection (LOD) is defined as the smallest true concentration at which an analyzer's
expected response exceeds the calibration curve at zero concentration by three times the standard
deviation of the analyzer's zero reading, i.e., a0 + 3 a0, if the linear relation is valid down to zero.
The LOD may then be determined by
(a + 3a ) - a 3a
LOD =1—2 °- 2J = —°
(Xj (Xj
where a0 is the estimated standard deviation at zero concentration. The LOD is estimated as
LOD =3d0 / ar The standard error of the estimated detection limit is approximately
22
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si: (lod) - Lou
1 [ £g(a,)'
2(/7-l) ^ 3j ;
2
Note that the validity of the detection limit estimate and its standard error depends on the validity
of the assumption that the fitted linear calibration model accurately represents the response down
to zero concentration.
5.1.3 Response Time
The response time of the 7000 Vario Plus analyzers to a step change in analyte concentration was
calculated by determining the total change in response due to the step change in concentration,
and then determining the point in time when 95% of that change was achieved. Using data taken
every 10 seconds, the following calculation was carried out:
Total Response = Rc - Rz
where Rc is the final response of the analyzer to the calibration gas and Rz is the final response of
the analyzer to the zero gas. The analyzer response that indicates the response time then is:
Response95o/o = 0.95 (Total Response) + Rz.
The point in time at which this response occurs was determined by inspecting the response/time
data, linearly interpolating between two observed time points, as necessary. The response time
was calculated as:
RT = Time95o/o - Timej,
where Time950/o is the time at which ResponseRT occurred and Timej is the time at which the span
gas was substituted for the zero gas. Since only one measurement was made, the precision of the
response time was not determined.
5.1.4 Interrupted Sampling
The effect of interrupted sampling is the arithmetic difference between the zero data and between
the span data obtained before and after the test. Differences are stated as ppm. No estimate was
made of the precision of the observed differences.
5.1.5 Interferences
Interference is reported as both the absolute response (in ppm) to an interferant level, and as the
sensitivity of the analyzer to the interferant species, relative to its sensitivity to NO or N02. The
relative sensitivity is defined as the ratio of the observed N0/N02/N0x response of the analyzer
to the actual concentration of the interferant. For example, an analyzer that measures NO is
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challenged with 500 ppm of CO, resulting in an absolute difference in reading of 1 ppm (as NO).
The relative sensitivity of the analyzer is thus 1 ppm/500 ppm = 0.2%. The precision of the
interference results was not estimated from the data obtained, since only one measurement was
made for each interferant.
5.1.6 Pressure Sensitivity
At each of ambient pressure, reduced pressure (-10 inches of water), and increased pressure
(+10 inches of water), the analyzer flow rate, the response on zero gas, and the response on span
gas were measured for each analyzer. Variability in zero and span responses for reduced and
increased pressures was assumed to be the same as the variability at ambient pressure. The
variability determined in the linearity test was used for this analysis. The duct pressure effects on
analyzer flow rates and response were assessed by separate linear regression trend analyses for
flow rate and for response. The precision of the pressure effects on zero concentration response
and on span gas response was estimated based on the variability observed in the linearity test.
Statistical significance of the trends across duct pressures was determined by comparing the
estimated trends to their estimated standard errors, based on two-tailed t-tests:
t = (0.040825
-------
5.2 Combustion Source Tests
5.2.1 Accuracy
The relative accuracy (RA) of the analyzers with respect to the reference method is expressed as:
RA = = x 100%
x
where Prefers to the difference between the average of the two reference analyzers and one of the
tested units and ^corresponds to the average of the two reference analyzer values. Sd denotes the
sample standard deviation of the differences, based on n = 9 samples, while tan4 is the t value for
the 100(1 - a)th percentile of the distribution with n - 1 degrees of freedom. The relative accuracy
was determined for an a value of 0.025 (i.e., 97.5% confidence level, one-tailed). The RA cal-
culated in this way can be determined as an upper confidence bound for the relative bias of the
analyzer \j\jx > where the bar indicates the average value of the differences or of the reference
values.
Assuming that the reference method variation is due only to the variation in the output source
and the true bias between the test and reference methods is close to zero, an approximate
standard error for RA is
SE -
5,
Jnx ^
0.3634 + f,
73-1
2(n-l)
x 100%
5.2.2 Zero/Span Drift
Statistical procedures for assessing zero and span drift were similar to those used to assess
interrupted sampling. Zero (span) drift was calculated as the arithmetic difference between zero
(span) values obtained before and after sampling of each combustion source. The same calcula-
tion was also made using zero and span values obtained before and after the linearity and ambient
temperature tests. No estimate was made of the precision of the zero and span drift values.
5.2.3 Measurement Stability
The temporal stability of analyzer response in extended sampling from a combustion source was
assessed by means of a trend analysis on 60 minutes of data obtained continuously using the
diesel generator as the source. The existence of a difference in trend between the test unit and the
average of the reference units was assessed by fitting a linear regression line with the difference
between the measured concentration for a test unit and the average of the reference units as the
dependent variable, and time as the independent variable. Subtracting the average reference unit
25
-------
values adjusts for variation in the source output. The slope and the standard error of the slope are
reported. The null hypothesis that the slope of the trend line on the difference is zero was tested
using a one-sample two-tailed t-test with n - 2 = 58 degrees of freedom.
