EPA-650/4-74-018
NOVEMBER 1974
Environmental Monitoring Series
j
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Research reports of the Office of Research and Development, Environmental
Protection Agency, have been grouped Into five series. These five broad
categories were established to facilitate further development and appli-
cation of environmental technology. Elimination of traditional grouping
was consciously planned to foster technology transfer and a maximum
interface in related fields. The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ENVIRONMENTAL MONITORING series.
This series describes research conducted to develop new or improved
methods and instrumentation for the identification and quantification
of environmental pollutants at the lowest conceivably significant concen-
trations. It also includes studies to determine the ambient concentrations
of pollutants in the environment and/or the variance of pollutants as a
function of time or meteorological factors.
Copies of this report are available free of charge to Federal employees,
current contractors and grantees, and nonprofit organizations - as
supplies permit - from the Air Pollution Technical Information Center,
Environmental Protection Agency, Research Triangle Park, North Carolina 27711;
or, for a fee, from-the National Technical Information Service, Springfield,
Virginia 22161.
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EPA-650/4-74-018
U.S. Envlronmente! Pretetten Agency
Rr 2bn III Information Resource
Center (3PM52)
811 Chesinut Street
PA 19107
GUIDELINES FOR DETERMINING PERFORMANCE
CHARACTERISTICS OF AUTOMATED METHODS
FOR MEASURING NITROGEN DIOXIDE
AND HYDROCARBONS CORRECTED
FOR METHANE IN AMBIENT AIR
by
Quality Assurance and Environmental
Monitoring Laboratory
National Environmental Research Center
Research Triangle Park, North Carolina
Program Element No. 1HA327
NATIONAL ENVIRONMENTAL RESEARCH CENTER
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
RESEARCH TRIANGLE PARK, NORTH CAROLINA 27711
November 1974
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This report has been reviewed by the Office of Research and Monitoring,
Environmental Protection Agency, and approved for publication. Approval
does not signify that the contents necessarily reflect the views and
policies of the Environmental Protection Agency, nor does mention of
trade names or commercial products constitute endorsement or recommenda-
tion for use.
Publication No. EPA-650/4-74-018
11
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CONTENTS
Page
LIST OF TABLES iv
LIST OF FIGURES iv
ABSTRACT ..... v
INTRODUCTION 1
1. Proposed Regulations for Determining
Equivalency 1
2. Nitrogen Dioxide 2
3. Hydrocarbons Corrected for Methane 3
4. Guidelines 4
TEST PROCEDURES FOR MEASURING PERFORMANCE
CHARACTERISTICS 7
1. General Provisions 7
2. Test Conditions 10
3. Generation of Test Atmospheres 12
4. Test Procedures 15
a. Range 15
b. Noise 15
c. Lower Detectable Limit 18
d. Interference Equivalent 20
e. Zero Drift, Span Drift, Lag Time, Rise Time,
Fall Time, and Precision 24
iii
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LIST OF. TABLES
Table 1. Performance Specifications 9
Table 2. Test Atmospheres 13''
Table 3. Interferent Test Concentration 21
Table 4. Line Voltage and Room Temperature Test Conditions . . 27
Table 5. Symbols and Abbreviations 40
LIST OF FIGURES
Figure 1. Form for Noise Data 17
Figure 2. Form for Data and Calculations for Lower
Detectable Limit and Interference Equivalent .... 19
Figure 3. Example of Typical Strip Chart Trace for the
Test Procedure for Drift, Lag Time, Rise Time,
Fall Time, and Precision 29
Figure 4. Form for Recording Data for Drift and Precision. . . 31
Figure 5. Form for Calculating for Zero Drift, Span Drift,
and Precision 35
Figure 6. Form for Summary of Test Results 39
IV
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ABSTRACT
Recommended performance specification and test procedures
are given for range, noise, lower detectable limit, interference
equivalent, zero drift, span drift, lag time, rise time, fall time,
and precision for automated methods for measuring nitrogen dioxide
and hydrocarbons corrected for methane.
These specifications and test procedures are intended for
use as guidelines to assist instrument manufacturers and instrument
users to determine performance characteristics for continuous air
monitoring analyzers.
