July 1999
Environmental Technology
Verification Report
Enerac 3000E
Portable Emission Analyzer
Prepared by
Baffelle
. . , Putting Technology To Wori
Battelle Memorial Institute
Under a cooperative agreement with
U.S. Environmental Protection Agency
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July 1999
Environmental Technology Verification
Report
Advanced Monitoring Systems
Enerac 3000E
Portable Emission Analyzer
By
Thomas Kelly
Ying-Liang Chou
Susan J. Abbgy
Paul I. Feder
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
Development 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 Memorial Institute
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.
Vll
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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 Joseph
Tabor, Steve Speakman, and Joshua Finegold of Battelle, and Bob Gasser of Energy Efficiency
Systems, Inc.
Vlll
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Contents
Notice ii
Foreword vii
Acknowledgments viii
List of Abbreviations xiv
1. Background 1
2. Technology Description 2
3. Test Design and Procedures 4
3.1 Introduction 4
3.2 Laboratory Tests 5
3.2.1 Linearity 7
3.2.2 Detection Limit 8
3.2.3 Response Time 8
3.2.4 Interrupted Sampling 8
3.2.5 Interferences 9
3.2.6 Pressure Sensitivity 10
3.2.7 Ambient Temperature 10
3.3 Combustion Source Tests 11
3.3.1 Combustion Sources 11
3.3.2 Test Procedures 13
4. Quality Assurance/Quality Control 16
4.1 Data Review and Validation 16
4.2 Deviations from the Test/QA Plan 16
4.3 Calibration of Laboratory Equipment 18
4.4 Standard Certifications 18
4.5 Performance System Audits 19
4.5.1 Internal Audits 19
4.5.2 External Audit 22
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5. Statistical Methods 24
5.1 Laboratory Tests 24
5.1.1 Linearity 24
5.1.2 Detection Limit 25
5.1.3 Response Time 26
5.1.4 Interrupted Sampling 26
5.1.5 Interferences 26
5.1.6 Pressure Sensitivity 27
5.1.7 Ambient Temperature 27
5.2 Combustion Source Tests 28
5.2.1 Accuracy 28
5.2.2 Zero/Span Drift 28
5.2.3 Measurement Stability 28
5.2.4 Inter-Unit Repeatability 29
5.2.5 Data Completeness 29
6. Statistical Results 30
6.1 Laboratory Tests 30
6.1.1 Linearity 30
6.1.2 Detection Limit 35
6.1.3 Response Time 36
6.1.4 Interrupted Sampling 36
6.1.5 Interferences 38
6.1.6 Pressure Sensitivity 39
6.1.7 Ambient Temperature 40
6.1.8 Zero and Span Drift 43
6.2 Combustion Source Tests 45
6.2.1 Relative Accuracy 45
6.2.2 Zero and Span Drift 50
6.2.3 Measurement Stability 51
6.2.4 Inter-Unit Repeatability 54
6.3 Other Factors 55
6.3.1 Cost 56
6.3.2 Data Completeness 56
6.3.3 Maintenance/Operational Factors 56
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7. Performance Summary 57
8. References 59
Appendix A: Data Recording Sheets A-l
Appendix B: External Technical Systems Audit Report B-l
Figures
2-1. Enerac 3000E 3
3-1. Manifold Test Setup 7
Tables
3-1. Identity and Schedule of Verification Tests Conducted on Enerac 3000E Analyzers .... 4
3-2. Summary of Interference Tests Performed 9
3-3. Span Concentrations Provided Before and After Each Combustion Source 14
4-1. Results of QC Procedures for Reference NOx Analyzers for Testing
of Enerac 3 000E Analyzers 17
4-2. Equipment Type and Calibration Date 18
4-3. Observations and Findings from the Internal Technical Systems Audit 20
4-4. Performance Evaluation Results 21
6-la. Data from NO Linearity Test over 0-1,000 ppm Range on Enerac 3000E Analyzers ... 31
6-lb. Data from N02 Linearity Test over 0-400 ppm Range on Enerac 3000E Analyzers .... 32
6-lc. Data from NO Linearity Test Over 0-3,000 ppm Range on
Enerac 3000E Analyzers 33
6-ld. Data from NO Linearity Test Over 0-300 ppm Range on
Enerac 3000E Analyzers 34
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6-2a. Statistical Results for First Test of Linearity (NO span = 1000 ppm,
N02 span = 400 ppm) 34
6-2b. Statistical Results for Second Test of Linearity (NO span = 3000 ppm) 35
6-2c. Statistical Results for Third Test of Linearity (NO span = 300 ppm) 35
6-3. Estimated Detection Limits for Enerac 3 000E Analyzers 36
6-4. Response Time Data for Enerac 3000E Analyzers 37
6-5. Response Time Results for Enerac 3000E Analyzers 37
6-6. Data from Interrupted Sampling Test with Enerac 3000E Analyzers 38
6-7. Pre- to Post-Test Differences as a Result of Interruption of Operation of
Enerac 3000E Analyzers 38
6-8. Data from Interference Tests on Enerac 3000E Analyzers 39
6-9. Results of Interference Tests of Enerac 3000E Analyzers 39
6-10. Data from Pressure Sensitivity Test for Enerac 3000E Analyzers 41
6-11. Pressure Sensitivity Results for Enerac 3000E Analyzers 41
6-12. Data from Ambient Temperature Test of Enerac 3000E Analyzers 42
6-13. Ambient Temperature Effects on Enerac 3000E Analyzers 43
6-14. Data from Linearity and Ambient Temperature Tests Used to Assess
Zero and Span Drift of the Enerac 3000E Analyzers 44
6-15. Zero and Span Drift Results for the Enerac 3000E Analyzers 44
6-16a. Data from the Gas Rangetop in Verification Testing of Enerac 3000E Analyzers 46
6-16b. Data from the Gas Water Heater in Verification Testing of Enerac 3000E Analyzers . . 46
6-16c. Data from the Diesel Generator at High RPM in Verification Testing of
Enerac 3000E Analyzers 47
6-16d. Data from Diesel Generator at Idle in Verification Testing of
Enerac 3000E Analyzers 47
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6-17. Relative Accuracy of Enerac 3000E Analyzers 48
6-18. Data Used to Assess Zero and Span Drift for Enerac 3000E Analyzers on
Combustion Sources 50
6-19. Results of Zero and Span Drift Evaluation for Enerac 3000E Analyzers 51
6-20. Data from Extended Sampling Test with Diesel Generator at Idle,
Using Enerac 3000E Analyzer 52
6-21. Results of Evaluation of Measurement Stability for Enerac 3000E Analyzer 54
6-22. Summary of Repeatability 55
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List of Abbreviations
AC
alternating current
AMS
Advanced Monitoring Systems
ANSI
American National Standards Institute
Btu/hr
British thermal unit per hour
ccm
cubic centimeter per minute
CEMS
continuous emission monitoring system
CO
carbon monoxide
co2
carbon dioxide
DC
direct current
EPA
U.S. Environmental Protection Agency
ETV
Environmental Technology Verification
FID
flame ionization detector
ft3
cubic feet
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
02
oxygen
PE
performance evaluation
ppm
parts per million, volume
ppmC
parts per million carbon
QA
quality assurance
QC
quality control
QMP
Quality Management Plan
rms
root-mean-square
RPM
revolutions per minute
SAS
Statistical Analysis System
XIV
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SCAQMD SCAQMD Air Quality Management District
SCR selective catalytic reduction
S02 sulfur dioxide
UHP ultra-high purity
XV
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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 technologies
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 providing 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; with 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 tech-
nologies 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 Memorial Institute, operate the Advanced Monitoring Systems (AMS) program under
ETV. The AMS program 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 Enerac 3000E Portable Emission Analyzer.
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Chapter 2
Technology Description
The objective of the ETV Advanced Monitoring Systems (AMS) pilot is to verify the
performance characteristics of environmental monitoring technologies for air, water, and soil. This
report provides results for verification testing of the Enerac 3000E electrochemical NO and N02
analyzer, manufactured by the Enerac division of Energy Efficiency Systems, Inc., of Westbury,
New York. The following is a description of the Enerac 3000E analyzers, based on information
provided by the vendor.
The Enerac 3000E analyzer integrates advanced electrochemical sensor technology with
automatic quality control features. Key features include
# Automatic NO Temperature Control: The Enerac 3000E's NO sensors are held at a
temperature below 30°C to avoid erroneously overreporting actual NO emissions
# Automatic Sensor/Filter Check: The Enerac 3000E's autocalibration certification
protocol checks and documents both sensor and interference rejection filter performance
during each calibration
# Single Multi-Range Sensors: The Enerac 3000E measures NO concentrations from
10 ppm to over 3,000 ppm.
The Enerac 3000E system measures 18" x 13" x 6" and weighs 22 pounds. The advanced NO
sensor is cooled to a constant temperature by means of a pair of thermoelectric coolers located
below the aluminum plate on which the NO sensor is mounted. The temperature sensor (upper
right hand side of the main sensor body) monitors and controls the temperature of the NO sensor.
Enerac's proprietary precision control modules are placed on the sensor's body to control the
sensor's true range and sensitivity. The same sensor can measure from 10 ppm of NO to 3,000
ppm. The standard nominal ranges of the 3000E are 0 to 1,000 ppm NO and 0 to 500 ppm N02.
Alternative NO ranges provided by the 3000E are 0 to 3,000 ppm and 0 to 300 ppm.
Many low NOx combustion systems can emit a large fraction of the NOx as N02. Some systems
have N02 fractions of over 80 percent, depending on operating conditions. Enerac's battery-
operated permeation dryer can provide effective sample conditioning for such sources.
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The Enerac 3000E also has
advanced two-way communications
via a modem. All performance
parameters can be remotely checked
by the factory.
In the verification test conducted
here, two identical 3000E analyzers
were operated simultaneously in all
testing. The two analyzers were
designated as Unit A and Unit B.
The performance of each unit was
verified separately, and selected test
results were compared to assess
unit-to-unit repeatability.
Figure 2-1. Enerac 3000SEM
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Chapter 3
Test Design and Procedures
3.1 Introduction
The verification test described in this report was conducted in January 1999 on commercial
portable nitrogen oxides analyzers. The tests were conducted at Battelle in Columbus, Ohio,
according to procedures specified in the Test/QA Plan for Verification of Portable NO/NO 2
Emission Analyzers.(l) 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)
These tests are listed in Table 3-1.
Table 3-1. Identity and Schedule of Verification Tests Conducted on Enerac 3000E
Analyzers
Test Activity Date Conducted
Laboratory Tests
Linearity
January
25,
1999, p.m.
Interrupted Sampling
January
25,
1999, p.m. to January 26, 1999, a.m
Interferences
January
26,
a.m.
Pressure Sensitivity
January
26,
p.m.
Ambient Temperature
January
26,
p.m. and January 27, 1999 a.m.
Source Tests
Gas Rangetop January 27, 1999, p.m.
Gas Water Heater January 27, 1999, p.m.
Diesel Generator High RPM January 28, 1999, a.m.
Diesel Generator-Idle January 28, 1999, a.m.
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To assess inter-unit variability, two identical Enerac 3000E analyzers were tested simultaneously.
These two analyzers were designated as Unit A and Unit B throughout all testing. The com-
mercial analyzers were operated at all times by a representative of Enerac 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 Enerac 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 N0/N02 analyzers tested. Copies of the blank data recording sheets used
by Battelle and vendor staff are included as Appendix A of this report.
Verification testing began with Enerac 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 chemiluminescent nitrogen
oxides monitors which served as the reference analyzers. The combustion source tests were
conducted indoors, with the combustion source exhausts vented through the roof of the test
facility. 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 combustion
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 Enerac 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 Enerac 3000E analyzers were 0 to 1,000 ppm for NO and 0 to 500 ppm for
N02. These nominal ranges greatly exceed the actual NO or N02 concentrations likely to be
emitted from most combustion sources. Nevertheless, the lab tests were aimed at quantifying the
full range of performance of the analyzers. Additional laboratory tests were also conducted to
assess the multi-range NO capability of the analyzers using NO ranges of 0 to 3,000 ppm and 0 to
300 ppm.
Laboratory tests were conducted using certified standard gases for NO and N02, and a gas dilu-
tion 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(3) the
concentration of these gas standards was established by the manufacturer within 1 percent accu-
racy 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 Cylinder
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Number ALM 019660) was 493.2 ppm. These concentrations were confirmed in a performance
evaluation audit, conducted near the end of the verification tests, by comparison with independent
standards obtained from other suppliers (see Section 4.5.1.2).
The gas dilution system used was an Environics Model 2020 mass flow controlled diluter (Serial
Number 2108). 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 concen-
tration, and desired output flow rate were entered by means of the front panel keypad of the 2020
diluter, and the diluter then set the required standard and diluent flow rates to produce the desired
mixture. The 2020 diluter indicated on its front panel 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 2020 diluter also provided warnings if a flow controller was
being operated at less than 10 percent 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 percent 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 percent oxygen.
Laboratory testing was conducted primarily by supplying known gas mixtures to the analyzers
from the Environics 2020, 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 2020 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 controlled 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 close control of the
manifold pressure within a target range of ±10 inches of water, while maintaining excess flow of
the gas mixtures to the manifold. The arrangement shown in Figure 3-1 was used
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>• Vent to Hood
Coarse Needle Valves
Vacuum
Pump
Vent to Hood
Differential
P Gauge
Analyzer A
Analyzer B
Zero Gases
(N2 or Air)
Protocol 1
Standards
(NO or N02
Environics
2020 Diluter
Figure 3-1. Manifold Test Setup
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 2020 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.
3.2.1 Linearity
The linearity of analyzer response was tested by wide-range multipoint calibrations with NO and
N02. Linearity testing consisted of a 21-point response check for NO, and for N02. Prior to this
check, the Enerac analyzers were provided with the appropriate zero gas, and then with an NO or
N02 span gas concentration near the respective nominal full scale of the analyzers (i.e., near
1,000 ppm NO or 500 ppm N02). The actual values of the span gases provided were 1,002 ppm
NO and 493.2 ppm N02. However, both analyzers indicated an overrange condition for N02,
even though the 493.2 ppm N02 span gas concentration was within the nominal N02 range of the
analyzers. Since the 493.2 ppm span concentration is within 2 percent of the nominal range, this
occurrence can be readily accounted for by a small difference between the verification standard
and the factory span gas used to set the instrument's upper range. In any case, this overrange
condition was alleviated when the N02 concentration was reduced to 400 ppm, and 400 ppm N02
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was adopted as the span value for the N02 linearity test. After adjustments to the analyzers to
accurately match that span value, the 21-point check proceeded without further adjustments. The
21 points consisted of three replicates each at 10, 20, 40, 70, and 100 percent of the nominal
range, in randomized order, and interspersed with six replicates of zero gas.(1) Following com-
pletion of all 21 points, the zero and 100 percent spans were repeated, also 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 were supplied to the analyzers. This procedure provided data to assess
the cross-sensitivity to NO and N02.
After the linearity tests over ranges of 0 to 1,000 ppm NO and 0 to 400 ppm N02, additional
linearity tests were conducted for NO over ranges of 0 to 3,000 ppm and 0 to 300 ppm. These
were accomplished by changing the control module which sets the sensitivity of the sensor,
thereby changing its range. The additional NO linearity tests followed the same procedure
described above.
It should be noted that a low-range NO control module was used in each Enerac analyzer during
the 0 to 300 ppm NO and 0 to 400 ppm N02 linearity tests, whereas a mid-range NO control
module was used in each analyzer for the 0 to 1,000 ppm and 0 to 3,000 ppm NO linearity tests,
and for all other testing. One feature of the mid-range module is that the analyzers report all
readings below 3 ppm NO as being zero. This feature is intended to prevent users from attempting
to make ambient air NOx measurements. Thus, for the higher NO linearity tests and for all other
testing, the Enerac 3000E analyzers provided no NO response information below 3 ppm.
3.2.2 Detection Limit
Data from zero gas and from 10 percent of full-scale 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 percent of the respective full scale (i.e., about 700 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 percent 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 Enerac 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
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resulting from the shutdown. Near full-scale NO and N02 levels (i.e., 1,000 ppm NO and
400 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
Enerac 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 single components, 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.
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* 485 ppm Cx, 98 ppm C2,
48 ppm C3 + C4
S02 and NO 451 ppm S02 + 385 ppm NO
*C = methane; C2 = ethane; and C3 + C4 = 24 ppm propane + 24 ppm n-butane.