5.2.4 Inter- Unit Repeatability
The purpose of this comparison was to determine if any significant differences in performance
exist between two identical analyzers operating side by side. In tests in which analyzer per-
formance was verified by comparison with data from the reference method, the two identical
units of each type of analyzer were compared to one another using matched pairs t-test
comparisons. In tests in which no reference method data were obtained (e.g., linearity test), the
two 7000 Vario Plus analyzer units were compared using statistical tests of difference. For
example, the slopes of the calibration lines determined in the linearity test, and the detection
limits determined from those test data, were compared. Inter-unit repeatability was assessed for
the linearity, detection limit, accuracy, and measurement stability tests.
For the linearity test, the intercepts and slopes of the two units were compared to one another by
two-sample t-tests using the pooled standard error, with combined degrees of freedom the sum of
the individual degrees of freedom.
For the detection limit test, the detection limits of the two units were compared to one another by
two-sample t-tests using the pooled standard error with 10 degrees of freedom (the sum of the
individual degrees of freedom).
For the relative accuracy test, repeatability was assessed with a matched-pairs two-tailed t-test
with n - 1 = 8 degrees of freedom.
For the measurement stability test, the existence of differences in trends between the two units
was assessed by fitting a linear regression to the paired differences between the units. The null
hypothesis that the slope of the trend line on the paired differences is zero was tested using a
matched-pairs t-test with n - 2 = 58 degrees of freedom.
5.2.5 Data Completeness
Data completeness was calculated as the percentage of possible data recovered from an analyzer
in a test; the ratio of the actual to the possible number of data points, converted to a percentage,
i.e.,
Data Completeness = (Na)/(Np) x 100%,
where Na is the number of actual and Np the number of planned data points.
26
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Chapter 6
Test Results
6.1 Laboratory Tests
6.1.1 Linearity
Tables 6-la and b list the data obtained in the linearity tests for NO and N02, respectively. The
response of both the NO and N02 sensors in each analyzer is shown in those tables.
Table 6-2 shows the results of the linear calibration curve fits for each unit and each analyte,
based on the data shown in Tables 6-la and b.
Table 6-la. Data from NO Linearity Test of COSA Instruments 7000 Vario Plus Analyzers
Actual NO
Unit A NO
Unit A N02
Unit B NO
Unit B N02
Reading
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
1
0
0
1
0
2
2
2000
1931
20
1945
19
3
200
205
7
205
7
4
800
806
7
809
7
5
0
2
3
2
3
6
1400
1386
3
1394
3
7
420
427
4
429
4
8
200
202
3
202
3
9
0
3
2
2
2
10
420
426
3
428
3
11
800
806
4
810
4
12
1400
1389
7
1397
7
13
0
3
2
2
2
14
2000
1934
9
1952
9
15
1400
1385
6
1396
7
16
800
807
5
812
5
17
0
3
2
3
3
18
420
428
3
429
3
19
200
202
2
203
3
20
2000
1935
7
1952
8
21
0
3
2
3
2
27
-------
Table 6-lb. Data from N02 Linearity Test of COSA Instruments 7000 Vario Plus Analyzers
Actual N02 Unit A NO
Unit A N02
Unit B NO
Unit B NO,
Number
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
1
0
0
0
0
0
2
512
2
511
2
508
3
50
0
53
0
53
4
200
0
201
0
200
5
0
0
2
0
2
6
350
0
353
0
350
7
105
0
108
0
108
8
50
0
52
0
52
9
0
0
2
0
2
10
105
0
106
0
106
11
200
0
201
0
200
12
350
1
353
1
350
13
0
0
2
0
3
14
512
2
516
2
512
15
350
1
356
1
353
16
200
0
205
0
204
17
0
0
2
0
3
18
105
0
107
0
106
19
50
0
52
0
52
20
512
2
516
3
512
21
0
0
2
0
3
Table 6-2. Statistical Results for Test of Linearity
Unit A
Unit B
Linear Regression
NO
no2
NO
no2
Intercept (ppm) (Std Err)
7.306 (3.128)
1.784 (0.268)
6.104 (2.598)
2.719 (0.759)
Slope (Std Err)
0.975 (0.004)
1.003 (0.002)
0.984 (0.004)
0.993 (0.002)
r2
0.9997
0.9999
0.9997
0.9999
The results in Table 6-2 show that the N02 response of the 7000 Vario Plus analyzers was linear
over the entire range tested of up to 512 ppm. The N02 slopes are 0.99 to 1.00, and the r2 values
are 0.9999.
The NO linearity results in Table 6-2 show that over the tested range of up to 2,000 ppm NO, the
7000 Vario Plus analyzers gave slopes of about 0.98. Inspection of the NO linearity data shows
28
-------
that the slope of the NO response is essentially 1.0 at all concentrations tested, except for a
slightly low response at the 2,000 ppm point. For example, the regression slopes for the two
7000 Vario Plus units are 0.991 and 0.997 when only the lowest 18 calibration points in
Table 6-la (i.e., up to 1,400 ppm) are included. These results indicate that the linear range of NO
response for the 7000 Vario Plus analyzers is at least 1,500 ppm, with possibly a slight downturn
in response at levels approaching 2,000 ppm.
The data in Tables 6-la and 6-lb also indicate the extent of cross-sensitivity of the COSA NO
and N02 sensors. Regression of the 7000 Vario Plus N02 responses in the NO linearity test
(Table 6-la) gives the following results:
Unit A N02 = 0.0042 x(NO, ppm) + 2.0 ppm, with r2 = 0.531, and
Unit B N02 = 0.0040 x (NO, ppm) + 2.3 ppm, with r2 = 0.566.
These results indicate a very slight response of the COSA N02 sensors to NO, amounting to
about 0.4% of the NO level present.
Similarly, regression of the 7000 Vario Plus NO responses in the N02 linearity test (Table 6-lb)
gives the following results:
Unit A NO = 0.0035 X(N02, ppm) - 0.23 ppm, with r2 = 0.762, and
Unit B NO = 0.0040 x(N02, ppm) - 0.27 ppm, with r2 = 0.718.
These results also indicate a very small response of the COSA NO sensors to N02, amounting to
about 0.4% of the N02 level present.
6.1.2 Detection Limit
Table 6-3 shows the estimated detection limits for each test unit and each analyte, determined
from the data obtained in the linearity test. These detection limits apply to the calibrations
conducted over a 0 to 2,000 ppm range for NO (Table 6-la) and a 0 to 512 ppm range for N02
(Table 6-lb).
Table 6-3. Estimated Detection Limits for COSA Instruments 7000 Vario Plus Analyzers3
Unit A
Unit B
NO
NO,
NO
no2
Estimated Detection Limit (ppm)
3.7
2.4
3.3
3.5
(Standard Error) (ppm)
(1.2)
(0.8)
(1-1)
(1-1)
a Results are based on calibrations over 0 to 2,000 ppm range for NO and 0 to 512 ppm range for NOz.
29
-------
Table 6-3 displays the estimated detection limits, and their standard errors for NO and N02,
separately for each 7000 Vario Plus analyzer. NO detection limits of 3 to 4 ppm, and N02
detection limits of 2 to 4 ppm, are indicated. It must be stressed that these detection limits are
based on the zero gas responses, interspersed with sampling high levels of NO and N02 in the
linearity tests.
6.1.3 Response Time
Table 6-4 lists the data obtained in the response time test of the 7000 Vario Plus analyzers.
Table 6-5 shows the response times of the analyzers to a step change in analyte concentration,
based on the data shown in Table 6-4. The observed response times were consistent, at 37
seconds for NO, and about 80 seconds for N02.
Table 6-5 shows that the 4-minute time response criterion generally required of portable N0/N02
analyzers.®
6.1.4 Interrupted Sampling
Table 6-6 shows the zero and span data resulting from the interrupted sampling test, and
Table 6-7 shows the differences (pre- minus post-) of the zero and span values. Span con-
centrations of 2,000 ppm NO and 512 ppm N02 were used for this test.
Table 6-7 shows that changes in zero readings for both NO and N02 were only a few ppm. These
small changes in zero reading indicate good stability of the analyzers, and probably result from
the exposure to elevated NO and N02 levels in the linearity tests that immediately preceded the
shutdown. That is, the small decreases in zero readings are probably the result of the analyzers
returning to baseline readings after the linearity tests.
The 7000 Vario Plus analyzers showed no change in the N02 span response as a result of the
shutdown (Table 6-7). The changes observed in the NO span response are negligible, amounting
to, at most, 0.2% of the 2,000 ppm NO span value.
6.1.5 Interferences
Table 6-8 lists the data obtained in the interference tests. Table 6-9 summarizes the sensitivity of
the analyzers to interferant species, based on the data from Table 6-8. The results in Table 6-8
use the average of the zero readings before and after the interferant exposure to calculate the
extent of the interference.
30
-------
Table 6-4. Response Time Data for COSA Instruments 7000 Vario Plus Analyzers
Unit A NO
Unit A N02
Unit B NO
Unit B N02
Time (sec)
(ppm)
(ppm)
(ppm)
(ppm)
0
2
2
2
2
10
3
4
2
4
20
389
97
397
79
30
1233
226
1212
209
40
1360
283
1372
272
50
1375
310
1387
300
60
1379
324
1390
316
70
1381
331
1392
325
80
1382
336
1393
329
90
1383
339
1394
333
100
1384
341
1393
335
110
1385
342
1394
337
120
1384
343
1394
339
130
1386
344
1394
340
140
1385
345
1394
341
150
1385
346
1395
341
160
1386
346
1395
342
170
1386
347
1395
343
180
1385
347
1394
343
190
1386
348
1394
344
200
348
344
210
348
345
220
349
345
230
349
345
240
349
345
250
349
346
260
350
346
270
350
346
280
350
347
290
350
347
300
351
347
31
-------
Table 6-5. Response Time Results for COSA Instruments 7000 Vario Plus Analyzers
Unit A
Unit B
NO
no2
NO
no2
Response Time (sec)a
37
75
37
82
a The analyzer's responses were recorded at 10-second intervals; therefore the point in time when the 95%
response was achieved was determined by interpolating between recorded times to the nearest second.
Table 6-6. Data from Interrupted Sampling Test with COSA Instruments 7000 Vario Plus
Analyzers
Unit A NO
Unit A N02
Unit B NO
Unit B NO,
Pre-Shutdown Date:
05/15/2000
Time:
17:15
Pre-Shutdown Zero (ppm):
3
2
3
3
Pre-Shutdown Span (ppm):
1934
516
1950
512
Post-Shutdown Date:
05/16/2000
Time:
8:15
Post-Shutdown Zero (ppm):
0
0
0
0
Post-Shutdown Span (ppm):
1935
516
1946
512
Table 6-7. Pre- to Post-Test Differences as a Result of Interruption of Operation of COSA
Instruments 7000 Vario Plus Analyzers
Unit A
Unit B
Pre-Shutdown—Post-Shutdown
NO
no2
NO
no2
Zero Difference (ppm)
3
2
3
3
Span Difference (ppm)
-1
0
4
0
32
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Table 6-8. Data from Interference Tests on COS A Instruments 7000 Vario Plus Analyzers
Interferant
Interferant, Cone.