The CO, C02, S02, and NH3 mixtures 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 percent, based on analysis. The CO, C02, and NH3 mixtures were all in Ultra-High Purity
(UHP) air, and the S02 mixture was in UHP nitrogen. The S02/NO mix listed in Table 3-2 was
prepared by diluting the S02 standard with the NO Protocol Gas using the Environics 2020.
The hydrocarbon mixture 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 aNIST standard containing 8.61 ppm carbon (ppmC) in the form of propane.
Using a gas chromatograph with a flame ionization detector (FID) the NIST standard was first
analyzed twice, producing peak areas of 18,627 and 18,791 area units per 8.61 ppmC of propane.
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The average FID response factor (18,709 units (±116 units)/8.61 ppmC) was then used to
determine the concentrations of the components of the prepared hydrocarbon mixture. Two
analyses of that mixture both gave a result of 485 ppm methane; the corresponding results for
ethane were 97 and 98 ppm; for propane 23 and 24 ppm; and for n-butane 24 and 25 ppm.
In the interference test, each interferant in Table 3-2 was provided to the sampling manifold
shown in Figure 3-1, 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 dilution system. 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 (Ultra Flow Primary Gas Flow Calibrator, Model 709, Serial No. 010928;
SKC, Inc.). 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 ana-
lyzer'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 appropri-
ate zero gas, and an NO or N02 span gas of about 700 ppm and 350 ppm, respectively, 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 provid-
ing both analyzers with zero and span gases for NO and N02 (at the same ppm concentrations
used in the pressure test) at room, elevated, and reduced temperatures. A temperature range of
45 to 105°C was targeted in this test. The elevated temperature condition was achieved using a
1.43 m3 steel and glass laboratory chamber, thermostated at 105 °F using external heat lamps. The
reduced temperature condition was achieved using a conventional domestic refrigerator (Crosley
Model CT19A5W) with a refrigerator volume of 13.1 ft3.
10
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The general procedure was to provide zero and span gas for NO, and then for N02, to both ana-
lyzers 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 temperature and
room temperature, and the internal temperature indications of the analyzers themselves were mon-
itored, when available. After 1 hour or more of stabilization in the heated chamber, the zero and
span tests were repeated. The Enerac analyzers were then removed from the heated chamber and
allowed to stabilize while operating at room temperature overnight. The next morning the zero
and span tests were repeated at room temperature. 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.
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 nearly 500 ppm. Emissions
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 4 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
'/2-inch in size. Their purpose was to accommodate various sizes of vendor probes and one
reference probe simultaneously during combustion-source sampling.
11
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This low-NOx combustion source was fired using "standard" natural gas, obtained from Praxair,
Inc., which was certified to contain 90 percent methane, 3 percent 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 of 50 to 70 ppm, and N02 in the range of 5
to 10 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 continuous 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.(5)
Water heater NOx 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 '/2-inch in size. Their purpose was
to accommodate various sizes of 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 (4 ppm mercaptan). The composition of this natural gas is essentially constant, as
monitored by a dedicated gas chromatograph in Battelle's laboratories.
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 generated NOx emissions over a range of about 150 to 450 ppm, depending on the
load on the super-charged engine. High load (3,500 RPM) resulted in the lowest NOx; idle
(2,000 RPM) resulted in the highest NOx. At both conditions, about one-third of the NOx was
N02. The database on the diesel generator emissions was generated in tests conducted in the
2 weeks prior to the start of the verification tests.
NOx emissions from this engine were not diluted prior to measurement. The 1-inch exhaust outlet
of the engine, which is normally merely vented to the atmosphere, was fitted with a stack designed
to meet the requirements of the U.S. 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 modified to include
12
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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 percent 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 Enerac representative inserted two of its product's probes into the exhaust
duct of the rangetop, water heater, or diesel engine. The Enerac probes were fitted one above the
other, sampling from a point within about 1/4 inch of the inlet of the reference analyzers' probe.
Each Enerac probe had a fritted Hastelloy® inlet filter that screwed into the probe tip.
The reference analyzer probe consisted of a 26-inch long, 1/4-inch diameter stainless-steel tube,
the upstream 2 inches of which were bent at a right angle for passage into the center of the source
exhaust duct. Each combustion source had a dedicated sampling probe, connected to the refer-
ence analyzers with 1/4-inch tubing. The lengths of sample-transfer tubing required to connect
vendor instruments to the rangetop, water heater, and diesel engine were about 4 feet, 4 feet, and
8 feet, respectively. The lengths of sample-transfer tubing required to connect reference instru-
ments to the rangetop, water heater, and diesel engine were about 7 feet, 9 feet, and 4 feet,
respectively.
In source testing, the Enerac analyzers were operated with their integral heated sampling probes
and sample conditioning systems. 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 ice bath (0°C). The
reference particulate-removal system consisted of a 47-millimeter in-line quartz fiber filter.
3.3.2.2 Reference Method
The reference method of NO determination 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 a Model 10 and a Model 14A source-level NOx monitor
(both from Thermo Environmental Instruments), located side-by-side near the combustion
sources. These monitors sampled from a common intake line and operated on identical ranges of
100 ppm or 1,000 ppm full scale, depending on the source. Both instruments use stainless steel
catalytic converters maintained at 650°C (1,200°F) for reduction of N02 to NO for detection.
Digital electronic voltmeters were connected directly to the amplifier output of the monitors, to
provide direct digital display of the data. The Model 10 and 14A monitors provide sequential,
rather than simultaneous, measurement of NO and NOx, so display of both readings required
13
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manual switching of sampling modes on both instruments. This requirement resulted in the NO
and NOx readings from the reference analyzers being separated in time by about 15 seconds, due
to the stabilization needed after switching. This effect is believed to have negligible impact on the
verification results due to the stability of source emissions.
The chemiluminescence analyzers were calibrated using the Environics Series 100 and the EPA
Protocol 1 gases (see below). The calibration procedure was specified in the test/QA plan, and
required calibration at zero, 30 percent, 60 percent, and 100 percent of the applicable range value
(i.e., 100 or 1,000 ppm). Calibration results closest in time to the verification 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 cali-
bration to that of the NO calibration determined the N02 conversion efficiency. For the Enerac
source tests, which took place on January 27 and 28, 1999, calibration data from January 26 were
applied. Conversion efficiency values of 85.5 percent and 89.9 percent were found for the Model
14A and Model 10 monitors, respectively. All reference N02 data were corrected to account for
these 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 100
Computerized Multi-Gas Calibrator (Serial Number 2416). The same Acid Rain CEM zero gases
were used for dilution and zeroing as were used in the laboratory tests. When low dilution ratios
were required for some calibration points, Tylan FC-260 (3 1pm) and FC-280 (5 1pm) mass flow
controllers were used instead of the Environics calibrator. The Tylan flow controllers were
calibrated using the same SKC electronic bubble flow meter used in the laboratory tests, and were
operated with a Tylan four-unit control and readout device. 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 reference and analyzers caused by exposure to source emissions.
14
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Before the start of source testing, the Enerac analyzers were first calibrated against 200 ppm NO
and 100 ppm N02 span gases, prepared using the Environics Series 100, as described above. The
span gases listed in Table 3-3 were then sampled before and after sampling the respective
combustion sources.
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 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
Enerac 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 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.
One addition to this procedure was the extended sampling test, conducted as the last operation in
the combustion source testing. This test 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
test was conducted only after nine sequential sets of readings had been obtained from all the
combustion sources by the procedure described above.
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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 pilot(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 pilot 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 and approved them by adding his signature and date.
Laboratory record notebooks were also reviewed, signed, and dated by the Verification Testing
Leader.
Other data review focused upon the compliance of the chemiluminescent reference and analyzer
data with the quality requirements of Method 7E. The purpose of validating reference Method 7E
data was to ensure usability for the purposes of comparison with the Enerac analyzers. 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, availability of Battelle personnel and
equipment, and other changes or improvements. Any deviation required the approval signature of
Battelle's Verification Testing Leader and the pilot manager. A planned deviation form was used
for documentation and approval of the following changes:
1. Dr. Agnes Kovacs did not participate in the statistical analysis of data from the verification
test.
2. The order of testing was changed, and a span value of 70 percent of range (rather than
100 percent) was used in the pressure sensitivity test.
3. The order of the ambient temperature test was changed.
4. The exact concentrations used in the mixture of S02 and NO for the interference test were
changed.
5. A different diesel generator was used than that originally planned.
6. An oxygen sensor was not used during source tests.
7. Thermo Environmental Models 14A/10 NO/NOx analyzers were used for reference method.
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8. Triplicate calibration points were not run on reference method analyzers.
9. Unheated sample line and tubing were used, based on Battelle's previous experience in
sampling the combustion sources used in this test and other similar sources.
Table 4-1. Results of QC Procedures for Reference NOx Analyzers for Testing of Enerac 3000E
Analyzers
N02 conversion
efficiency
N02 conversion
efficiency
Calibration of reference
method using four points (r2 = 0.9998)
at 0, 30, 60, 100% for
NO
Calibration of reference Meets criteria
method using four points (r2 = 0.9998)
at 0, 30, 60, 100% for
N02
85.5% for Model 14A in 100
ppm and 1,000 ppm ranges
89.9% for Model 10 in 100 ppm
and 1,000 ppm ranges
Meets criteria
Calibrations
(100 ppm range)
Meet ± 2% requirement (relative
to span)
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
< ± 7% (No interference
response observed)
Model 10
Model 14A
NO
NO
Error, % of % of Scale
Error, % of % of Scale
Span
Span
0.6% 30%
0.2% 30%
0.3% 60%
0.3% 60%
no2
no2
Error, % of % of Scale
Error, % of % of Scale
Span
Span
0.2% 30%
0.6% 30%
0.5% 60%
0.2% 60%
There was one undocumented deviation. Due to a delay in the arrival of the protocol gases used
in the verification test, Battelle was not able to run one instrument through the entire test
sequence prior to verification testing. The impact of this deviation on the final data is described in
the Performance System Audits section of this report.
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Finally, a comment is in order concerning the zero and span check procedure used before and
after sampling of each source in the combustion source tests. Zero and span gases (Table 3-3)
were supplied to the reference analyzers by connection to the fitting at the downstream end of the
stainless steel sampling probe, i.e., the sampling probe itself was not used in the zero and span
check. Enerac staff have pointed out that this procedure could allow a leak to go undetected at
that fitting after the zero and span check has been completed and the probe has been reconnected.
The absence of oxygen measurements, which might disclose a leak, adds to this concern. This
issue is pertinent because of a possible leak of room air into the reference analyzer sampling line
during one portion of the source testing, as described in Section 6.2.1.
4.3 Calibration of Laboratory Equipment
Equipment used in the verification test required calibration before use. Equipment types and
calibration dates are listed in Table 4-2. Documentation for calibration of the following equipment
was required before use in the verification test, and was maintained in the test file.
Table 4-2. Equipment Type and Calibration Date
Calibration Date/
Equipment Type
Temperature Check
Flow Controllers (Gas Dilution System) Environics Series 100
6/11/98
Flow Controllers (Gas Dilution System) Environics Model 2020
12/16/98
Digital Temperature Indicator Model 402A
1/7/99
Dwyer Magnahelic Pressure Gauge
1/11/99
Model R-275 In-line Dry Gas Meter
1/11/99
Doric Trendicator 400A Thermocouple Temperature Sensor
1/18/99
Model DTM-115 Reference Dry Gas Meter
9/22/98
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
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# Certified Master Class Calibration Standard Carbon Monoxide
# Nitrogen Acid Rain CEM Zero
# 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
Internal and external performance system audits were conducted and the results are summarized
in the following sections.
4.5.1 Internal Audits
Three internal 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 percent of all data generated during the verification test. A summary of the results of these
audits is provided below.
4.5.1.1 Techni cal Sy stem s Audit
A technical systems audit is a qualitative onsite audit of the physical setup of the test. The
auditors determine the compliance of testing personnel with the test/QA plan. A self-assessment is
required for each test as outlined in the AMS pilot QMP. The QA/QC Reviewer for the verifi-
cation test conducted the internal technical systems audit on January 18, 1999. Observations and
findings from this audit are listed in Table 4-3.
4.5.1.2 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. One such assessment was conducted by Battelle QA staff on
February 4, 1999. No independent assessments of this type were conducted by EPA staff.
The performance evaluation (PE) samples were NO and N02 calibration gases independent of the
test calibration standards containing certified concentrations of NO andN02. 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 values. Percent difference
was used to quantify the accuracy of the results. The PE sample for NO was an EPA protocol gas
having nearly the same concentration as the NO standard used in verification testing, but
purchased from a different commercial supplier. The PE standard for N02 was a
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Table 4-3. Observations and Findings From the Internal Technical Systems Audit
Observation/Finding
Corrective Action/Impact on Final Data
Method 7E calibration was not completed prior to
verification testing. Analyzers gave unreliable results
during first test, which prompted a calibration on
1/13/99. Full four-point calibration was not
performed until 1/15/99 on the 0-100 range and
1/16/99 on the 0-1000 range for both Models 14A
and 10. All criteria meet stated objectives in Method
7E for the calibration (linearity, calibration error)
performed on the 15th and 16th.
From Pressure Sensitivity Test conducted 1/12/99 an
explanation is needed of correction factor to be
applied to data.
Start and stop time for instruments to equilibrate at
each temperature is not noted on data sheets.
Calibration drift for all data reviewed is less than
± 3% relative to the span except Model 10 span post-
test on 1/14/99 for diesel engine test which = 3.6%.
Data for test should be flagged at minimum.
Data and calculations for calibration drift test not
found on test data sheets. Recommend a better system
be implemented for assessing quality of the
calibration drift for reference analyzers immediately
following collection of test data so decision whether
or not to proceed is clear to all participants.
Zero/span values are documented on diesel engine
test data sheets for all tests except on 01-13-98 post-
test blank with no explanation.
Vendor source testing that was conducted prior to the
first full four-point Method 7E calibration was
repeated at a later date. Thus all vendor testing was
conducted with fully calibrated reference analyzers.
There is no impact on verification data because the
first vendor test was repeated after Method 7E
calibration was implemented.
The 02 sensors of the vendor's analyzers showed the
presence of 02 in the sample gas at a time when only
NO in pure N2 was being provided to the analyzers.
This indicated a leakage of air into the sample
manifold (which was at reduced pressure relative to
the room). The amount of dilution caused by the
leakage of air was calculated from the 02 level
observed, and exactly accounted for an apparently
low NO response from the vendor's analyzers. That
is, the 02 data were used to correct the observed NO
responses to what they would have been with no air
leakage. The leak was corrected, and no impact exists
on the Enerac testing.
Added start and stop time to data sheets as a method
to document equilibration.
All source tests with the Enerac analyzers met the
3% requirement. No impact on final data.
Comparison of drift is easily made visually; written
comments will be added if termination of a test is
called for.
This test was terminated. Notes were added as
suggested and the test was later repeated in its
entirety. No impact on Enerac testing.
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commercial standard of 50.5 ppm N02 in air, whose concentration had been confirmed by
comparison with a 50 ppm Standard Reference Material of NO in nitrogen, obtained from the
National Institute of Standards and Technology. Table 4-4 summarizes the reference method
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. As shown in Table 4-4, all of
the observed concentrations were well within the acceptance ranges.
Table 4-4. Performance Evaluation Results
Reading (V)
Zero (V)
Zero
Corrected
Apparent
Concentration*
Percent
Difference**
Limits
Unit 14A
Test Std
NO in N2
(ppm)
3,925
9.92
0.01
9.91
3905.3
0.5%
±2%
PE Std
3,988
10.13
0.01
10.12
Unit 10
Test Std
NO in N2
(ppm)
3,925
1.01
-0.01
1.03
3895.7
0.7%
±2%
PE Std
3,988
1.04
-0.01
1.05
Unit 14A
Test Std
N02 in
Air (ppm)
50.0***
4.40
0.01
4.39
48.7
2.5%
±5%
PE Std
50.5
4.56
0.02
4.54
Unit 10
Test Std
N02 in
Air (ppm)
50.0***
0.44
-0.01
0.45
50.0
0.1%
±5%
PE Std
50.5
0.44
-0.01
0.45
Concentration of Test Standard indicated by comparison to the Performance Evaluation Standard
**Percent difference of apparent concentration relative to Test Standard concentration.
***Prepared by dilution of 493.2 ppm N02 protocol gas.
4.5.1.3 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 percent 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.