Response (ppi
m equivalent)
Gas
(ppm)
Unit A NO
Unit A N02
Unit B NO
Unit B N02
Zero
0
2
0
2
CO
496
0
2
0
2
Zero
0
1
0
1
co2
5.03%
0
1
0
1
Zero
0
1
0
1
nh3
494
0
0
0
0
Zero
0
0
0
0
HCs
605
0
0
0
1
Zero
0
0
0
0
so2
501
0
0
0
0
Zero
0
0
0
0
S02 + NO
451 + 393
399
0
399
0
Table 6-9. Results of Interference Tests of COSA Instruments 7000 Vario Plus Analyzers
Unit A Response ppm Unit B Response ppm
(relative sensitivity, %) (relative sensitivity, %)
Interferant NO N02 NO N02
CO (496 ppm)
0
0.1%
0
0.1%
C02 (5.03%)
0
0
0
0
NH3 (494 ppm)
0
-0.1%
0
-0.1%
HCs (605 ppm)
0
0
0
0.2%
S02 (501 ppm)
0
0
0
0
S02 (451 ppm) +
NO (393 ppm)
1.33%
0
1.33%
0
Table 6-9 indicates that there were no significant interference effects from CO, C02, NH3, HCs,
and S02 or from S02 in the presence of NO. The response to 393 ppm NO was barely increased
by the presence of 451 ppm S02.
6.1.6 Pressure Sensitivity
Table 6-10 lists the data obtained in the pressure sensitivity test. Table 6-11 summarizes the
findings from those data in terms of the ppm differences in zero and span readings at the different
duct gas pressures and the ccm differences in analyzer flow rates at the different duct gas
pressures.
33
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Tables 6-10 and 6-11 show that only very small changes in 7000 Vario Plus zero and span
readings resulted from the changes in duct pressure, for both NO and N02. Average zero
readings changed by less than 1 ppm, and span readings changed by no more than 8 ppm for NO
(0.4 % of the 2,000 ppm span level) and 10 ppm for N02 (2% of the 512 ppm span level). The
changes observed do not indicate any statistically significant effect of pressure on zero or span
readings.
Tables 6-10 and 6-11 do show a small effect of pressure on the sample flow rates of the 7000
Vario Plus analyzers. The reduced pressure condition reduced the flow rates by 4 to 6%, and the
increased pressure condition increased the flow rates by 8 to 15%, relative to the flows at
ambient pressure.
Table 6-10. Data from Pressure Sensitivity Test for COSA Instruments 7000 Vario Plus
Analyzers
Pressure
Unit A NO
Unit A N02
Unit B NO
Unit B N02
Ambient
Flow rate (ccm)
1664
1664
1555
1555
Zero (ppm)
0
0
0
0
NO span (ppm)
1944
5
1955
5
Zero (ppm)
1
1
0
1
N02 span (ppm)
8
505
8
510
Zero (ppm)
0
3
0
3
+ 10 in. H20
Flow rate (ccm)
1807
1807
1787
1787
Zero (ppm)
0
0
0
0
NO span (ppm)
1948
4
1963
5
Zero (ppm)
1
1
0
1
N02 span (ppm)
8
514
7
513
Zero (ppm)
0
2
0
3
-10 in. H20
Flow rate (ccm)
1560
1560
1489
1489
Zero (ppm)
1
0
0
1
NO span (ppm)
1946
4
1961
4
Zero (ppm)
1
1
0
1
N02 span (ppm)
8
515
8
512
Zero (ppm)
0
2
0
3
34
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Table 6-11. Pressure Sensitivity Results for COS A Instruments 7000 Vario Plus Analyzers
Unit A Unit B
NO
no2
NO
no2
Zero
High-Ambient (ppm diff1)
0
-0.333
0
0
Low-Ambient (ppm diff)
0.334
-0.333
0
0.334
Significant Pressure Effect
N
N
N
N
Span
High-Ambient (ppm diff)
4
9
8
3
Low-Ambient (ppm diff)
2
10
6
2
Significant Pressure Effect
N
N
N
N
Flow
High-Ambient (ccm diff*)
143
232
Rate
Low-Ambient (ccm diff)
-104
-66
a ppm or ccm difference between high/low and ambient pressures. The differences were calculated based on the
average of the zero values.
6.1.7 Ambient Temperature
Table 6-12 lists the data obtained in the ambient temperature test with the 7000 Vario Plus
analyzers. Table 6-13 summarizes the sensitivity of the analyzers to changes in ambient
temperature.
Tables 6-12 and 6-13 show that the temperature variations in this test had no significant effect on
the N02 zero readings of either 7000 Vario Plus analyzer. However, a significant temperature
effect was indicated for the NO zero readings. This result is almost entirely due to the slightly
elevated NO zero readings observed when the analyzers were placed in the heated chamber
(Table 6-12).
Temperature did have a significant effect on the NO and N02 span responses of both 7000 Vario
Plus analyzers, but the consistency of the effects is different for NO and N02. A small but
significant effect was seen for NO, with warmer environments giving higher span values. The
total difference in span readings between cool and heated environments was about 2.5% of the
2,000 ppm NO span value. In contrast, the effect was not consistent for N02. Unit A showed a
lower N02 span response in the heated environment, and a higher response in the cooled environ-
ment, than at room temperature. The Unit A N02 response was markedly high in the cooled
environment (Table 6-12). Unit B showed slightly lower response at the heated condition,
relative to room temperature. These results do not strongly show a consistent temperature effect
for N02.
35
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Table 6-12. Data from Ambient Temperature Test of COSA Instruments 7000 Vario Plus
Analyzers
Unit A NO
Unit A N02
Unit B NO
Unit B N02
Condition
(ppm)
(ppm)
(ppm)
(ppm)
(Room Temp.)
Temp. 25.6°C (78°F)
Zero
0
2
0
2
NO span
1948
16
1959
16
Zero
0
2
0
2
N02 span
8
515
8
511
(Heated)
Temp. 39.4°C (103°F)
Zero
5
1
6
0
NO span
1976
8
1988
8
Zero
8
1
8
1
N02 span
20
506
24
495
(Cooled)
Temp. 7.2°C (45°F)
Zero
0
3
0
3
NO span
1930
27
1935
26
Zero
0
0
0
0
N02 span
7
554
8
509
(Room Temp.)
Temp. 22.8°C (73°F)
Zero
0
1
0
1
NO span
1932
12
1951
12
Zero
1
1
1
1
N02 span
12
514
12
509
36
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Table 6-13. Ambient Temperature Effects on COSA Instruments 7000 Vario Plus
Analyzers
Unit A Unit B
NO NO2 NO N02
Zeroa Heat-Room (ppm diff1) 6.25 -0.5 6.75 -1
Cool-Room (ppm diff) -0.25 0 -0.25 0
Significant Temp Effect Y N Y N
Spana Heat-Room (ppm diff) 36 -8.5 33 -15
Cool-Room (ppm diff) -10 39.5 -20 -1
Significant Temp. Effect Y Y Y Y
a ppm difference between heated/cooled and room temperatures. The differences were calculated using the
average of two recorded responses at room temperature (Table 6 12).
6.1.8 Zero/Span Drift
Zero and span drift were evaluated from data taken at the start and end of the linearity and
ambient temperature tests. Those data are shown in Table 6-14, and the drift values observed are
shown as pre- minus post-test differences in ppm in Table 6-15. Table 6-15 shows that zero drifts
in these tests were 3 ppm or less for both NO and N02 on both 7000 Vario Plus analyzers. Zero
drifts were less than 1 ppm in the temperature test, but were slightly larger in the linearity test,
probably because of the elevated zero readings caused by the exposures to high NO and N02
levels. Span drift for N02 amounted to 5 ppm or less (about 1% of the 512 ppm span value).
Span drift for NO amounted to 16 ppm or less (less than 1% of the 2,000 ppm NO span value).
Table 6-14. Data from Linearity and Ambient Temperature Tests Used to Assess Zero and
Span Drift of the COSA Instruments 7000 Vario Plus Analyzers
Test
Unit A NO
(ppm)
Unit A N02
(ppm)
Unit B NO
(ppm)
Unit B N02
(ppm)
Linearity Pre-TestZero
0
0
0
0
Pre-Test Span
1931
511
1945
508
Post-Test Zero
3
2
3
3
Post-Test Span
1934
516
1950
512
Ambient Temperature Pre-TestZero
0
2
0
2
Pre-Test Span
1948
515
1959
511
Post-Test Zero
0
1
0
1
Post-Test Span
1932
514
1951
509
37
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Table 6-15. Zero and Span Drift Results for the COS A Instruments 7000 Vario Plus
Analyzers
Unit A
Unit B
NO
no2
NO
no2
Pre- and Post-Differences
(ppm)
(ppm)
(ppm)
(ppm)
Linearity Test
Zero
-3
-2
-3
-3
Span
-3
-5
-5
-4
Ambient Temperature Test
Zero
-0.5
1
-0.5
1
Span
16
1
8
2
6.2 Combustion Source Tests
6.2.1 Relative Accuracy
Tables 6-16a through d list the measured NO, N02, and NOx data obtained in sampling the four
combustion sources. Note that the 7000 Vario Plus analyzers measure NO and N02, and the
indicated NOx readings are the sum of those data. On the other hand, the reference analyzers
measure NO and NOx, with N02 determined by difference.
Table 6-17 displays the relative accuracy (in percent) for NO, N02, and NOx of Units A and B
for each of the four sources. Estimated standard errors are shown with the relative accuracy
estimates. These standard error estimates were calculated under the assumption of zero true bias
between the reference and test methods. If the bias is in fact non-zero, the standard errors
underestimate the variability.
Table 6-17 shows that relative accuracy for NOx ranged from 2.8 to 10.7% over both analyzers
and all combustion sources. Relative accuracy for NO ranged from 2.2 to 18.9%, and the relative
accuracy for N02 ranged from 7.6 to 17.4%. Interestingly, relative accuracy was generally better
at lower concentrations. This finding appears to result primarily because the 7000 Vario Plus
analyzers report NO values 10 to 20% higher than do the reference analyzers with the diesel
source, but not with the gas combustion sources. The unit-to-unit repeatability of the COSA
analyzers was often better than that of the two reference analyzers, indicating highly consistent
performance.
The unit-to-unit agreement of the two 7000 Vario Plus analyzers in source sampling was also
good. For example, the differences between the average NOx values obtained by Units A and B in
the four combustion sources ranged from 0.0 to 1.9%, relative to the average NOx values. In
comparison, the corresponding agreement for the two reference analyzers ranged from 1.2 to
5.9%, and the agreement of the two COSA analyzers was better in all combustion tests than that
of the reference analyzers. These results indicate a high degree of consistency in the performance
of the 7000 Vario Plus analyzers on combustion sources.