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The QA/QC Reviewer for the verification test audited 10 percent of the raw data. Test data sheets
and laboratory record books were reviewed, and calculations and other algorithms were verified.
Calibration drift test results were calculated and compared to the Method 7E criteria. Calculations
that were used to assess the four-point calibration of the reference method were also verified to be
correct.
4.5.2 External Audit
EPA conducted an on-site technical systems audit during the verification testing. This audit was
conducted to observe and evaluate whether the verification team followed the test/QA plan. The
external technical systems audit report is attached in Appendix B and the assessment is
summarized below.
The auditors assessed the verification test procedures and personnel against the Quality Manage-
ment Plan for the ETV Advanced Monitoring Systems Pilot,(7) the Test/QA Plan for Verification
of Portable NO/NO 2 Emission Analyzers,(1) and U.S. EPA Method 7E Determination of Nitrogen
Oxides Emissions from Stationary Sources (Instrumental Analyzer Procedure) {2) The auditors
were on site from January 20, 1999, through January 21, 1999. The technical systems audit was
performed on the flow rate and ambient temperature laboratory tests and the relative accuracy
tests with the gas rangetop, water heater, and a portion of the high RPM emissions of the diesel
generator. No performance evaluations were conducted as a part of this audit.
This external technical systems audit showed that the verification test was well managed,
particularly considering its complexity. All personnel appeared to be well trained for their
particular duties. All involved showed enthusiasm and ingenuity during the verification testing.
Personnel were very familiar with the test/QA plan. With one exception, differences for this
verification test from the original test/QA plan were well documented by deviation reports on file
at Battelle. The deviation report format includes a date, cites the deviation, provides an explana-
tion of the deviation, and requires a Battelle approval signature. It was impressive that the
deviation reports were present and were completed up front.
Two major findings resulted from this external technical systems audit. First, as a result of a delay
in the arrival of the protocol gases used in the verification test, Battelle was not able to run one of
the instruments through the test sequence prior to the first test. This undocumented deviation was
from Section 5.6 of the test/QA plan, Test Schedule, and stated "To avoid bias in testing of the
first analyzers through the sequence, Battelle's personnel will first conduct the entire test
sequence using an analyzer already on hand at Battelle. Testing will then continue with analyzers
named in Section 2.4." Second, the test/QA plan states that "The chemiluminescent monitors to
be used for Method 7E reference measurements will be subjected to a four-point calibration with
NO prior to the start of verification testing, on each measurement range to be used for
verification." The combustion source tests were started on January 13, 1999. No four-point
calibration with NO was recorded in the combustion source testing laboratory notebook prior to
January 13. This finding is also a finding in Battelle's internal audit conducted during the first
week of the verification test.
22
-------
The impact of these two findings on the data presented in this report is as follows. Although
Battelle did not run an instrument through the entire test sequence prior to initiating testing, each
component of the test system was checked independently. Therefore, the absence of this pre-test
check will not impact the final data. The lack of initial calibration of the reference analyzers does
not affect the verification data since the calibration was completed before any combustion source
testing used for verification.
23
-------
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 Enerac analyzer. The calibration model used was
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 (oc) of the measured concentration values (c) was modeled by the following
relationship,
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.
Yc = h(c) + error
(1)
o2c =a +
(2)
weight = w c =
(3)
24
-------
The form of the linear regression model fitted was h(c) ao 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 \Yc) = (4)
a j
A test for departure from linearity was carried out by comparing the residual mean square
1 6 ~~
t£ (YC ~ ao - aiC)\Wc. (5)
4 ,-=i ' ' '
to an F-distribution with 6-2 = 4 numerator degrees of freedom.
Yci is the average of the nci analyzer responses at the ith calibration concentration, cr 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.
E E
t=i j=i
(Xc
a.J
-a,
~aic)2
w . =
E E
j=i
(Y - Y )2 w + (7 -a„ -a,c)
^ CI CI' CI Z—/ V CIJ 0 1 I'
nw
CI CI
i = l
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
LOD =
(a + 3o ) - a
^ O O' G
a,
3a
a,
(6)
where a0 is the estimated standard deviation at zero concentration. The LOD is estimated as
LOD = 3a0 / a0. The standard error of the estimated detection limit is approximately
25
-------
SE (LOD) a LOD —-—
\ 2(«-l)
+
a
\
/
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 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 percent of that change was achieved. Using data taken
every 10 seconds, the following calculation was carried out:
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:
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:
where time950/o is the time at which ResponseRX occurred and Time; 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
Total Response = Rc - Rz
Response950/o = 0.95(Total Response) + Rz.
RT = Time950/o - Time,,
26
-------
the actual concentration of the interferant. For example, an analyzer that measures NO is
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 percent. 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 = ft/ (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:
_ v
I JI ^ d
\d\ + fn-1
Jn (7)
RA = = s— x 100% v 7
x
where d refers to the difference between the average of the two reference units and one of the
tested units and x corresponds to the average of the two reference unit values. Sd denotes the
sample standard deviation of the differences, based on n = 9 samples, while tan_i 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 percent confidence level, one-tailed). The RA
calculated in this way can be determined as an upper confidence bound for the relative bias of the
analyzer
values.
d
jx , where the bar indicates the average value of the differences or of the reference
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 *
S„
\fnx ^
0.3634 + t
n-1
2(«-l)
X 100%
(8)
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 calculation
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
28
-------
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 perfor-
mance 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 units of each
analyzer were compared using statistical tests of difference. For example, the slopes of the cali-
bration 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 possible data points.
29
-------
Chapter 6
Statistical Results
6.1 Laboratory Tests
6.1.1 Linearity
Tables 6-la through d list the data obtained in the linearity tests for NO and N02. The response of
both the NO and N02 sensors in each analyzer is shown in Tables 6-la through d. Table 6-la
shows the data obtained in the NO test over 0 to 1,000 ppm, and Table 6-lb shows the data from
the N02 test over a 0 to 400 ppm range. Tables 6-lc and d list the data obtained in additional NO
linearity tests over ranges of 0 to 3,000 ppm and 0 to 300 ppm, respectively. As noted in Section
3.2.1, the Enerac analyzers reported 0 ppm at all NO concentrations below 3 ppm, in the 0 to
1,000 ppm and 0 to 3,000 ppm NO tests (Tables 6-la and c, respectively) because of the NO
control modules used in the analyzers.
Tables 6-2a through c show the results of the linear calibration curve fits for each unit and each
analyte, based on the data shown in Tables 6-la through d. Tables 6-2a through c show that the
linearity tests of the Enerac analyzers gave regression slopes for NO that range from 0.986 to
1.009, and for N02 that are both 0.992. These slopes are all in the range of 0.98 to 1.02, stated as
acceptable in the SCAQMD tests protocol.(8) The R2 values for NO range from 0.9997 to 0.9999,
while the values for N02 are 0.9987 and 0.9980. These all exceed or are close to the value of
0.999 stated as acceptable in the SCAQMD protocol.(8)
The linearity test data in Tables 6-la through b also indicate the extent of cross-sensitivity of the
Enerac NO and N02 sensors. In NO tests to 1,000 ppm (Table 6-la) and 300 ppm (Table 6-ld),
no response to NO was seen on the N02 sensors of the Enerac analyzers. However, some
response was seen in the linearity test to 3,000 ppm NO (Table 6-lc). Using those data, linear
regression of the N02 responses of the analyzers against the NO levels provided (Table 6-lc)
gives the following regression equations:
Unit A N02 Response = 0.00216 (Actual NO) -0.98 ppm
Unit B N02 Response = 0.00251 (Actual NO) -1.01 ppm
30
-------
Table 6-la. Data from NO Linearity Test Over 0-1,000 ppm Range on Enerac 3000E
Analyzers
Actual NO
Unit A NO
Unit A N02
Unit B NO
Unit B N02
Reading
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
1
0
0
0
0
0
2
1002
994
0
997
0
3
99.7
104
0
103
0
4
400.7
413
0
413
0
5
0
0
0
0
0
6
701.2
711
0
711
0
7
200.2
208
0
207
0
8
99.7
104
0
104
0
9
0
0
0
0
0
10
200.2
207
0
208
0
11
400.7
413
0
414
0
12
701.2
716
0
716
0
13
0
0
0
3
0
14
1002
995
0
1000
0
15
701.2
713
0
716
0
16
400.7
414
0
417
0
17
0
0
0
3
0
18
200.2
207
0
207
0
19
99.7
104
0
105
0
20
1002
994
0
999
0
21
0
0
0
3
0
31
-------
Table 6-lb. Data from N02 Linearity Test Over 0-400 ppm Range on Enerac 3000E
Analyzers
Actual N02
Unit A NO
Unit A N02
Unit B NO
Unit B N02
Number
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
1
0
0
0
0
0
2
400.9
0
403
0
404
3
48.2
1
47
1
46
4
197
0
195
0
194
5
0
1
3
1
3
6
345.7
0
342
0
342
7
97.2
0
97
0
95
8
48.2
0
45
0
44
9
0
1
0
1
0
10
97.2
0
93
0
90
11
197
0
195
0
193
12
345.7
0
348
0
349
13
0
1
4
1
4
14
400.9
0
403
0
406
15
345.7
0
352
0
354
16
197
0
202
0
201
17
0
1
4
1
4
18
97.2
0
95
0
92
19
48.2
0
45
1
43
20
400.9
0
404
0
406
21
0
1
4
1
4
32
-------
Table 6-lc. Data from NO Linearity Test Over 0-3,000 ppm Range on Enerac 3000E
Analyzers
Actual NO
Unit A NO
Unit A N02
Unit B NO
Unit B N02
Number
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
1
0
15
0
18
0
2
3005
3020
12
2985
12
3
292.7
287
0
283
0
4
1198
1219
0
1194
0
5
0
17
0
19
0
6
2103
2114
0
2112
3
7
592.6
591
0
586
0
8
292.7
276
0
271
0
9
0
11
0
19
0
10
592.6
585
0
586
0
11
1198
1213
0
1194
0
12
2103
2119
0
2095
0
13
0
19
0
19
0
14
3005
2985
8
2991
8
15
2103
2129
0
2095
3
16
1198
1219
0
1208
0
17
0
17
0
19
0
18
592.6
585
0
586
0
19
292.7
276
0
276
0
20
3005
2994
6
2981
7
21
0
17
0
19
0
33
-------
Table 6-ld. Data from NO Linearity Test Over 0-300 ppm Range on Enerac 3000E
Analyzers
Number
Actual NO Unit A NO
(ppm) (ppm)
Unit A N02
(ppm)
Unit B NO
(ppm)
Unit B N02
(ppm)
1
0
1
0
1
0
2
300.5
299
0
300
0
3
29.7
32
0
32
0
4
120
124
0
124
0
5
0
1
0
1
0
6
209.9
214
0
213
0
7
59.8
63
0
63
0
8
29.7
31
0
32
0
9
0
1
0
1
0
10
59.8
62
0
63
0
11
120
125
0
124
0
12
210.3
214
0
215
0
13
0
1
0
1
0
14
300.5
301
0
302
0
15
210.3
215
0
215
0
16
120
125
0
125
0
17
0
1
0
1
0
18
59.8
63
0
63
0
19
29.7
32
0
32
0
20
300.5
302
0
302
0
21
0
1
0
1
0
Table 6-2a. Statistical Results for First Test of Linearity (NO span = 1000
N02 span = 400 ppm)
ppm,
Unit A
Unit B
Linear Regression
NO
no2
NO
no2
Intercept (ppm)
Err)
Slope (Std Err)
R2
(Std
7.284 (2.093)
0.996 (0.005)
0.9997
0.686 (0.844)
0.992 (0.008)
0.9987
3.545 (1.264)
1.009 (0.004)
0.9997
0.204 (1.026)
0.992 (0.010)
0.9980
34
-------
Table 6-2b. Statistical Results for Second Test of Linearity (NO span = 3000 ppm)
Unit A
Unit B
Linear Regression
NO
NO
Intercept (ppm) (Std Err)
10.043 (3.237)
18.759 (0.383)
Slope (Std Err)
0.996 (0.004)
0.986 (0.002)
R2
0.9997
0.9999
Table 6-2c. Statistical Results for Third Test of Linearity (NO span =
300 ppm)
Unit A
Unit B
Linear Regression
NO
NO
Intercept (ppm) (Std Err)
2.820 (0.599)
2.392 (0.269)
Slope (Std Err)
0.999 (0.005)
1.005 (0.004)
R2
0.9997
0.9998
with R2 values of 0.52 and 0.67, respectively. These results indicate a slight sensitivity of the N02
sensors to NO, amounting to about 0.2 percent of the actual NO level. This degree of cross-
sensitivity is negligible in any real-world application.
As seen in Table 6-lb, no response was observed from the Enerac NO sensors when sampling up
to 400 ppm of N02, indicating no cross-sensitivity of the NO sensors to N02.
6.1.2 Detection Limit
Table 6-3 shows the estimated detection limits for each test unit and each analyte, calculated from
the data obtained in each linearity test.
Table 6-3 displays the estimated detection limits, and their standard errors for NO and N02,
separately for each Enerac analyzer. The determination of NO detection limits from the 1,000
ppm and 3,000 ppm NO linearity tests may have been affected by the operating mode used in
those tests, in which the Enerac analyzers read zero at all NO concentrations below 3 ppm. In
addition, in other tests the analyzers gave identically the same 1 ppm response on all zero gas
samples. As a result, in some tests all readings on zero gas were the same, and there was no
variation in zero readings with which to estimate the detection limit. The detection limit for NO
on Unit A was 8.3 ppm in the 0 to 3,000 ppm test; detection limits for NO on Unit B were 4.9
ppm in the 0 to 1,000 ppm test and 1.2 ppm in the 0 to 3,000 ppm test. Detection limits for N02
were about 6 ppm in the 0 to 400 ppm test on both analyzers. Both NO units showed a constant
1 ppm response on zero air in the 0 to 300 ppm test (Table 6-Id), indicating excellent stability and
suggesting a detection limit less than the 1 ppm measurement resolution.
35
-------
Table 6-3. Estimated Detection Limits for Enerac 3000E Analyzers
Unit A Unit B
NO
no2
NO
no2
Estimated Detection Limit (ppm)*
o****
5.973
4.886
5.972
(Standard Error) (ppm)
(0.000)
(1.890)
(1.545)
(1.889)
Estimated Detection Limit (ppm)**
8.300
—
1.242
—
(Standard Error) (ppm)
(2.625)
(0.393)
Estimated Detection Limit (ppm)***
o****
—
o****
—
(Standard Error) (ppm)
(0.000)
(0.000)
*First test, Tables 6-la and b.
**Second test, Table 6-lc.
***Third test, Table 6-ld.
****No variation in zero responses with which to assess detection limit.
6.1.3 Response Time
Table 6-4 lists the data obtained in the response time test of the Enerac 3000E 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.
Table 6-5 shows that the Enerac 3000E analyzers provide substantially faster responses for NO
than for N02, and that the two analyzers were very similar in their response to both species. Time
response for NO was about 60 seconds, and for N02 was about 100 seconds. These response
times are well within the 4-minute time response criterion generally required of portable N0/N02
analyzers.(8)
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 concen-
trations of 1,000 ppm NO and 400 ppm N02 were used for this test. Greater zero and span
differences were seen for N02 than for NO on both analyzers. NO zero readings (Table 6-6) were
all zero, and consequently so were the zero differences (Table 6-7). This lack of zero variation
may be real, or the operating mode of the Enerac analyzers, which forced readings of 0 ppm at all
NO levels below 3 ppm, may have affected the results. NO span differences were -4 to 2 ppm,
equivalent to 0.4 percent or less of the 1,000 ppm span level. N02 zero drift was 4 ppm down-
ward on both analyzers during the overnight shutdown. Span differences for N02 were equivalent
to 2.5 to 2.8 percent of the 400 ppm span level.
36
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Table 6-4. Response Time Data for Enerac 3000E Analyzers
Unit A NO
Unit A N02
Unit B NO
Unit B N02
Time (sec)
(ppm)
(ppm)
(ppm)
(ppm)
0
0
0
0
0
10
75
0
40
0
20
310
34
239
36
30
523
117
481
117
40
603
189
584
192
50
651
239
641
240
60
677
275
673
275
70
693
297
690
296
80
702
311
698
310
90
708
320
703
319
100
708
326
706
324
110
707
329
708
328
120
708
332
707
330
130
709
334
711
332
140
711
336
711
334
150
713
337
713
336
160
713
338
713
337
170
713
339
711
338
180
711
340
711
339
190
340
340
200
341
340
210
341
341
220
342
342
Table 6-5. Response Time Results for Enerac 3000E Analyzers
Unit A
Unit B
NO
no2
NO
no2
Response Time (sec)*
59
98
61
102
* The analyzer's responses were recorded at 10-second intervals; therefore the point in time when the
95 percent response was achieved was determined by interpolating between recorded times to the nearest
second.