38
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39
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Table 6-16c. Data from Diesel Generator at High RPM in Verification Testing of COSA Instruments 7000 Vario Plus Analyzers
COSA Instruments Analyzer Data
Reference Analyzer Data
Unit A
Unit B
Unit 100643
Unit 100647
NO
no2
NOx
NO
no2
NOx
NO
no2
NOx
NO
no2
NOx
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
1
145
51
196
152
62
214
130.2
66.0
196.3
130.3
72.0
202.3
2
148
60
208
149
61
210
129.9
63.6
193.5
132.3
72.0
204.3
3
158
58
216
159
60
219
135.6
61.6
197.2
138.3
67.9
206.2
4
150
59
209
152
60
212
131.6
63.7
195.3
136.3
68.9
205.2
5
145
57
202
146
58
204
128.9
61.9
190.8
132.0
68.8
200.8
6
148
56
204
147
58
205
125.1
61.8
186.9
130.7
67.3
197.9
7
144
57
201
146
57
203
121.5
61.7
183.1
126.1
68.0
194.1
8
146
57
203
148
57
205
124.0
59.5
183.5
127.9
67.8
195.7
9
140
56
196
142
57
199
123.6
57.4
181.1
127.4
66.0
193.4
O
Table 6-16d. Data from Diesel Generator at Idle in Verification Testing of COSA Instruments 7000 Vario Plus Analyzers
COSA Instruments Analyzer Data
Reference Analyzer Data
Unit A
Unit B
Unit 100643
Unit 100647
NO
no2
NOx
NO
no2
NOx
NO
no2
NOx
NO
no2
NOx
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
1
200
85
285
198
82
280
166.4
82.8
249.2
172.3
82.3
254.6
2
198
81
279
197
80
277
167.3
86.0
253.3
175.4
93.6
269.0
3
199
85
284
198
83
281
168.2
87.1
255.3
174.3
96.7
271.1
4
198
86
284
197
85
282
163.5
89.2
252.7
170.3
97.7
268.1
5
194
86
280
195
83
278
160.7
88.1
248.8
168.3
96.7
265.0
6
195
86
281
195
84
279
159.7
86.0
245.7
167.3
95.7
263.0
7
175
86
261
176
83
259
145.6
84.9
230.5
151.3
94.7
246.0
8
170
84
254
171
82
253
142.7
86.0
228.7
149.3
94.7
243.9
9
162
86
248
163
84
247
132.3
84.9
217.3
138.3
94.7
232.9
-------
Table 6-17. Relative Accuracy of COS A Instruments 7000 Vario Plus Analyzers
Unit A
Unit B
NO
no2
NOx
NO
no2
NOx
Source
(%)
(%)
(%)
(%)
(%)
(%)
Gas Rangetop
2.226a
7.556
2.834
2.226
7.556
2.834
(7 ppm NO, 2 ppm N02)c
(0.514)b
(1.589)
(0.541)
(0.514)
(1.589)
(0.541)
Gas Water Heater
4.833
14.061
4.178
4.833
14.061
4.178
(75 ppm NO, 5 ppm NOz)
(0.255)
(3.720)
(0.165)
(0.255)
(3.720)
(0.165)
Diesel Generator-High RPM
15.216
17.410
6.724
16.590
11.127
7.759
(130 ppm NO, 65 ppm NOz)
(0.592)
(1.558)
(0.756)
(0.562)
(0.455)
(0.388)
Diesel Generator-Idle
18.927
8.462
10.711
18.698
10.415
9.574
(160 ppm NO, 90 ppm N02)
(0.443)
(1.012)
(0.520)
(0.385)
(0.871)
(0.431)
a Relative accuracy, percent relative to mean of two reference analyzers.
b Standard error of the relative accuracy value.
0 Approximate NO and N02 levels from each source are shown; see Tables 6-16a through d.
6.2.2 Zero/Span Drift
Table 6-18 shows the data from the combustion source tests used to evaluate zero and span drift
of the 7000 Vario Plus analyzers. Table 6-19 summarizes the zero and span drift results, showing
that zero and span drift was never more than a few ppm in any of the combustion source tests, for
either NO or N02, with either analyzer. The zero drift values exceeded ± 1 ppm only for the NO
response of both 7000 Vario Plus analyzers with the diesel generator at idle. Those NO zero drift
values with the diesel source are less than 1% of the 400 ppm NO span value.
The span drift values in Table 6-19 are similarly very small. Relative to the respective span
values, the NO span drift was at most 1% of span (relative to the 200 ppm span value used with
the diesel at high RPM), and the N02 span drift was at most 4% (relative to the 100 ppm span
value used with the diesel at idle).