37
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Table 6-6. Data from Interrupted Sampling Test with Enerac 3000E Analyzers
Unit A NO
Unit A N02
Unit B NO
Unit B N02
Pre-Shutdown Date:
1/25/99
Time:
22:30
Pre-Shutdown Zero (ppm):
0
4
0
4
Pre-Shutdown Span (ppm):
1000
404
1000
406
Post-Shutdown Date:
1/26/99
Time:
10:00
Post-Shutdown Zero (ppm):
0
0
0
0
Post-Shutdown Span (ppm):
998
394
1004
395
Table 6-7. Pre- to Post-Test Differences as a Result of Interruption of Operation of Enerac
3000E Analyzers
Unit A
Unit B
Pre-Shutdown—Post-Shutdown
NO
no2
NO
no2
Zero Difference (ppm)
0
4
0
4
Span Difference (ppm)
2
10
-4
11
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. Note that cross-sensitivity
to NO and N02 has been addressed using the linearity data, in Section 6.1.1.
Table 6-9 indicates that none of the individual interferants produced a response from the NO or
N02 sensors of the Enerac analyzers (i.e., both analyzers read 0 ppm throughout the sampling of
those interferants). Even assuming that a 2 ppm response to one of the interferants was hidden
(forced to zero) by the analyzers' operating mode for NO, the maximum relative sensitivity to any
of the individual interferants would be less than 0.5 percent. The last row of entries in Table 6-9
indicates that, for the one mixed interferant, S02 + NO, the response to NO was higher for both
Units A and B than the 385 ppm NO supplied. If the higher NO response is ascribed to a positive
interference from the S02 present along with the NO, then the relative sensitivity to S02 is
effectively 8 to 9 percent [e.g., (426-385)7451 x 100 = 9.1%].
38
-------
Table 6-8. Data from Interference Tests on Enerac 3000E Analyzers
Interferant Interferant, Cone.
Response (ppm equivalent)
Gas (ppm)
Unit i
\ NO
Unit A N02
Unit B NO
Unit B N02
Zero
0
0
0
0
CO 496 ppm
0
0
0
0
Zero
0
0
0
0
C02 5.03%
0
0
0
0
Zero
0
0
0
0
NH3 494 ppm
0
0
0
0
Zero
0
0
0
0
HCs 590 ppm
0
0
0
0
Zero
0
0
0
0
S02 501 ppm
0
0
0
0
Zero
0
0
0
0
SO, + NO 451+385 ppm
426
0
422
0
Table 6-9. Results of Interference
Tests of Enerac 3000E Analyzers
Unit A
Response ppm
Unit B Response ppm
(relative sensitivity, %)
(relative sensitivity, %)
Interferent
NO
no2
NO
no2
CO (496 ppm)
0
0
0
0
C02 (5.03 %)
0
0
0
0
NH3 (494 ppm)
0
0
0
0
HCs (590 ppm)
0
0
0
0
S02 (501 ppm)
0
0
0
0
S02 (451 ppm) +
41
0
37
0
NO (385ppm)
(9.1%)
(8.2%)
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 pres-
sures. Table 6-11 also indicates whether zero and span differences are statistically significant at
the 95 percent confidence level. No pressure effect on zero readings was seen with either analyzer
for NO or N02. A significant pressure effect was seen on N02 span readings, but the results are
due almost entirely to an elevation of the span readings at increased pressure. At reduced
pressure, N02 span readings were essentially identical to those at ambient pressure. The 28 ppm
39
-------
increase in N02 span response at increased pressure is equivalent to 8.1 percent of the 345 ppm
N02 span concentration used. This much larger difference in span response at increased pressure
may be related to the much larger effect of increased pressure on analyzer flow rates, which is
described below.
The pressure effect on NO span values was smaller and less consistent than that for N02. The
span differences shown in Table 6-11 are equivalent to 0.6 to 1.7 percent of the 700 ppm NO
span concentration used.
Tables 6-10 and 6-11 also indicate a surprisingly large dependence of the sample gas flow rate
drawn by the two analyzers on the duct pressure. Sample flow rates at +10 inches of water
exceeded those at ambient pressure by 99 to 163 percent; flow rates at -10 inches of water were
reduced by 20 to 22 percent. The reason for this finding is unclear, but may relate to the internal
plumbing of the Enerac analyzers; as noted above, these large differences in flow rates were
associated with small differences in zero or span response.
6.1.7 Ambient Temperature
Table 6-12 lists the data obtained in the ambient temperature test with the Enerac 3000E
analyzers.
Table 6-13 summarizes the sensitivity of the analyzers to changes in ambient temperature. This
table is based on the data shown in Table 6-12, where the span values are 700 ppm for NO and
345 ppm for N02.
Table 6-13 indicates whether zero and span differences are statistically significant with tempera-
ture at the 95 percent confidence level. No dependence of N02 zero readings on temperature was
found; however, a small but statistically significant dependence of NO zero readings was found,
with the highest readings at elevated temperature. As with all assessments of NO zero readings on
the Enerac analyzers, it is not clear whether the NO operating mode of the analyzers has obscured
or exaggerated real variability by forcing readings below 3 ppm to zero. In any case, in light of the
known potential for electrochemical NO sensors to drift with temperature, the small NO zero
drifts observed (i.e., about 5 ppm or less, Table 6-13) must be considered of minimal practical
importance.
A significant dependence of span values on ambient temperature was found for NO with both
analyzers and for N02 with Unit A (Table 6-13). However, even the NO results present an
inconsistent picture (see Table 6-12). For both units at elevated temperature, the NO span value
was lower than that at room temperature, but by different amounts. At reduced temperature, for
Unit A, the NO span value was almost the same as that at room temperature; whereas for Unit B
the NO span value was greater than that at room temperature. These results suggest a reduction
in NO span response as temperature increases, but do not accurately quantify that dependence.
The Unit A N02 results suggest the opposite effect (i.e., an increase in response as temperature
increases), but the Unit B results do not strongly support that trend. It must be noted that the first
room temperature test and the elevated temperature test were done in the evening, and the
40
-------
Table 6-10. Data from Pressure Sensitivity Test for Enerac 3000E Analyzers
Pressure Unit A NO Unit A N02 Unit B NO Unit B N02
Ambient Flow rate (ccm)
667
667
663
663
Zero (ppm)
0
0
0
0
NO span (ppm)
721
0
721
0
Zero (ppm)
0
0
0
0
N02 span (ppm)
7
342
0
336
Zero (ppm)
0
0
0
0
+10 in. H20 Flow rate (ccm)
1755
1755
1318
1318
Zero (ppm)
0
0
0
0
NO span (ppm)
725
0
711
0
Zero (ppm)
0
0
0
0
N02 span (ppm)
6
370
0
364
Zero (ppm)
0
0
0
0
-10 in. H20 Flow rate (ccm)
518
518
528
528
Zero (ppm)
0
0
0
0
NO span (ppm)
709
0
710
0
Zero (ppm)
0
0
3
0
N02 span (ppm)
7
342
0
337
Zero (ppm)
0
0
0
0
Table 6-11. Pressure Sensitivity Results for Enerac 3000E Analyzers
Unit A
Unit B
NO
no2
NO NO,
Zero High-Ambient (ppm cliff*)
0
0
0
0
Low-Ambient (ppm diff)
0
0
1
0
Significant Pressure Effect
N
N
N
N
Span High-Ambient (ppm diff)
4
28
-10
28
Low-Ambient (ppm diff)
-12
0
-11
1
Significant Pressure Effect
Y
Y
Y
Y
Flow High-Ambient (ccm diff*)
1088
655
Rate Low-Ambient (ccm diff)
-149
-135
* ppm or ccm difference between high/low and ambient pressures. The differences were calculated based on
the average of the zero values.
41
-------
Table 6-12. Data from Ambient Temperature Test of Enerac 3000E Analyzers
Unit A NO Unit A N02 Unit B NO Unit B NO,
Condition (PPm) (PPm) (PPm) (PPm)
(Room Temp.)
Temp. 24.4°C (76°F)
Zero 0 0 0 0
NO span 718 7 719 7
Zero 0 0 0 0
N02 span 7 349 0 346
(Heated)
Temp. 41.7°C (107°F)
Zero 3 0 3 0
NO span 709 5 717 4
Zero 6 0 8 0
N02 span 13 352 4 338
(Cooled)
Temp. 10°C (50°F)
Zero 0 0 0 0
NO span 733 4 740 3
Zero 0 0 0 0
N02 span 5 326 0 330
(Room Temp.)
Temp. 24.4°C (76°F)
Zero 0 0 0 0
NO span 734 7 721 6
Zero 0 0 0 0
N02 span 6 336 0 333
42
-------
Table 6-13. Ambient Temperature Effects on Enerac 3000E Analyzers
NO
Unit A
no2
Unit B
NO
no2
Zero*
Heat-Room (ppm diff*)
4.5
0
5.5
0
Cool-Room (ppm diff)
0
0
0
0
Significant Temp Effect**
Y
N
Y
N
Span
Heat-Room (ppm diff)
-17
9.5
-3
-1.5
Cool-Room (ppm diff)
7
-16.5
20
-9.5
Significant Temp. Effect
Y
Y
Y
N
* ppm difference between heated/cooled and room temperatures. The differences were calculated from the
average of the recorded responses at room temperature.
second room temperature and reduced temperature tests were done the following morning. Thus,
day-to-day drift may also contribute to the changes in zero and span readings that are attributed
to temperature effects. Overall, the NO span differences amount to 2.9 percent or less of the
700 ppm NO span level, and those for N02 amount to 4.8 percent or less of the 345 ppm N02
span level. No consistent temperature dependence can be inferred from these results.
6.1.8 Zero and 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.
The results in Table 6-15 for the first linearity test show no zero drift for NO, but 4 ppm drift for
N02. However, the NO zero drift may have been as large as ±2 ppm, and would still be read as
zero because of the operating mode of the analyzers. Span drifts for NO and N02 equate to
0.1 percent, and up to 1.75 percent, of the respective span concentrations.
In the second linearity test (with up to 3,000 ppm NO), NO zero drift was 7 and 12 ppm on the
two units, respectively. Span drift differed widely on the two units, but even for Unit A, the span
drift was only 1.5 percent of the 3,000 ppm span concentration. The third linearity test (up to
300 ppm NO) showed that both zero and span drift of the NO sensors was within 1 ppm, or
0.3 percent of the span concentration.
The ambient temperature test showed no zero drift for either NO or N02 on either analyzer. That
for NO could have been as large as ±2 ppm, because of the operating mode of the analyzers. The
N02 span drift of 13 ppm found for both analyzers amounts to 3.8 percent of the N02 span con-
centration. The NO span drift values differed considerably between the two units (Table 6-15).
The larger value, 16 ppm drift on Unit A, amounts to 2.3 percent of the NO span concentration.
43
-------
Table 6-14. Data from Linearity and Ambient Temperature Tests Used to Assess Zero and
Span Drift of the Enerac 3000E Analyzers.
Unit A NO
Unit A N02
Unit B NO
Unit B N02
Test
(ppm)
(ppm)
(ppm)
(ppm)
First Linearity Test*
Pre-Test Zero*
0
0
0
0
Pre-Test Span*
999
399
1001
399
Post-Test Zero*
0
4
0
4
Post-Test Span*
1000
404
1000
406
Second Linearity Test**
Pre-Test Zero**
5
-
12
-
Pre-Test Span**
3039
-
2980
-
Post-Test Zero**
17
-
19
-
Post-Test Span**
2994
-
2981
-
Third Linearity Test***
Pre-Test Zero***
0
-
0
-
Pre-Test Span***
301
-
301
-
Post-Test Zero***
1
-
1
-
Post-Test Span***
302
-
302
-
Ambient Temperature
Pre-Test Zero
0
0
0
0
Pre-Test Span
718
349
719
346
Post-Test Zero
0
0
0
0
Post-Test Soari
734
336
721
333
*NO 0 - 1,000 ppm and N02 0 - 400 ppm.
**NO 0 - 3,000 ppm.
***NO 0 - 300 ppm.
Table 6-15. Zero and Span Drift Results for the Enerac 3000E Analyzers
Unit A
Unit B
NO
no2
NO
no2
Pre- and Post-Differences
(ppm)
(ppm)
(ppm)
(ppm)
First Linearity Test
Zero
0
-4
0
-4
Span
-1
-5
1
-7
Second Linearity Test
Zero
-12
-
-7
-
Span
45
-
-1
-
Third Linearity Test
Zero
-1
-
-1
-
Span
-1
-
-1
-
Ambient Temperature Test
Zero*
0
0
0
0
Span
-16
13
-2
13
* Drift is the difference (pre-monitoring minus post-monitoring) between the first and last zero check
response averages at room temperature.
44
-------
Note that these span drift values were obtained over the course of two days, i.e., the two room
temperature span checks were conducted on one evening and on the following morning,
respectively (Section 6.1.7). Even so, nearly all the Enerac zero and span drift results meet the
3 percent requirements stated in the SCAQMD test protocol.(8)
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 of the four
combustion sources. Note that the Enerac analyzers measure NO and N02, and the indicated NOx
totals are the sum of those data; in contrast, the reference monitors measure NO and NOx, and
N02 is determined by difference. Tables 6-16a through d show that a wide range of NO and N02
concentrations was emitted by the four sources. However, it should be noted that, even so, the
NO and N02 emission levels covered only a small part of the measurement range of the Enerac
3000E analyzers.
Table 6-17 displays the relative accuracy (in percent) for NO, N02, and NOx of Enerac 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.
The relative accuracy results of the Enerac analyzers varied with different sources. With the gas
rangetop (Table 6-16a), the NO responses of the Enerac units were generally within about 1 ppm
of the reference analyzers (i.e., within the measurement resolution of the analyzers), resulting in
relative accuracies of 16 and 27 percent for Units A and B at the low NO levels observed. On the
other hand, both Enerac units indicated zero for N02 throughout the test, resulting in relative
accuracies over 100 percent at the 2 ppm N02 levels observed. Note that this behavior is not due
to an operating mode of the analyzer as described in Sections 3.2.1 and 6.1.1; that mode applies
to NO measurements rather than to N02. As a consequence of the failure to detect N02, the NOx
totals from the Enerac analyzers with the gas rangetop were consistently low by 1 to 2 ppm,
resulting in relative accuracies for NOx of about 20 percent on both analyzers (Table 6-17).
With the gas water heater (Table 6-16b), similar performance was observed. In this case the
Enerac units provided good relative accuracy for NO: 9 percent and 3.4 percent for Units A and
B, respectively. However, no response was seen for N02 at levels of 4 to 6 ppm. Overall, NOx
relative accuracy with the water heater was about 16 percent and 11 percent, respectively, despite
the failure to detect N02. This result is a consequence of the high proportion of NO to N02 in the
water heater emissions.
The performance of the Enerac analyzers differed greatly between the diesel test at high RPM
(Table 6-16c) and that at idle (Table 6-16d). In the high RPM test, both Enerac analyzers gave
NO readings considerably higher than those of the reference analyzers, and N02 readings con-
siderably lower (Table 6-16c). As a result, relative accuracy for both NO and N02 is poor for
45
-------
Table 6-16a. Data from the Gas Rangetop in Verification Testing of Enerac 3000E Analyzers
Enerac Analyzer Data
Reference Analyzer Data
Unit A NO
Unit A N02
Unit A NOs
Unit B NO
Unit B N02
Unit B NOx
14ANO
14A N02
14A NOs
10 NO
10 no2
10 NOx
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
1
5
0
5
5
0
5
4.4
2.3
6.7
4.9
1.9
6.8
2
6
0
6
6
0
6
4.8
2.2
6.9
5.2
1.8
7.0
3
6
0
6
6
0
6
4.9
2.4
7.3
5.4
2.2
7.6
4
6
0
6
6
0
6
5.0
2.2
7.2
5.4
2.3
7.7
5
6
0
6
6
0
6
5.2
2.1
7.3
5.7
2.1
7.8
6
6
0
6
6
0
6
5.2
2.0
7.2
5.6
2.2
7.8
7
6
0
6
7
0
7
5.2
2.0
7.2
5.6
2.2
7.8
8
6
0
6
7
0
7
5.1
2.2
7.3
5.6
2.3
7.9
9
6
0
6
7
0
7
4.9
2.5
7.4
5.6
2.4
8.0
On
Table 6-16b. Data from Gas Water Heater in Verification Testing of Enerac 3000E Analyzers
Enerac Analyzer Data
Reference Analyzer Data
Unit A NO
Unit A N02
Unit A NOs
Unit B NO
Unit B N02
Unit B NOx
14ANO
14A NO,
14A NOs
10 NO
10 no2
10 NOx
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
1
76
0
76
80
0
80
79.1
3.7
82.8
84.9
5.2
90.0
2
62
0
62
66
0
66
65.4
5.5
70.8
69.2
5.3
74.6
3
64
0
64
68
0
68
62.3
5.8
68.1
68.6
1.4
70.0
4
53
0
53
57
0
57
55.7
5.0
60.7
59.0
5.5
64.5
5
53
0
53
56
0
56
54.8
5.9
60.7
58.8
5.9
64.7
6
50
0
50
54
0
54
53.6
4.1
57.7
56.7
5.1
61.8
7
50
0
50
53
0
53
52.8
5.0
57.8
56.7
5.1
61.8
8
50
0
50
53
0
53
52.6
5.0
57.6
56.4
5.1
61.6
9
50
0
50
53
0
53
53.1
4.7
57.8
57.2
4.9
62.1
-------
Table 6-16c. Data from the Diesel Generator at High RPM in Verification Testing of Enerac 3000E Analyzers
Unit A NO
(ppm)
Unit A N02
(ppm)
Enerac Analyzer Data
Unit A NOs Unit B NO
(ppm) (ppm)
Unit B N02
(ppm)
Unit B NOx
(ppm)
14ANO
(ppm)
14A NO,
(ppm)
Reference Analyzer Data
14A NOs 10 NO
(ppm) (ppm)
10 no2
(ppm)
10 NOx
(ppm)
1
169
12
181
170
15
185
108.3
54.1
162.4
108.1
49.0
157.1
2
152
17
169
159
13
172
97.4
58.5
155.9
96.9
55.2
152.2
3
146
13
159
164
7
171
96.4
53.7
150.1
96.9
51.1
148.0
4
155
11
166
167
5
172
96.5
54.4
150.9
96.9
51.1
148.0
5
156
12
168
166
6
172
96.2
55.0
151.3
96.9
51.1
148.0
6
156
12
168
166
6
172
94.3
55.1
149.4
95.1
52.1
147.2
7
154
12
166
163
6
169
91.0
56.4
147.4
92.3
52.1
144.4
8
152
13
165
162
7
169
90.4
56.3
146.7
91.3
52.1
143.5
9
152
12
164
162
6
168
88.8
55.9
144.7
90.4
51.1
141.5
Table 6-
¦16d. Data from Diesel Generator at Idle in Verification Testin
g of Enerac 3000E Analyzers
Unit A NO
(ppm)
Unit A N02
(ppm)
Enerac Analyzer Data
Unit A NOs Unit B NO
(ppm) (ppm)
Unit B N02
(ppm)
Unit B NOx
(ppm)
14ANO
(ppm)
14A NO,
(ppm)
Reference Analyzer Data
14A NOs 10 NO
(ppm) (ppm)
10 no2
(ppm)
10 NOx
(ppm)
i
338
138
476
343
129
472
271.6
109.1
380.6
272.1
98.2
370.3
2
336
137
473
343
130
473
281.7
111.1
392.8
277.7
103.4
381.1
3
336
138
474
343
132
475
281.6
117.3
398.9
278.7
107.5
386.2
4
336
140
476
343
132
475
283.8
119.3
403.0
279.6
109.6
389.2
5
333
140
473
341
132
473
280.9
122.3
403.3
277.7
109.6
387.4
6
335
141
476
343
136
479
285.5
120.5
406.1
280.5
110.7
391.2
7
337
141
478
346
137
483
284.1
123.3
407.4
279.6
112.7
392.3
8
334
142
476
344
139
483
284.7
126.0
410.7
278.7
113.8
392.4
9
326
146
472
335
145
480
285.5
122.7
408.3
278.7
112.7
391.4
-------
both analyzers in this test (Table 6-17). However, the excess in NO closely balances the deficit in
N02 response, and consequently the relative accuracy for NOx is good, i.e., about 14 percent for
Unit A and 16 percent for Unit B (Table 6-17).
Table 6-17. Relative Accuracy of Enerac 3000E Analyzers
Unit A
Unit B
NO
no2
NOx
NO
no2
NOx
Source
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
(ppm)
Gas Rangetop
16.12*
105.04
22.68
27.41
105.04
20.68
(5 ppm NO, 2 ppm N02)***
(1.04)**
(1.82)
(0.86)
(2.81)
(1.82)
(1.77)
Gas Water Heater
9.02
110.13
16.23
3.35
110.13
11.04
(60 ppm NO, 5 ppm N02)
(0.60)
(3.67)
(0.71)
(0.65)
(3.67)
(0.78)
Diesel Generator-High RPM
64.91
77.85
13.91
74.82
90.56
16.40
(95 ppm NO, 50 ppm N02)
(1.25)
(0.54)
(0.68)
(1.18)
(1.91)
(0.40)
Diesel Generator-Idle
(280 ppm NO, 115 ppm N02)
Not calculated—
-see text
* Relative accuracy calculated using equation 7.
** Standard error of relative accuracy value, estimated using equation 8.
*** Approximate NO and N02 levels from each source; see Tables 6-16a through d.
This behavior is believed to be related to the sampling probes used with the Enerac analyzers.
Specifically, each analyzer had a fritted metal filter on the tip of its probe, and those filters were
made of Hastelloy®, an alloy that contains about 6 percent molybdenum. Molybdenum is known
to reduce N02 to NO, and, in fact, is used for that purpose in commercial chemiluminescent NOx
monitors. At the temperature of the diesel exhaust under high RPM conditions (400°C, 752°F, or
more based on previous measurements), it is believed that the Enerac fritted filters reduced most
of the N02 present to NO, artificially lowering the former while raising the latter. Additional N02
reduction may have come from reaction of N02 with carbon, trapped as soot in the fritted filter.
This hypothesis accounts for the poor but offsetting accuracies seen for NO and N02, and the
good accuracy seen for NOx, in the high RPM diesel test (Tables 6-16c and 6-17). This hypothesis
has been confirmed by Enerac staff in laboratory tests conducted with the fritted filters after the
verification testing. It should be noted that stainless steel filters are also available for the Enerac
probes, and are expected to be less subject to N02 reduction at the temperatures encountered.
Also, it is unclear whether this reduction of N02 played a role in the failure of the Enerac
analyzers to detect N02 from the two gas sources (see above).
In verification testing with the diesel at idle, exhaust gas temperatures were much lower, and no
error from N02 reduction would be expected. This appears to be the case, as Table 6-16d indi-
cates that both NO and N02 readings from the Enerac analyzers were higher than those from the
reference analyzers. The reason for the consistently higher NO and N02 readings from the Enerac
units in the diesel idle test is not entirely known. The NO and NOx levels determined by the refer-
ence analyzers in this test were within the range of those in previous tests with this engine, as
were those determined by the Enerac analyzers. Thus, there is no obvious reason to distrust either
the reference or Enerac results. Furthermore, as will be shown in the next section, the Enerac ana-
48
-------
lyzers gave good performance in analysis of the zero and span gases during source testing.
However, several lines of argument raise concern about the reference measurements in the diesel
idle test.
One line of argument is that the discrepancy between Enerac and reference results was very nearly
the same (i.e., 20 to 25 percent) for both NO and N02, with both Enerac Units A and B. This
discrepancy also persisted throughout the one-hour continuous sampling of diesel emissions (Sec-
tion 6.2.3) that followed the nine-point accuracy test in Table 6-16d. These observations are
suggestive of, and would be consistent with, the presence of a leak in the inlet line to the reference
analyzers during the diesel idle testing, resulting in dilution of the sample with room air.
Unfortunately, oxygen measurements (which could have indicated the presence of a leak) were
not made in the verification test. Thus, direct confirmation of a leak during the diesel idle test
does not exist. However, indirect evidence does suggest that the quality of the reference analyzer
data was affected during the diesel idle test. One form of such evidence is the unit-to-unit
agreement between the two Enerac analyzers, and between the two reference analyzers, in the
source testing. For example, the average NO or NOx values determined by Enerac Units A and B
on the gas rangetop, gas water heater, and diesel engine at high RPM agreed within 5.45, 6.19,
and 2.89 percent, respectively. The corresponding agreement between the two reference analyzers
for NOx was 6.09, 6.23, and 2.14 percent, respectively (i.e., very similar to the results from the
Enerac analyzers). In contrast, in the 9-point diesel idle test, (Table 6-16d) the Enerac analyzers
agreed within 0.44 percent, and the reference analyzers only within 3.65 percent. During the
subsequent one-hour continuous test, the corresponding unit-to-unit agreement was 1.98 percent
for the Enerac analyzers and 4.67 percent for the reference analyzers. Similarly, the correlation of
data from the two reference analyzers was lower than was the case in other tests with the same
diesel source. For example, in testing of three other vendors' analyzers for an hour continuously
on the diesel source at idle, the reference analyzers showed inter-unit correlation coefficients of
0.98 to 0.99 for NO, and 0.89 to 0.94 for NOx. In contrast, in testing of the Enerac analyzers on
that source (Table 6-20) the reference NO and NOx correlation coefficients were only 0.82 and
0.85, respectively. The data are not wholly conclusive; for example, inter-unit correlation of the
two reference analyzers in the 9-point diesel idle test (Table 6-16d) was actually better for NO,
N02, and especially NOx than the corresponding inter-unit correlations from the Enerac analyzers.
However, the data do suggest that the reference analyzer data in the diesel idle test were not of
the same quality as in the other tests and, for this reason, no relative accuracy results are shown
for this test in Table 6-17.
The unit-to-unit precision of the Enerac 3000E analyzers was very good and, in some cases, was
better than that of the reference analyzers. The Enerac unit-to-unit precision for NO from the gas
range and water heater was 5.45 percent and 6.19 percent, respectively (the Enerac analyzers
failed to detect N02 from those sources). The Enerac unit-to-unit precision for NOx from the
diesel source at high RPM and at idle was 2.89 percent and 0.44 percent, respectively. These
values compare favorably to the corresponding unit-to-unit precision values of the reference
analyzers for NOx of 6.09, 6.23, 2.14, and 3.65 percent, respectively. These results indicate a high
degree of consistency in the behavior of the Enerac analyzers in source measurements. It should
also be noted that this behavior was achieved with NO, N02, and NOx emission levels in the low
end of the Enerac 3000E's measurement range.
49
-------
6.2.2 Zero and Span Drift
Table 6-18 shows the data from the combustion source tests used to evaluate zero and span drift
of the Enerac 3000E analyzers. Note that any NO zero readings below 3 ppm were forced to zero
by the operating mode of the Enerac analyzers.
Table 6-18. Data Used to Assess Zero and Span Drift for Enerac 3000E Analyzers on
Combustion Sources
Unit A NO
Unit A N02
Unit B NO
Unit B N02
Source
(ppm)
(ppm)
(ppm)
(ppm)
Gas Rangetop*
Pre-Test Zero
0
0
0
0
Pre-Test Span
20
9
20
8
Post-Test Zero
0
0
0
0
Post-Test Span
19
9
18
8
Gas Water Heater* *
Pre-Test Zero
0
0
0
0
Pre-Test Span
103
14
102
13
Post-Test Zero
0
0
0
0
Post-Test Span
109
13
107
12
Diesel-High RPM***
Pre-Test Zero
0
0
0
0
Pre-Test Span
199
49
199
49
Post-Test Zero
0
0
3
0
Post-Test Span
204
49
204
49
Diesel-Idle****
Pre-Test Zero
0
0
0
0
Pre-Test Span
405
104
404
106
Post-Test Zero
3
0
6
0
Post-Test Span
402
97
400
101
*Span values 20 ppm NO and 10 ppm N02.
**Span values 100 ppm NO and 15 ppmN02.
***Span values 200 ppm NO and 50 ppm N02.
****Span values 400 ppm NO and 100 ppm N02.
50
-------
Table 6-19 summarizes the zero and span drift observed over each combustion test, in terms of
the pre-test minus post-test differences in zero and span responses. Zero drift for N02 was zero in
all combustion tests with both Enerac units. Zero drift for NO was zero on the gas combustion
sources, but increased to as much as 6 ppm on Unit B with the diesel at idle. Small zero drifts may
be somewhat obscured for NO because of the operating mode, which forces readings below 3
ppm to be reported as zero.
Table 6-19. Results of Zero and Span Drift Evaluation for Enerac 3000E 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
1
0
2
0
Gas Water Heater
Zero
0
0
0
0
Span
-6
1
-5
1
Diesel Generator-High RPM
Zero
0
0
-3
0
Span
-5
0
-5
0
Diesel Generator-Idle
Zero
-3
0
-6
0
Span
3
7
4
5
Span drift for N02 with both analyzers was within 1 ppm on all sources except the diesel at idle.
The 1 ppm span drift on the water heater amounts to 6.7 percent of the 15 ppm N02 span concen-
tration. The N02 span drifts in the diesel idle test are 5 and 7 percent of the 100 ppm N02 span.
For NO, the span drift values in Table 6-19 are equivalent to 5 to 10 percent of the NO span value
in the gas rangetop test, 5 to 6 percent of the NO span in the water heater test, 2.5 percent of
span in the diesel high RPM test, and 1 percent or less of the NO span in the diesel idle test.
6.2.3 Measurement Stability
Table 6-20 shows the data obtained in the extended sampling test, in which the Enerac 3000E and
reference analyzers sampled diesel emissions at engine idle for a full hour without interruption or
sampling of ambient air. The Enerac data were compared to the average of the reference analyzer
data to assess whether a different trend in the emission data was observed for the Enerac
analyzers relative to the reference analyzers. 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 indicated by the Enerac analyzers differed from
those observed by the reference analyzers.