41
-------
Table 6-18. Data Used to Assess Zero and Span Drift for COSA Instruments 7000 Vario
Plus Analyzers on Combustion Sources
Source
Unit A NO
(ppm)
Unit A N02
(ppm)
Unit B NO
(ppm)
Unit B N02
(ppm)
Gas Rangetop
Pre-Test Zero
0
0
0
0
Pre-Test Span
20
9
20
9
Post-Test
Zero
0
0
0
0
Post-Test
Span
20
9
20
9
Gas Water Heater
Pre-Test Zero
0
0
0
0
Pre-Test Span
104
14
104
14
Post-Test
Zero
0
0
0
0
Post-Test
Span
104
14
104
14
Diesel-High RPM
Pre-Test Zero
0
0
0
0
Pre-Test Span
209
45
209
45
Post-Test
Zero
1
0
1
0
Post-Test
Span
211
43
211
43
Diesel-Idle
Pre-Test Zero
1
0
1
0
Pre-Test Span
425
86
425
86
Post-Test
Zero
4
0
4
0
Post-Test
Span
427
82
427
84
42
-------
Table 6-19. Results of Zero and Span Drift Evaluation for COSA Instruments 7000 Vario
Plus Analyzers
Unit A
Unit B
Pre-Test—
NO
no2
NO
no2
Post-Test
(ppm)
(ppm)
(ppm)
(ppm)
Gas Rangetop
Zero
0
0
0
0
Span
0
0
0
0
Gas Water Heater
Zero
0
0
0
0
Span
0
0
0
0
Diesel Generator-High RPM
Zero
-1
0
-1
0
Span
-2
2
-2
2
Diesel Generator-Idle
Zero
-3
0
-3
0
Span
-2
4
-2
2
6.2.3 Measurement Stability
Table 6-20 shows the data obtained in the extended sampling test, in which the 7000 Vario Plus
and reference analyzers sampled diesel emissions for a full hour without interruption or sampling
of ambient air. Table 6-21 shows the results of this evaluation, in terms of the slopes and
standard errors of the NO, N02, and NOx data with time. Also shown in Table 6-21 is an
indication of whether the slopes observed by the 7000 Vario Plus analyzers differed from those
observed by the reference analyzers.
Table 6-21 shows that both the 7000 Vario Plus analyzers and the reference analyzers determined
increasing trends in NO and NOx, and a decreasing trend in N02, during the extended sampling
of the diesel source. Most of the trends indicated by the 7000 Vario Plus analyzers were signifi-
cantly different from those indicated by the reference analyzers. However, the actual difference in
the measured trends was very small. For example the NOx slopes determined by 7000 Vario Plus
Units A and B were 0.151 ppm/min (9.1 ppm/hr) and 0.115 ppm/min (6.9 ppm/hr), respectively,
compared to the reference analyzer trend of 0.023 ppm/min (1.4 ppm/hr). Thus, over a one-hour
period the different trends resulted in a 7.7 ppm or less deviation from the trend of the reference
analyzers, or about 3% of the NOx level in the diesel exhaust.
43
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45
-------
Table 6-21. Results of Evaluation of Measurement Stability for COS A Instruments 7000
Vario Plus Analyzer
NO
Unit A
no2
NOx
NO
Unit B
no2
NOx
Reference Units
NO N02 NOx
Slope
0.239
-0.089
0.151
0.216
-0.101
0.115
0.172 -0.149 0.023
(Std Err)
(0.045)
(0.023)
(0.029)
(0.046)
(0.020)
(0.034)
(0.036) (0.023) (0.017
Difference in
Slopes (ppm/min)
0.068
0.060
0.128
0.045
0.047
0.092
(Std Err)
(0.025)
(0.011)
(0.024)
(0.025)
(0.014)
(0.028)
a Statistically significant difference in slope among test unit and the averages of the reference units at the 5%
significance level.
6.2.4 Inter- Unit Repeatability
The repeatability of test results between the two 7000 Vario Plus analyzers was assessed in those
cases where the data lent themselves to application of a t-test. The resulting t-statistics and
associated p-values are listed in Table 6-22. Highlighted in bold are those p-values less than 0.05,
which indicate a statistically significant difference between the two 7000 Vario Plus units at the
95% confidence level. As Table 6-22 shows, statistically significant differences were found
primarily in the areas of relative accuracy and measurement stability.
The differences shown in Table 6-22 indicate the variability that may be expected from one
analyzer to the next. Although some statistically significant differences were found, nevertheless
the practical importance of these differences is often small. Considering the relative accuracy
results, for example (Table 6-17), it is apparent that statistically significant differences may exist
even when the two analyzers are equally applicable to the measurement at hand. For example, the
relative accuracy result for NOx for Unit A on the diesel at idle is 10.7%, whereas that for Unit B
is 9.6%. These results may differ significantly in the statistical sense, but either unit would be
more than adequate for determining NOx emissions from that source. The fine degree of
discrimination provided by the statistical tests should not obscure the fact that the two 7000
Vario Plus analyzers essentially worked equally well throughout the verification tests.
46
-------
Table 6-22. Summary of Repeatability
Unit A vs. Unit B
NO
no2
NOx
Linear Regression
Intercept
t-statistic
0.296
-1.162
—
p-value a
0.774
0.272
—
Slope
t-statistic
-1.716
3.162
—
p-value
0.117
0.010
—
Detection Limit
t-statistic
0.246
-0.803
—
p-value
0.808
u
0.428
u
u
Relative Accuracy
Gas Rangetop
t-statistic
D
D
D
p-value
b
b
b
Gas Water Heater
t-statistic
p-value
-
-
-
Generator-High
t-statistic
2.639
1.859
2.268
RPM
p-value
0.030
0.100
0.053
Generator-Idle
t-statistic
0.286
8.102
5.547
p-value
0.782
<0.001
<0.001
Measurement
Slope
t-statistic
3.480
1.540
3.500
Stability
p-value
0.001
0.130
<0.001
a p-value <0.05 indicates that two test units are statistically different at the 5% significance level (in bold text).
b Unit A and Unit B indicated exactly the same readings. No matched-pairs t-statistic was calculated.
6.3 Other Factors
In addition to the performance characteristics evaluated in the laboratory and combustion source
tests, three additional factors were recorded: analyzer cost, data completeness, and maintenance/
operational factors.