51
-------
Table 6-20. Data from Extended Sampling Test with Diesel Generator at Idle, Using Enerac 3000E Analyzers
Unit A NO
(ppm)
Unit A N02
(ppm)
Enerac Analyzer Data
Unit A NOs Unit B NO
(ppm) (ppm)
Unit B N02
(ppm)
Unit B NOx
(ppm)
14ANO
(ppm)
14A N02
(ppm)
Reference Analyzer Data
14A NOs 10 NO
(ppm) (ppm)
10 no2
(ppm)
10 NOx
(ppm)
1
336
144
480
346
141
487
286.3
122.5
408.8
279.6
112.7
392.3
2
335
144
479
346
142
488
285.5
123.4
409.0
279.6
111.7
391.3
3
333
145
478
343
143
486
285.8
123.1
408.9
279.6
111.7
391.3
4
335
145
480
344
143
487
281.7
125.7
407.4
277.7
112.7
390.5
5
335
145
480
348
143
491
287.0
124.0
410.9
280.5
112.7
393.3
6
333
146
479
343
143
486
284.3
127.1
411.4
277.7
115.8
393.6
7
329
145
474
338
143
481
279.8
124.5
404.4
274.0
113.8
387.8
8
333
145
478
343
143
486
285.1
122.8
407.9
279.6
109.6
389.2
9
329
145
474
340
143
483
282.6
124.6
407.2
275.9
110.7
386.5
10
326
146
472
335
144
479
277.3
124.1
401.3
272.1
111.7
383.8
11
324
146
470
335
144
479
281.8
123.5
405.3
274.0
110.6
384.7
12
326
146
472
336
145
481
280.4
121.8
402.2
274.9
110.6
385.6
13
325
145
470
335
145
480
277.0
121.9
398.9
270.3
112.7
383.0
14
322
145
467
333
144
477
279.0
120.0
398.9
271.2
111.7
382.9
15
326
146
472
338
145
483
277.9
120.8
398.8
274.0
110.6
384.7
16
327
146
473
338
145
483
280.1
119.9
400.0
274.0
110.6
384.7
17
328
146
474
340
145
485
280.9
123.3
404.2
275.9
111.7
387.6
18
329
146
475
341
145
486
281.1
124.9
406.0
274.0
111.7
385.7
19
329
146
475
338
146
484
279.9
123.9
403.8
274.9
111.7
386.6
20
332
147
479
341
146
487
282.1
123.0
405.1
274.9
112.7
387.7
21
329
146
475
341
145
486
283.5
122.5
406.0
275.9
112.7
388.6
22
333
146
479
341
145
486
284.5
122.4
406.9
275.9
114.8
390.7
23
329
146
475
340
145
485
281.1
124.1
405.3
274.9
114.8
389.7
24
326
146
472
336
145
481
279.6
125.9
405.5
273.1
115.8
388.9
25
325
146
471
336
145
481
278.3
124.2
402.5
271.2
114.8
386.0
26
326
147
473
338
145
483
278.9
119.0
397.9
272.1
114.8
386.9
27
327
147
474
338
145
483
279.9
118.4
398.3
272.1
112.7
384.9
28
328
146
474
336
145
481
281.6
123.6
405.2
274.0
113.8
387.8
29
329
146
475
340
145
485
282.1
123.8
405.9
274.0
113.8
387.8
30
332
147
479
343
145
488
282.7
124.5
407.2
274.9
112.7
387.7
-------
Table 6-20. Data from Extended Sampling Test with Diesel Generator at Idle, Using Enerac 3000E Analyzers (continued)
Unit A NO
(ppm)
Unit A N02
(ppm)
Enerac Analyzer Data
Unit A NOs Unit B NO
(ppm) (ppm)
Unit B N02
(ppm)
Unit B NOx
(ppm)
14ANO
(ppm)
14A N02
(ppm)
Reference Analyzer Data
14A NOs 10 NO
(ppm) (ppm)
10 no2
(ppm)
10 NOx
(ppm)
31
334
147
481
343
145
488
283.6
127.9
411.5
274.9
117.9
392.9
32
330
146
476
341
145
486
281.7
126.8
408.5
274.9
116.9
391.8
33
333
146
479
343
145
488
283.0
126.4
409.4
274.0
116.9
390.9
34
334
147
481
346
146
492
284.5
123.5
408.0
274.9
115.8
390.8
35
335
149
484
346
147
493
288.0
125.0
413.0
278.7
115.8
394.5
36
338
149
487
348
147
495
290.2
123.5
413.7
279.6
114.8
394.4
37
337
148
485
348
147
495
289.0
127.1
416.2
280.5
115.9
396.4
38
333
148
481
346
147
493
288.3
125.8
414.1
277.7
116.9
394.6
39
335
148
483
346
148
494
286.9
126.3
413.2
277.7
115.8
393.6
40
334
149
483
343
147
490
289.3
124.6
413.9
277.7
116.9
394.6
41
333
149
482
346
147
493
287.9
126.2
414.1
276.8
116.9
393.7
42
333
148
481
343
147
490
284.0
129.7
413.7
275.9
116.9
392.8
43
332
149
481
343
148
491
282.4
130.5
412.8
276.8
115.8
392.7
44
332
149
481
343
148
491
283.6
127.9
411.5
275.9
115.8
391.7
45
331
149
480
341
148
489
288.9
123.9
412.8
276.8
115.8
392.7
46
329
148
477
338
147
485
282.4
129.4
411.7
274.9
114.8
389.7
47
324
147
471
336
147
483
279.8
129.0
408.8
273.1
114.8
387.9
48
329
147
476
340
147
487
279.8
129.0
408.8
271.2
116.9
388.1
49
326
148
474
336
147
483
282.0
127.6
409.6
272.1
116.9
389.0
50
325
148
473
336
147
483
282.8
126.6
409.4
272.1
116.9
389.0
51
324
147
471
335
147
482
280.8
126.8
407.5
271.2
115.8
387.0
52
326
147
473
336
147
483
281.8
125.6
407.4
271.2
115.8
387.0
53
324
147
471
335
147
482
279.6
127.0
406.6
271.2
114.8
386.0
54
324
147
471
336
147
483
278.9
127.9
406.8
269.3
115.8
385.2
55
326
147
473
338
146
484
279.5
129.3
408.9
271.2
115.8
387.0
56
327
147
474
338
146
484
282.6
127.9
410.6
272.1
117.9
390.1
57
324
146
470
333
145
478
278.5
129.4
407.9
270.3
116.9
387.2
58
322
145
467
332
145
477
279.2
126.3
405.5
269.3
114.8
384.1
59
324
145
469
336
145
481
280.0
127.7
407.7
270.3
114.8
385.1
60
326
146
472
335
145
480
279.8
129.0
408.8
270.3
115.8
386.1
-------
Table 6-21 indicates that both the Enerac analyzers and the reference analyzers showed a gradual
decrease in NO and an increase in N02 during the 1-hour sampling period. For NO, there was no
difference statistically between the trend shown by the two Enerac analyzers and that shown by
the reference analyzers. However, for N02, both Enerac analyzers showed a lower rate of increase
(i.e., a smaller positive slope) than did the reference analyzers, and the small differences were
statistically significant. As a result, a statistically significant difference was also found in the slopes
for NOx. Overall, the reference analyzers showed a slight increase in NOx emissions from the
diesel engine during the extended sampling, whereas the Enerac analyzers showed a slight
decrease or essentially no change. However, though statistically significant differences are shown
in Table 6-21, their practical significance is negligible. For example, the reference analyzers
indicate an upward trend in NOx of 0.052 ppm/min, or 3.1 ppm per hour, whereas the two Enerac
analyzers indicate NOx trends of -0.029 ppm/min (-1.7 ppm/hr) and 0.003 ppm/min (0.2 ppm/hr)
respectively. Considering that the diesel engine emitted approximately 400 ppm of NOx, these
slight differences in slope are negligible, amounting to a difference of less than 5 ppm, or about
1 percent of the source output, over 1 hour of sampling.
Table 6-21. Results of Evaluation of Measurement Stability for Enerac 3000E Analyzer
Unit A
Unit B
Reference Units
NO
no2
NOx
NO
no2
NOx
NO N02 NOx
Slope
-0.073
0.044
-0.029
-0.066
0.069
0.003
-0.047 0.099 0.052
(Std Err)
(0.030)
(0.008)
(0.035)
(0.031)
(0.008)
(0.034)
(0.022) (0.011) (0.027)
Difference in Slopes
(ppm/min)
-0.026
-0.056
-0.081
-0.019
-0.030
-0.049
— — —
(Std Err)
(0.015)
(0.013)
*
(0.017)
*
(0.015)
(0.014)
*
(0.019)*
* Statistically significant difference in slope among test unit and the averages of the reference units at the
5 percent significance level.
6.2.4 Inter- Unit Repeatability
The repeatability of test results between the two Enerac 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 Enerac 3000E units at the 95 percent
confidence level. As Table 6-22 shows, statistically significant differences between Units A and B
were found in the regression intercept, detection limits, relative accuracy, and measurement
stability, primarily for NO and NOx. The differences found indicate the variability that may be
expected from one analyzer to the next. However, although some statistically significant
differences were found between the two analyzers, the practical importance of those differences is
negligible. Overall, the test results do not show any significant difference in performance between
Enerac Units A and B.
54
-------
Table 6-22. Summary of Repeatability
Unit A vs. Unit B
NO
no2
NOx
Linear
Intercept
t-statistic
1.529
0.363
...
Regression
p-value*
0.157
0.724
...
(Test 1)
Slope
t-statistic
-1.926
-0.018
...
p-value
0.083
0.986
...
Linear
Intercept
t-statistic
-2.674
—
—
Regression
p-value*
0.023
...
...
(Test 2)
Slope
t-statistic
2.032
...
...
p-value
0.070
...
...
Linear
Intercept
t-statistic
0.652
—
—
Regression
p-value*
0.529
...
...
(Test 3)
Slope
t-statistic
-1.105
...
...
p-value
0.295
...
...
Detection Limit (a)
t-statistic
-3.162
0.001
...
p-value
0.004
1.000
...
Detection Limit (b)
t-statistic
2.659
...
...
p-value
0.013
...
...
Detection Limit (c)
t-statistic
***
...
...
p-value
***
...
...
Relative
Gas Rangetop
t-statistic
2.000
***
2.000
Accuracy
p-value
0.081
...
0.081
Gas Water
t-statistic
20.239
***
20.239
Heater
p-value
<0.001
...
<0.001
Generator-
t-statistic
6.526
4.793
5.231
High ppm
p-value
<0.001
0.001
<0.001
Generator-
t-statistic
15.751
6.425
1.603
Idle
p-value
<0.001
<0.001
0.148
Measurement
Slope
t-statistic
-0.783
-5.478
-3.142
Stability
p-value
0.437
<0.001
0.003
* p-value < 0.05 indicates that two test units are statistically different at the 5% significance level.
** Unit A and Unit B had all responses of 0 ppm at c=0. The estimated standard deviations were 0.
The two-sample t-statistic could not be calculated.
*** Unit A and Unit B had exactly the same N02 readings on the gas burner and water heater emissions.
The matched-pairs t-statistic could not be calculated.
6.3 Other Factors
In addition to the performance characteristics evaluated in the laboratory and source tests, three
additional factors were recorded: analyzer cost, data completeness, and maintenance/
operational factors.
55
-------
6.3.1 Cost
The cost of each Enerac 3000E analyzer as used in this verification was about $12,000. This is for
the complete analyzer, including sampling probe and lines, and with the capability for multiple
measurement ranges.
6.3.2 Data Completeness
The data completeness in the verification tests was 100 percent for both units of the Enerac
3000E.
6.3.3 Maintenance/Operational Factors
The duration of the verification tests was not sufficient to determine the long-term reliability or
maintenance costs of the Enerac analyzers. No maintenance problems or delays resulted at any
time, and switching control modules to change the NO range was a simple and rapid operation.
The operational mode of the analyzers in most of the verification tests, in which NO readings
below 3 ppm were forced to zero, will not be appropriate in applications where very low NO
readings are of interest.
It was found that the Hastelloy® fritted inlet filters reduced N02 to NO when sample gas
temperatures were high enough (i.e., a few hundred degrees centigrade). The stainless steel fritted
filters should be used instead, whenever possible. Although the Hastelloy® filters do not appear
to affect the total NOx content of the sample, they can radically alter the proportions of NO and
N02 in the sample.
56
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Chapter 7
Performance Summary
The two Enerac 3000E analyzers provided linear response for NO over their full operating ranges,
including the basic 0 to 1,000 ppm range, and extended (0 to 3,000 ppm) and reduced (0 to 300
ppm) ranges. For N02, response was linear over a tested range of 0 to 400 ppm. The detection
limit for N02 was about 6 ppm on both analyzers. Determination of detection limits for NO was
complicated by an operational mode of the analyzers that forced readings below 3 ppm to be
reported as zero. In different linearity tests, NO detection limits of 4.9 ppm and 1.2 ppm were
found for Unit B, and a detection limit of about 8 ppm was found for Unit A. The response times
of both analyzers for NO were about 60 seconds, and for N02 were about 100 seconds.
Drift in zero readings was usually 4 ppm or less over the course of a variety of laboratory and
combustion source tests, on both the NO and N02 sensors of both analyzers. The only exceptions
were zero drift values of 7 ppm and 12 ppm for NO, as a result of an NO linearity test up to 3,000
ppm. Within a single day, span drift was less than 2 percent of the span concentration for NO,
using span concentrations of 700 to 1,000 ppm NO. Similarly, span drift for N02 was less than
2 percent of the span concentration, using span concentrations of 350 to 400 ppm. Shutting the
analyzers off overnight did not increase either zero or span drift. No interference was found from
any of the following: 496 ppm CO, 5.03 percent C02, 494 ppm NH3, 590 ppm of total hydro-
carbons, and 501 ppm S02. When sampling a mixture of 451 ppm S02 and 385 ppm NO, the NO
sensors of the Enerac analyzers indicated 426 ppm and 422 ppm, respectively, suggesting a
positive interference from the S02 equivalent to 8 to 9 percent of the S02 concentration.
Over the range of-10 to +10 inches of water (relative to the ambient pressure), the sample gas
pressure had no significant effect on the zero or span readings of the analyzers. Ambient
temperature over the range of 45 to 105°F (7 to 41 °C) also had no consistent effect on the
zero or span readings.
Relative accuracy of the Enerac analyzers differed in tests on three combustion sources. On two
gas combustion sources having N02 emissions of 2 to 7 ppm, the Enerac analyzers detected no
N02. Relative accuracy for NO on those sources (at NO levels of 5 to 60 ppm) ranged from 3 to
27 percent. On a diesel source at high RPM, the Enerac analyzers read high on NO and low by an
equal amount on N02, apparently because of metal filters on the analyzers' sampling probes,
which reduced N02 to NO. Relative accuracy values for NO and N02 with that source were 65 to
90 percent, but relative accuracy for NOx was about 14 and 16 percent on the two analyzers,
respectively. In sampling of a diesel source at idle, the Enerac analyzers performed well, but
uncertainty about the quality of the reference data prevented calculation of relative accuracy.
57
-------
Overall, the relative accuracy found for NOx measurements with the two analyzers ranged from 11
to about 20 percent for all sources.
The two Enerac analyzers provided essentially identical performance in all aspects of the
verification test. The unit-to-unit precision of the two Enerac analyzers ranged from 0.4 to
6.2 percent on the four combustion sources and, in some cases, was better than that of the
reference analyzers.
58
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Chapter 8
References
1. Test/QA Plan for Verification of Portable NO/NO 2 Emission Analyzers, Battelle, Columbus,
Ohio, December 1998.
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 Usedfor Calibrations
and Audits of Continuous Source Emission Monitors: Protocol Number 7, 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 NO 2 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 Standard (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).
59
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Appendix A
Data Recording Sheets
A-l
-------
Date:
Linearity Test Data Sheet
_ Vendor/Analyzer: _
Form Filled Out By:
Pre-Test Z/Span: Unit A: Zero (NO/NO2)
UnitB: Zero(NO/N02)
NO Test
Unit A
(NO/NO2)
UnitB
(NO/NO2)
1.
2.
3.
4.
5.
Time Response 6.
7.
Span (NO/NO2) !_
Span (NO/NO2) /
NO? Test
Unit A
(NO/NO2)
Unit B
(NO/NO2)
4.
7.
9-
10..
11-.
12..
13..
14..
15..
16..
17..
18..
19..
20..
21.
9.
10.
11.
1Z.
13.
14.
15.
16.
17.
18.
19.
20.
21.
Post-Test Z/Span: Unit A: Zero (NO/NO2) / Span(NO/N02) /
UnitB: Zero(NO/N02) / Span(N0/N02) /
-------
Interrupted Sampling Data Sheet
Form Filled Out By:
Pre-Shut Down Z/'Span:
Date: ^ Time:
Unit A (NO/NO2) Zero / Span /
Unit B (NO/NO2) Zero / Span /
Post-Shut Down Z/Span:
Date: Time:
Unit A (NO/NO2) Zero / Span /
Unit B (NO/NO2) Zero / Span /
-------
Date:
Form Filled Out By:
Interference Test Data Sheet
Vendor/Analyzer:
Interference Gas
Zero
CO
Zero
co2
Zero
NH3
Zero
Hydrocarbons
Zero
S02
Zero
S02 + N0
Concentration
496 ppm
5.03%
494 ppm
590 ppm
501 ppm
451 ppm + 393 ppm
Response fNO/NQ?)
Unit A UnitB
-------
Flow Rate Sensitivity Data Sheet
Date:
Vendor/Analyzer:
Form Filled Out By:
Flow Rate Data:
Response Data:
Ambient P
Unit A
fecm>
Unit B
fccm)
Ambient P
+10inH2O
-lOinHiO
+10inH2O
Unit A
(NO/NO/)
UnitB
(NO/NO^
Zero
NO Span
Zero
NO2 Span
Zero
Zero
NO Span
Zero
NO2 Span
Zero
-10 in H20 Zero
/
/NO Span
Zero
NO2 Span
Zero
-------
Ambient Temperature Test Data Sheet
Date: Vendor/Analyzer:
Form Filled Out By:
Room Temperature: Response (NO/NCM
Unit A UnitB
Zero / /
NO Span / /
NO2 Span / /
Zero / /
Cold Chamber Temperature:
Zero / /
NO Span / /
NO2 Span / L
Zero / !_
Heated Chamber Temperature:
Zero / !_
NO Span / /
NO2 Span / /
Zero / L
Room Temperature:
Zero
NO Span
NO2 Span
Zero
-------
Accuracy Test Data Sheet: Rangetop Combustion
Date Vendor Analyzer
Form Filled Out By:
Pre-Test Zero/Span
Calibration Gas & Concentration: Instrument Range:
Calibration Gas & Concentration: Instrument Range:
Unit 14A: Zero (N0/N02/N0x) / / Span (N0/N02/N0x)
Unit 10: Zero (N0/N02/N0x) / / Span (N0/N02/N0x) _/_/
Unit 14A Unit 10
(N0/N02/N0x)
-------
Accuracy Test Data Sheet: Water Heater Combustion
Date
Vendor Analyzer:,
Form Filled Out By:.