6.3.1 Cost
The cost of each analyzer as tested in this verification test was about $12,000.
6.3.2 Data Completeness
The data completeness in the verification test was 100% for both units of the COS A Instruments
7000 Vario Plus.
6.3.3 Maintenance/Operational Factors
The short duration of the verification test prevented assessment of long-term maintenance costs,
durability, etc., but no maintenance was required and no problems were encountered with the
7000 Vario Plus analyzers in this test. The analyzers appeared to be rugged, and the stability of
the analyzers allowed verification testing to proceed smoothly.
47
-------
Chapter 7
Performance Summary
The COSA Instruments 7000 Vario Plus analyzers provided linear response for N02 over the
tested range of 0 to 512 ppm. Response for NO was linear over the range of 0 to at least
1,500 ppm, but showed a slightly low response at the maximum tested level of 2,000 ppm. Over
the full tested range of 0 to 2,000 ppm NO, the regression slope of NO response was approxi-
mately 0.98. Detection limits estimated from these wide-range linearity tests were 3 to 4 ppm for
NO and 2 to 4 ppm for N02. Response times were 37 seconds for NO and about 80 seconds for
no2.
Drift in 7000 Vario Plus zero readings before and after source combustion and laboratory tests
was within ±2 ppm in nearly all circumstances. In laboratory tests, span drift for NO and N02
was always less than 1% of the respective 2,000 ppm NO and 512 ppm N02 span levels. In
sampling of gas combustion and diesel sources, NO span drift was always less than 1%, and N02
span drift always less than 4%, of the respective span levels. No interference was found from any
of the following: 496 ppm CO; 5.03% C02; 494 ppm NH3; 605 ppm of total hydrocarbons; 501
ppm of S02; or 451 ppm S02 in the presence of 393 ppm NO.
Over the tested range of +10 to -10 in. H20, sample gas pressure had no significant effect on
7000 Vario Plus zero or span readings. Reduced pressure lowered the analyzers' sample flow
rates by about 5%, and positive pressure increased the flow rates by up to 15%. Variations in
ambient temperature over the range of 7 to 39°C (45 to 103°F) had no consistent effect on the
7000 Vario Plus zero or span readings for N02. For NO, this temperature range caused a change
in zero readings of about 6 ppm and a difference in span response of at most 2.5% relative to the
2,000 ppm span gas concentration provided. Both NO zero readings and span response increased
with increasing temperature.
The relative accuracy of the COSA 7000 Vario Plus analyzers for NOx ranged from 2.8 to 10.7%
over both analyzers and all combustion sources. Relative accuracy for NO ranged from 2.2 to
18.9%, and the relative accuracy for N02 ranged from 7.6 to 17.4%. Relative accuracy was
generally better at lower concentrations. This finding appears to result primarily because the NO
values were 10 to 20% higher than the reference analyzers with the diesel source, but not with the
gas combustion sources. At concentrations below 10 ppm, the 7000 Vario Plus analyzers were
accurate within their 1 ppm measurement resolution. Unit-to-unit agreement of the two 7000
Vario Plus analyzers for NOx ranged from 0.0 to 1.9% and was better than that of the two
reference analyzers. Comparison of verification results from the two 7000 Vario Plus analyzers
showed only slight differences, primarily in relative accuracy. Overall, the performance of the
two analyzers was essentially identical.
48
-------
Chapter 8
References
1. Test/QA Plan for Verification of Portable NO/NO2 Emission Analyzers, Version 2.0,
Battelle, Columbus, Ohio, August 1999.
2. U.S. EPA Method 7E Determination of Nitrogen Oxides Emissions from Stationary Sources
(Instrumental Analyzer Procedure) Code of Federal Regulations, 40 CFR, Ch 1, Part 60,
Appendix A (1991).
3. Traceability Protocol for Establishing True Concentrations of Gases Used for Calibrations
and Audits of Continuous Source Emission Monitors: Protocol Number 1, Research
Triangle Park, NC: U.S. Environmental Protection Agency, Quality Assurance Division,
June 1978.
4. Interlaboratory Program to Validate a Protocol for the Measurement of NO2 Emissions
from Rangetop Burners, GRI-94/0458, Gas Research Institute, Chicago, Illinois, December
1994.
5. Interlaboratory Study to Determine the Precision of an Emission Measurement Protocol
for Residential Gas Water Heaters, GRI-96-0021, Gas Research Institute, Chicago, Illinois,
March 1996.
6. American National Standards (ANSI Z21.1) "Household Cooking Gas Appliances,"
American National Standards Institute, 24th Edition, American Gas Association, 1990.
7. Quality Management Plan (QMP) for the ETV Advanced Monitoring Systems Pilot, U.S.
EPA Environmental Technology Verification Program, Battelle, Columbus, Ohio,
September 1998.
8. Portable NOx Analyzer Evaluation for Alternative Nitrogen Oxide Emission Rate
Determination at Process Units, Source Testing and Engineering Branch, South Coast Air
Quality Management District, Los Angeles, CA, September 21, 1994.
9. U.S. EPA Method 5, Determination of Particulate Emissions from Stationary Sources,
Code of Federal Regulations, 40 CFR, Ch. 1, Part 60, Appendix A (1991).
10. Determination of Nitrogen Oxides, Carbon Monoxide, and Oxygen Emissions from Natural
Gas-Fired Engines, Boilers, and Process Heaters Using Portable Analyzers, Conditional
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Test Method (CTM)-030, U.S. EPA, Office of Air Quality Planning and Standards,
Emission Measurement Center, October 13, 1997.
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