Pre-Test Zero/Span
Calibration Gas & Concentration: Instrument Range:_
Calibration Gas & Concentration: Instrument Range:_
Unit A: Zero (N0/N02/N0x)
Unit B: Zero
-------
Accuracy Test Data Sheet: Diesel-Engirie Combustion
Date Vendor Analyzer
Form Filled Out By:
Pre-Test Zero/Span
Calibration Gas & Concentration: Instrument Range:
Calibration Gas & Concentration: Instrument Range:
Unit 14A: Zero (N0/N02/N0x) / / Span (N0/N02/N0x)
Unit 10; Zero (N0/N02/N0x) / / Span (N0/N02/N0x)
Unit 14A Unit 10
(N0/N02/N0x) (N0/N02/N0x)
1. / / /
2. I / /
3. I / /
4. / / /.
5. / / /
6. / / i
1. / I /_
8. / / /_
9.11 /
Post-Test Zero/Span
Calibration Gas & Concentration: Instrument Range:
Calibration Gas & Concentration: Instrument Range:
Unit 14A: Zero (N0/N02/N0x) / I Span (N0/N02/N0x)
Unit 10: Zero (N0/N02/N0x) / / Span (NO/N02/NOx)
Mo-1: 01/17/99
-------
Measurement-Stability Test Data Sheet: Diesel-Engine Combustion
Date Vendor Analyzer
Form Filled Out By:
Diesel-Engine Load:
Time Unit A
(t+min#) (N0/N02/N0x)
1. / /
2. / /
3. / /
4. / /
5. / /
6- / /
7. / /
8- / /
9. / /
10. / /
11. / /
12- / /
13: / /
14. / /
15. / /
16. / /
17. / /
18- / /
19- / /
20. / /
21. / /
22 / /
23. / /
24. / /
25. / /
26. / /
27. / /
28. / /
29. / /
Unit B
(NO/NOz/NOx)
30.
-------
Date
Measurement-Stability Test Data Sheet: Diesel-Engine Combustion
Vendor Analyzer:
Form Filled Out By:_
Diesel-Engine Load:_
Time
(t + min#)
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
41.
42.
43.
44.
45.
46.
47.
48.
49.
50.
51.
52
53.
54.
55.
56.
57.
58.
59.
60.
Unit A
(N0/N02/N0x)
Unit B
(N0/N02/N0x)
-------
Appendix B
External Technical Systems Audit Report
B-l
-------
Environmental Technology Verification Program
Advanced Monitoring Systems Pilot
Air Monitoring Systems
N0/N02 Monitors Verification Test
January 20-21,1999 Audit
Audit Report: ETVAMS001
Revision!
) Elizabeth A. Betz
zabeth T. Himike
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ETV AMS Air Audit
Page 1
1.0 Audit Information
1.1 Auditors:
Elizabeth A. Betz
Human Exposure & Atmospheric Sciences Division
U. S. EPA, NERL (MD-77)
Research Triangle Park, NC 27711
(919)541-1535
Elizabeth T. Hunike
Atmospheric Methods & Monitoring Branch
Human Exposure & Atmospheric Sciences Division
U. S. EPA, NERL (MD-46)
Research Triangle Park, NC 27711
(919) 541-3737
1.2 Dates of Audit: January 20-21, 1999
1.3 Location of Audit: Battelle Memorial Institute, Columbus, Ohio
1.4 Battelle Staff Interviewed and/or Observed:
Karen Riggs ETV AMS Pilot Manager
Susan Abbgy QA/QC Reviewer
Sandy Anderson QA Manager
Verification Test Team:
Tom Kelly Verification Test Leader
Joe Tabor Laboratory Verification Testing
Jim Reuther Emission Source Verification Testing
Steve Speakman Operator, Emission Sources/Reference Method
2.0 Background
Throughout its history, the U.S. EPA has evaluated technologies to determine their effectiveness in
preventing, controlling, and cleaning up pollution. EPA has expanded these efforts by instituting the
Environmental Technology Verification Program (ETV) to verify the performance of a larger number of
innovative technical solutions to problems that threaten human health or the environment. The goal of
ETV is to verify the environmental performance characteristics of commercial-ready technology through
the evaluation of objective and quality assured data, so that potential purchasers and permitters are
provided with an independent and credible assessment of what they are buying and permitting. The
ETV Program Verification Strategy outlines the goals, operating principles, pilot selection criteria, and
implementation activities. ETV includes twelve pilot projects. In these pilots, EPA is using the
expertise of partner verification organizations to design efficient processes for conducting performance
tests of innovative technologies. The implementation activities involve forming stakeholder groups who
identify technologies needing verification, designing a generic verification protocol and then Test/QA
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ETV AMS Air Audit
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Plans for the specific technology to be verified. The verification tests are run on the identified
technologies wishing to participate and verification statements based on the test results are generated.
One pilot, entitled Advanced Monitoring Systems (AMS), is to verify the performance of commercially
available technologies used to monitor for environmental quality in air, water and soil. This pilot is
managed by EPA's National Exposure Research Laboratory in Research Triangle Park, North Carolina
and their verification partner for the AMS pilot project is Battelle Memorial Institute, Columbus, Ohio.
This pilot has been divided into three sub-pilots, each looking at monitoring systems for a specific
media, air, water and, eventually, soil. The Air AMS portion has evolved to the point of actually
running verification tests on available air monitoring instrumentation.
3.0 Scope of Audit
3.1 Audit Preparation. The auditors reviewed the following documents pertinent to the ETV AMS
Pilot:
a. Environmental Technology Verification Program Quality and Management Plan for the
Pilot Period (1995-2000), May 1998
b. Environmental Technology Verification Program Quality Management Plan for the
ETV Advanced Monitoring Systems Pilot, September 1998
c. Test/QA Plan for Verification of Portable NO/NO 2 Emission Analyzers, December 4,
1998
d. U. S. EPA Method 6C, Determination of Sulfur Dioxide Emissions from Stationary
Sources (Instrumental Analyzer Procedure)
e. U. S. EPA Method 7E, Determination of Nitrogen Oxides Emissions from Stationary
Sources (Instrumental Analyzer Procedure)
Based on the above material, a checklist was prepared. The U. S. EPA ETV AMS Pilot Manager,
Robert G. Fuerst, was provided the checklist prior to the audit. The completed checklist for this audit is
attached.
3.2 Audit Scope.
The audit encompassed a technical systems audit of a verification test (VT) on nitrogen oxides monitors
at Battelle. A technical systems audit is a qualitative onsite audit of the physical setup of the test. The
auditors determine the compliance of testing personnel with the test/QA plan. The auditors were on site
from Wednesday afternoon through Thursday afternoon. The technical systems audit was performed on
the flow rate and ambient temperature of the laboratory portion of the VT and the relative accuracy
tests with the gas cooktop, water heater and a portion of the lower range emissions of a diesel
generator. No performance evaluations were conducted as a part of this audit.
4.0 Executive Summary
4.1 The VT is well-managed, particularly considering its complexity. All personnel appeared to be
well-trained for their particular duties. All involved showed enthusiasm and ingenuity during the VT.
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ETV AMS Air Audit
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4.2 The significant findings of this audit, cited in paragraph 5.0 below, had also been found by
Battelle's QA staff during their audit earlier in the VT.
4.3 The technical systems audit showed that the VT personnel were very familiar with the Test/QA
Plan. With one exception, differences for this VT from the original Test/QA Plan were well
documented by deviation reports on file at Battelle. The deviation report format includes a date, cites
the deviation, provides an explanation of the deviation and requires an approving Battelle signature. It
was impressive that the deviation reports were present and were completed up front. The one
difference from the VT that was not cited in a deviation report was that Battelle had intended to run an
analyzer already on hand completely through the VT before the first vendor's analyzer. This was not
done nor was a deviation report generated. The remaining differences were cited in the deviation
reports.
5.0 Major Findings
5.1 Undocumented Deviation from the Test/QA Plan. The undocumented deviation was from
section 5.6, Test Schedule, and stated "to avoid bias in testing of the first analyzers through the
sequence, Battelle's personnel will first conduct the entire test sequence using an analyzer already on
hand at Battelle. Testing will then continue with analyzers named in section 2.4." Due to a delay in the
arrival of the protocol gases used in the VT, Battelle did not run one of their instruments through the
test sequence. As a result a leak in the gas supply system in the laboratory test portion was not detected
before the first vendor started the VT sequence.
5.2 Initial Calibration of Instruments for Emission Source Testing. The Test/QA Plan states that
"the chemiluminescent monitors to be used for Method 7E reference measurements will be subjected to
a 4-point calibration with NO prior to the start of verification testing, on each measurement range to be
used for verification." The initial Emission's portion of the VT was started on January 13, 1999. There
was no 4-point calibration with NO recorded in the Emission's VT laboratory notebook prior to the
January 13th testing. This finding is also a finding in Battelle's Internal Audit conducted during the first
week of the VT.
6.0 Results of Technical Systems Audit
6.1 Organization. The Battelle ETV AMS VT team consisted of four members. All team members
were very knowledgeable of the procedures and helpful to the auditors. There are also two Battelle
Quality Assurance staff members that are members of the ETV AMS team. Both were available and
very helpful to the auditors. These Battelle QA staff members are responsible for running the internal
audits required by the ETV related QMPs. One such audit was conducted the week prior to this EPA
audit.
6.1.1 The Test/QA Plan stated that a Dr. Agnes Kovacs would be providing statistics and data
analysis for this VT. One of the documented deviations was that Dr. Kovacs would not be participating
in the VT as she has left Battelle. Although the deviation report stated that someone in the Statistics
and Data Analysis Department would be taking her place, there was no indication in the deviation report
as to who it would be.
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ETV AMS Air Audit
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6.2 Gas Cylinder Certifications. A review of the gas cylinder certifications uncovered some minor
discrepancies. The expiration date on two of the cylinder certifications did not match the expiration
date on the cylinders. The discrepancy was corrected by the gas manufacturer on the day of inspection.
Battelle did not initially have certifications for the gas cylinders used in the source test. The gas
manufacturer was contacted by phone and faxed in certifications for 3 of the 4 cylinders. The original
certificates were later located on one of the team member's desk. The gas cylinder for one of the
certificates reviewed was not found among the ETV VT equipment.
6.3 Temperature Sensor Certification. The certificate in the notebook maintained for the Laboratory
Test Portion was for Model 402A, Serial # 40215 Temperature Indicator. This indicator was not seen
by the Auditors. The Temperature Indicator used in the Laboratory Test portion to read the
temperature of the monitors during the Ambient Test was Model 400A, decal # LN-560558. The
certificate was not in the notebook, however, the indicator did have a label on it that stated that it was
certified 1-7-99. Discussion with Susan Abbgy, after the audit, clarified that LN-560558 was an internal
Battelle laboratory number and that the manufacturer's serial number on LN-560558 was 40215.
However, the certificate did reflect an incorrect model number for Temperature Indicator Serial #
40215.
6.4 Deviation Reports. The dated reports cited the deviation, provided an explanation/justification of
the deviation and required an approving Battelle signature. It was impressive that the deviations reports
were present and were completed up front.
6.4.1 The Flow Rate Sensitivity Test procedure had three deviation reports. The Test/QA Plan
called for the use of 60% span value during the test. A deviation report cited that this was changed to
70% span value to correlate to the Linearity Test. The two other reports related to the Flow Rate
Sensitivity Test were very similar and called for a change in the order of the procedure to reduce the
amount of plumbing changes required.
6.4.2 The Ambient Temperature Test had one deviation report. The order of the test was
changed. The procedure called for doing a cooled chamber test first and then hot. The deviation report
stated that all VTs will be done in the reverse order. The reason for the deviation was based on
discussions with the vendors that indicated the rise in temperature after exposure to NO may cause
more drift. The order was reversed to more clearly observe any drift.
6.4.2.1 During the Ambient Temperature Test observed, slight changes were made to
accommodate the mass of the monitors. The vendor's monitors were larger than previous monitors and
generated and held heat longer. The door to the heated chamber, once the monitors reached its
temperature, had to remain slightly ajar to hold the chamber temperature at a constant value. The
heated monitors were then placed in the cold chamber (a standard household refrigerator). The heat
given off by the monitors raised the temperature in the refrigerator over 100°F. To obtain a cooled
chamber reading the team members relocated the monitors to the outdoors which produced a cooled
ambient temperature within the 45°F ±5°F for the one hour required for temperature equilibration and
the additional time required to perform the zero and span check. This was a fine example of the
ingenuity the VT team members showed to accommodate differences in monitors.
6.4.3 Interference Test. The mixture of S02 and NO for the Interference Test was changed
from interferant levels of 250 ppm each of S02 and NO to interferant levels of 451 ppm S02 and 393
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ETV AMS Air Audit
Page 5
ppm NO. According to the deviation report, this change was made because the NO standard available
wasn't at the anticipated concentration when the Test/QA Plan was written.
6.4.4 Source Testing.
6.4.4.1 The Test/QA Plan cited the use of two diesel generators for the Source Test.
The selection of these generators was made based on studies that Battelle had used in the past that
provided a database of emission levels generated by these sources. However, these generators were
property of the Air Force and were unavailable at the time of the VT due to military activities in the
Middle East. Battelle substituted one generator they had on site and collected emission data at two
speeds to provide two higher emission levels than previously provided by the cooktop or water heater.
This substituted generator produced two levels of emissions; however, neither level was over 500 ppm
of NO. The database that Battelle had on the originally planned generators showed that one model
would produce ranges between 100-1000 ppm NOx and the second model would produce ranges
between 600-2300 ppm NOx. The impact of this change is that there will be no verification for higher
ranges.
6.4.4.2 The oxygen sensor was not used during the source test. This VT's focus was
the verification of NO/N02 levels and not to compare oxygen data. Source stability will be documented
by NOx measurements instead of oxygen measurements. The source stability for the water heater and
the cooktop is also documented in two Battelle reports on data from these specific sources used in
interlaboratory comparisons from 1994 through 1998. The initial generators planned for the VT also
had similar data bases. The source stability of the generator actually used was verified by data collected
in December and January prior to the VT. The actual data collected by the reference monitors during
the VT also verified the source stability.
6.4.4.3 ThermoEnvironmental Models 14A and 10 NO/N02 analyzers were used for the
reference method. The Test/QA Plan called for identical Beckman Model 955 monitors. The reason
stated in the deviation report for the substitution was that the Thermo Instruments are newer and are in
more current use.
6.4.4.4 Triplicate readings of calibration points were not run in the calibration of the
reference method analyzers. Method 7E does not require triplicate readings of calibration points.
6.4.4.5 One deviation report addressed the use of unheated sample lines and poly tubing.
The Test/QA Plan is based on EPA Method 7E but based on Battelle's own experience with the sources
in the laboratory environment an unheated inlet was used. Additionally it should be noted that the VT is
conducted inside in a laboratory setting with controlled temperature and humidity and Method 7E is for
stack sampling. The only comment on this deviation report is that the originator of the deviation signed
the report instead of obtaining an independent approval signature.
6.5 Leak Detected in the System in the Laboratory Test Portion. During the first vendors's
laboratory test portion, a leak was detected in the system. The data sheets for the laboratory test
portion of the first vendor's VT showed a note that a leak was detected and the vendor recorded
oxygen levels. Also noted on the data sheet was a correction factor that would be used on the vendor's
data that was made based on the vendor's oxygen readings. The correction factor notes were brought
to the auditor's attention by Battelle's QA staff. Because the VT did no verification of oxygen levels,
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ETV AMS Air Audit
Page 6
the correction factor may be inaccurate. As part of the documentation for that VT, the accuracy of the
oxygen readings by the vendor needs to be addressed.
6.6 Initial Calibrations and Tests in the Source Laboratory. As stated under major findings,
paragraph 5.2 above, the initial calibrations of the chemiluminescent monitors used as the Method 7E
references were not done before the first VT. In addition no interference test was conducted prior to
1-18-99 which was after the second VT. However, all subsequent VTs had the required initial
calibration and interference tests. This was also a finding in Battelle's internal audit conducted a week
earlier. Battelle will need to address this in the VT report.
6.7 Corrections of Data Sheets. In most instances, corrections made on the data sheets followed
Good Laboratory Practices; however, some did not (i.e., one line was not drawn through the incorrect
entry and the correction was not dated and initialed).
6.8 Source Laboratory Notebook Entries. The initial entries were difficult to follow because the
writing was almost illegible and there were missing entries. However, with the exception of the first
VT, the four-point initial calibrations are recorded and the time and dates of the VTs are also shown.
The actual source test data are recorded on data sheets. The notebook is only used to record the
calibration and interference test data on the reference monitors and to record the times, dates and
comments on the VTs.
-------
Checklist for Verification Test (VT) of Portable N0/N02 Emission Analyzers
Date(s): January 20-21. 1999 Location: Battelle. Columbus. Ohio
Personnel Involved in the Audit:
Titles
Names
EPA Auditor(s):
Elizabeth Betz
Elizabeth Hunike
Battelle QA Rep present:
QA/QC Reviewer
Susan Abbgy
QA Manager
Sandy Anderson
Battelle Auditees:
ETV AMS Pilot Manager
Karen Riggs
Verification Test Leader
Tom Kelly
Laboratory Verification Testing
Joe Tabor
Emission Source Verification
Testing
Jim Reuther
Operator, Emission
Sources/Reference Method
Steve Speakman
Vendor(s) Present:
Horiba
J. David Vojtko
General
Comments
Are the Testers familiar with:
ETV QMP
All staff seem familiar with the
documents and there are copies of each
in the ETV reference notebooks
maintained in the Laboratory and
Source Testing areas
Verification Protocol
Test/QA Plan
QA Manager
Generic Verification Protocol:
Finalized?
The Protocol has been finalized and is
in the process of being placed on the
web.
Test Plan:
Approved and Signed?
The test plan has been reviewed by the
vendors. Approval signatures have
been received as vendors have arrived
to participate in the verification test
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ETV AMS Pilot
N0/N02 Checklist
Page 2
Technologies:
-Electrochemical (EC) sensors
Testo's Model 350 electrochemical NO and N02 analyzer
Also by direct measurement: 02, CO, S02, Stack Temperature, Stack Pressure
By calculation: C02
Energy Efficiency System's ENERAC 3000SEM electrochemical NO & N02 analyzer
Also by direct measurement: 02, CO, S02, C02, Stack Temperature
TSI's COMBUCHECK electrochemical NO or N02 analyzer
ECOM's A-Plus electrochemical NO and N02 analyzer
Also by direct measurement: 02, CO, S02, Stack Temperature, Stack Pressure
By calculation: C02
-Chemiluminescence emitted from the reaction of NO with 03 produced within the analyzer
Horiba's Model PG-250 portable gas analyzer
Also by direct measurement: 02, CO, S02, C02
The audit was run during the second week of the Test Plan and the 4th vendor was being verified. The
vendor was Horiba.
Pre-Test Requirements:
Dry Gas Meter: Initial Calibration Date: See Below
Accurate within 1% and measured in ft3
Calibrated against a volumetric standard within 6 months preceding VT
During VT, checked at least once, against reference meter
In-Line Meter. Serial # 1036707. Rockwell R-275. certified 1/18/99
Reference Meter model DTM 115 certified 9/22/98
Temperature Sensor/Thermometers: Initial Calibration Date: See Below
Calibrated against a certified temp, measurement standard within 6 months preceding VT
During VT, checked at least once, against an ASTM mercury-in-glass reference thermometer at
ambient temperature and be within 2%.
Temperature Indicator. Serial #40215. Model 402A. certified 1/7/99. certificate available but didn't
locate this indicator. Temp indicator in Lab. LN-560558. Model 400A. certified 1/7/99.
Oxygen Monitor: Initial Calibration Date:
Calibrated within the last six months
During VT, checked once every test day by sampling of ambient air
During operation of one combustion source, assessed for accuracy
Did not use as cited in a documented deviation report.
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Chemiluminescent Monitors to be used for Method 7E
Initial Interference Response conducted prior to VT Date: See Below
Measurement System Preparation prior to VT Date: See Below
Analyzer Calibration Error prior to VT Date: See Below
Sampling System Bias Check prior to VT Date: See Below
N02 to NO Conversion Efficiency Date: See Below
Calibrations Initial Calibration Date: See Below
4-point calibration with NO & N02 prior to VT, on each measurement range
For Horiba's VT both were run 1/20/99. however neither were done before first VT. Interference
response was conducted prior to Horiba's VT but not prior to the first VT.
Each point shall be prepared in triplicate - cited in a documented deviation report
Calibration error requirement: <±2% of span for the zero, midrange and high-range calibration
gases.
Zero and Span checks done daily AM and PM during the VT
Observed AM checks before source test, not present for PM.
Gas Dilution System Initial Calibration Date: 12/16/98
Flow measurement/control devices calibrated prior to VT by soap bubble flow meter.
Calibration Standards:
EPA Protocol 1 Gases (Calibration paperwork available):
NO in N2, High Range: 80-100% of span
Mid-Range: 40-60% of span
Zero: Concentration <0.25 % of span, ambient air
Protocol Cylinder # ALM057210 expiration date on certificate and cylinder tag did not match.
Cylinder # ALM017108 expiration date on certificate and cylinder tag did not match.
Certificate available for Cylinder # ALM036273 but could not locate cylinder.
Certificates for Source Lab cylinders (AAL14789. ALM014050. AAL17452. ALM015489N) could not
be initially located.
Sample Location:
Minimum of 8 duct diameters downstream and 2 duct diameters upstream of flow disturbances
and center point of the flue vent
The minimal distances from flow disturbances cited in the Reference Method relate to particulate and
are not critical for gases and were not used. Vendor's instrument sampling tubes were placed beside
those for the reference instruments.
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Day One - Laboratory Tests:
Linearity: (response over the full measuring range) - Not Observed
21 measurements for each analyte (NO, N02 or NOx)
Zero six times, each other three times
Calibration points used: 0, 10, 20, 40, 70 and 100% of the analyzer's measuring range
Horiba: 0-25, 0-50, 0-100, 0-250, 0-500, 0-1000, 0-2500
0, 250, 500, 1000, 1750 for 0-2500
Initial Zero and Span check?
After every three points, pure dilution gas provided and the analyzers' readings recorded?
Is the order of concentration points followed?
Final Zero and Span Check?
Linearity test was not observed; however, data sheets were examined. The 100% span used for the
Horiba was 500 ppm. The laboratory log sheets verified that 21 measurements were made, the order of
concentration points cited was used, and that initial and final Zero and Span checks were done.
Response Time Determinations - Not Observed
Analyzer's response recorded at 10 second intervals during Response Time check (estimated to be 30
readings)
Detection Limit - Not Observed
Detection limit is based on data from zero and 10% readings during Linearity test (9 readings)
Interrupted Sampling (four readings total) - Not Observed
Zero and Span recorded at end of Linearity Test on Day One
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Day Two - Laboratory Tests
Interrupted Sampling continued - Not Observed
Zero and Span are recorded after analyzer has been powered up before any adjustments
Same Span from previous day is used
Interference Tests: - Not Observed
Actual concentrations were obtained from the data sheets. A documented deviation cited the change in
the SOt and NO interferant concentrations.
Interferant
Interferant Concentration
Target Analyte
CO
500 ppm - Actual concentration used - 496 ppm
NO, N02, NOx
C02
5% - Actual percentage used - 5.03%
NO, N02, NOx
so2
500 ppm - Actual concentration used - 501 ppm
NO, N02, NOx
nh3
500 ppm - Actual concentration used - 494 ppm
NO, N02, NOx
Hydrocarbon Mixture
~ 500 ppm Cl3 -100 ppm C2, ~ 50 ppm C3 and C4
Hydrocarbon concentration used - 590 ppm
NO, N02, NOx
S02 and NO
250 ppm each - Actual concentration used -
451 ppm S02 & 393 ppm NO
NO, N02, NOx
Analyzer zeroed first and recorded
Interferant gas supplied, analyzer stabilized and analyte concentrations recorded (6 readings)
Flow Rate Sensitivity (9 readings) - Not Observed
Type of flow measuring device: automated bubble flowmeter, rotameter, or other
Ambient atmosphere and ambient flow rate recorded
Zero gas provided and recorded, span gas provided and recorded, zero provided again and recorded
Adjust pressure in system to +10" of water, record flow rate, repeat zero, span and zero
Adjust pressure in system to -10" of water, record, flow rate, repeat zero, span and zero
A leak was detected during the running of the flow rate test for the first vendor. The data sheets reflect
this and also indicate a correction factor would be used in the calculations. The correction factor was
based on the O^ value recorded on the vendor's monitors.
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Ambient Temperature (12 readings)
Room Temperature recorded (assumed to be above 45°F and below 105°F)
Zero and Span and Zero done at each temperature
Instrument allowed to equilibrate to chamber temperature for 1 hour
The ambient temperature test was observed. Room temperature readings were done first. Then the
monitors were placed in a heated chamber at 105°F at 13:24 and first readings were at 14:45. The
chamber door had to remain slightly aiar to keep the temperature constant. Next the monitors were
placed in the cooling chamber which was a household refrigerator. The heated monitors kept
overheating the refrigerator. After the initial hour to equilibrate the monitors, the refrigerator
temperature was at 110° F. To obtain the cooled ambient temperature needed for the test, the monitors
were placed out the laboratory window onto the adjacent roof for an hour and were brought to 47°F.
The cooling chamber test readings were taken from 6:38 pm to 6:43 pm.
This showed great ingenuity of the laboratory test staff to obtain the required ambient conditions for the
test.
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Day Three and Four - Source Tests
Method 7E
Measurement System Performance - Chemiluminescent Monitors
Thermo Environmental Instruments Model 10 and Model 14 A. Data were recorded off a voltage
meter attached to each instrument and voltage readings were then converted to concentrations.
The Fluke voltage meter attached to Model 14A was calibrated 11/2/98 and the one attached to
Model 10 was calibrated 11/3/98.
Zero Drift: <± 3% of the span over the period of each run
Calibration Drift: <± 3% of the span over the period of each run
Interference Check: <±7%
Measurement System Specifications:
A documented deviation cited changes to the sample probe and lines initially indicated to be allowed by
EPA Method CTM-022 but later revised per July 16. 1999 letter from Battelle indicating the changed
was based on Battelle's own experience with the sources used in the laboratory environment.
Sample Probe - Glass, stainless steel, or equivalent
Sample Line - Heated stainless steel or Teflon tubing
Sample Transport Lines - Stainless Steel or Teflon tubing
Calibration Valve Assembly - 3-way valve assembly or equivalent
Moisture Removal System - refrigerator-type condenser or similar device(?) - Ice Chest was used.
Particulate Filter - borosilicate or quartz glass wool or glass fiber mat, non-reactive with NOx,
in-stack or heated out-of-stack
Sample Pump - Leak free pump of any non-reactive material
Sample Flow Rate Control - control valve and rotameter or equivalent
Sample Gas Manifold - any non-reactive material
Data Recorder - strip chart recorder, analog computer or digital recorder;
resolution shall be 0.5% of span
A data recorder was not used. The test data was recorded on log sheets, one filled out by the
vendor on his monitors and one filled out by source laboratory operator for the reference
monitors. Calibrations prior to VT are recorded in a bound notebook. Entries are also made to
indicate the date and times the VTs in the source laboratory were run.
Sampling:
Measurements obtained only after twice the response time has elapsed
Zero and Calibration Drift tests performed immediately preceding and following every run
Adding zero gas & calibration gas (closely approximates the source) at calibration valve
Sampling continues only when zero and calibration drift are within specifications
Emission Calculations: - No calculations were observed
Concentrations are: avg readings (initial & final sampling system bias checks are averaged)
adjusted for the zero and upscale sampling system bias checks
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Relative Accuracy Tests
Low NOx Sources
Gas Cooktop: NO and N02 ranges 1-9 ppm
Must operate continuously during test (can't cycle off)
Must operate at steady-state (See Page 8 or 9)
Condition/Specification
Comments
Analyzers (two each) zeroed and span checked
initially only
/- Span was 20 ppm NO and 10 ppm N02
Sampling probes of analyzers placed beside
reference method probe
/- Lines to instruments are then connected into a
metal tube to top of stove top.
Analyzers are allowed to stabilize
/
After initial readings, probes are switched to
ambient air and stabilized
/
Sample Probes are returned to source for a total
of nine samplings
/
Final zero and span check conducted on analyzer
after each source, using the same span as initial
check
/
The cooktop used in the VT has been used by Battelle in a previous study. The data on the source
levels generated by the cooktop are documented in a Battelle report entitled "An Interlaboratory
Program to Validate a Protocol for the Measurement of MX Emissions from Rangetop Burners." The
data covers 1994 through 1998.
The gas supply for the cooktop is from a certified cylinder without sulfur.
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Water Heater: NO and N02 ranges 10-80 ppm
Must operate continuously during test (can't cycle off)
Must operate at steady-state (See Page 8 or 9)
Condition/Specification
Comments
Analyzers (two each) zeroed and span checked
initially only
/ - Span was 100 ppm NO and 15 ppm N02
Sampling probes of analyzers placed beside
reference method probe
/ - connect in a "T" together
Analyzers are allowed to stabilize
/
After initial readings, probes are switched to
ambient air and stabilized
/
Sample Probes are returned to source for a total
of nine samplings
/
Final zero and span check conducted on analyzer
after each source, using the same span as initial
check
/
The water heater used in the VT has been used by Battelle in a previous study. The data on the source
levels generated by the water heater is documented in a Battelle report entitled "An Interlaboratorv
Study to Determine the Precision of an Emission Measurement Protocol for Residential Gas Water
Heaters." The data covers 1994 through 1998.
The gas supply for the water heater was from the city gas supply. However. Battelle has a gas
chromatograph monitoring the concentration of the gas daily.
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Medium NOx Source
First Diesel Generator: NO and N02 ranges 100-1000 ppm NOx
Must operate at steady-state
Condition/Specification
Comments
Analyzers (two each) zeroed and span checked
initially only
/ - Generator was run at high RPM
Span was 200 ppm NO and 50 ppm N02
Sampling probes of analyzers placed beside
reference method probe
/
Analyzers are allowed to stabilize
/
After initial readings, probes are switched to
ambient air and stabilized
/
Sample Probes are returned to source for a total of
nine samplings
/- initial sampling observed only, auditors
departed
Analyzers are evaluated at three separate load
conditions per generator
Extended sampling interval (one hour) is
conducted during one load condition
See Note Below
Final zero and span check conducted on analyzer
after each source, using the same span as initial
check
Note: The Test/OA Plan called for two specific generators from the Air Force that were unavailable at
the time of the VT. A generator on-site was modified to be both the medium and high source. This
generator was run at a high RPM for the medium source and at idle for the high source. Because of the
noise level at the high RPM. most of the extended sampling interval (one hour) was done during the
high source test and not the medium source. One vendor chose to not submit its monitors to the high
source so its extended sampling interval was done during the medium source (high RPM).
Steady-State:
Temperature changes in the center position of the exhaust of not more than ±10°F;
NOx changes at the center of the exhaust duct of < ±5% relative to the mean over the 15 minute
interval as determined using the EPA reference method
02 changes, at the center of the exhaust duct of < ±0.50% absolute (±5000 ppm) from the mean
sampled over the 15 minute interval.
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High NOx Source - Not Observed
Second Diesel Generator: NO and N02 ranges 600-2300 ppm NOx
Must operate at steady-state
Condition/Specification
Comments
Analyzers (two each) zeroed and span checked
initially only
Sampling probes of analyzers placed beside
reference method probe
Analyzers are allowed to stabilize
After initial readings, probes are switched to
ambient air and stabilized
Sample Probes are returned to source for a total of
nine samplings
Analyzers are evaluated at three separate load
conditions per generator
Extended sampling interval (one hour) is
conducted during one load condition
Final zero and span check conducted on analyzer
after each source, using the same span as initial
check
Note: Instead of a second generator, the generator was run at idle to produce a span of 400 ppm NO
and 100 ppm MX.
Steady-State:
Temperature changes in the center position of the exhaust of not more than ±10°F;
NOx changes at the center of the exhaust duct of < ±5% relative to the mean over the 15 minute
interval as determined using the EPA reference method
02 changes, at the center of the exhaust duct of < ±0.50% absolute (±5000 ppm) from the mean
sampled over the 15 minute interval.
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