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INTRODUCTION
1. PROPOSED REGULATIONS FOR DETERMINING EQUIVALENCY
Pursuant to Sections 109 and 301 of the 1970 Amendments to the Clean
Air Act (P.L. 91-604), the Administrator of the Environmental Protection
Agency (EPA) promulgated on April 30, 1971, National Primary and Secondary
Ambient Air Quality Standards for six air pollutants - sulfur dioxide,
participate matter, carbon monoxide, photochemical oxidants, hydrocarbons
corrected for methane, and nitrogen dioxide. This regulation included
a "reference method" for each of the six pollutants and stated that the
method, or an "equivalent method", must be used when conducting air
quality measurements to demonstrate achievement of the standards. An
equivalent method was defined as "any method of sampling and analyzing
for an air pollutant which can be demonstrated to the Administrator's
satisfaction to have a consistent relationship to the reference method."
The Administrator published on August 14, 1971, the Requirements for
Preparation, Adoption, and Submittal of Implementation Plans, which amended
the definition of an equivalent method to include the requirement that
2
certain performance specifications be met.
Regulations for the determination of equivalent and reference methods
for measuring sulfur dioxide, carbon monoxide, and photochemical oxidants
Code of Federal Regulations. Title 40 - Protection of Environment.
Part 50 - National Primary and Secondary Ambient Air Quality Standards.
Federal Register. 36_(84): 8186, April 30, 1976.
p
Code of Federal Regulations. Title 40 - Protection of Environment.
Section 51.17 - Air Quality Surveillance. Federal Register.
36_(158): 15492, August 14, 1971.
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were proposed on October 12, 1973. These regulations require
that the burden of proving equivalence of a method rests with the
requesting party, who must demonstrate that his method meets certain
performance specifications and produces air quality data having a
consistent relationship with data obtained by the reference method.
Interested persons have submitted written comments on the proposed
regulations, and, following consideration of the comments received,
the regulations have been revised and are being promulgated as a new
Part 53 entitled "Ambient Air Monitoring Equivalent and Reference
Method Requirements" to Title 40 of the Code of Federal Regulations.
Regulations for nitrogen dioxide and hydrocarbons corrected for methane
were not included in the new Part 53 because of technical problems
with the respective reference methods.
2. NITROGEN DIOXIDE
A reference method for nitrogen dioxide was set forth in Appendix F
Part 50 of Title 40 of the Code of Federal Regulations. On June 14, 1972,
however, EPA stated that the method was being re-evaluated. Results of
laboratory testing and air quality measurements made over a period of
several months at a large number of locations indicated several
A
deficiencies. On June 8, 1973, EPA announced its intention to amend
Part 50 of Title 40 of the Code of Federal Regulations by withdrawing
5
the original reference method for nitrogen dioxide. In addition,
3Federal Register. 38(197): 28438, October 12, 1973,
4Federal Register. 37_(H5): 11826, June 14, 1972.
5Federa1 Register. 38(110): 11574, June 8, 1973.
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EPA described three tentative methods being evaluated for possible
use as reference methods. Upon promulgation of a new reference method
for nitrogen dioxide, EPA will at the same time propose regulations for
the determination of equivalent or reference methods for nitrogen
dioxide.
3. HYDROCARBONS CORRECTED FOR METHANE
Section 51.14 of Title 40 of the Code of Federal Regulations
states that "it may be assumed that the degree of total hydrocarbon
emission reduction necessary for the attainment and maintenance of
national standard for photochemical oxidants will also be adequate for
the attainment of the national standards for hydrocarbons." EPA,
therefore, does not require the states to monitor hydrocarbons to
determine compliance with national ambient air standards. The reference
method for measuring hydrocarbons corrected for methane is a gas
chromatographic technique that measures total hydrocarbons, methane,
and carbon monoxide. Present commercially available instruments using
this technique are expensive, complex, and demand considerable operator
skill. They are marginal in their capability to measure hydrocarbons
corrected for methane on a routine unattended basis at or below levels
required by the national ambient air standard. Thus, because the states
are not required to monitor hydrocarbons and because there are problems
with the measurement methodology, EPA has not included hydrocarbons
corrected for methane in the proposed equivalency determination regulations
Code of Federal Regulations. Title 40 - Protection of Environment.
Section 51.14 Control Strategy. Federal Register. 36^(158): 15491,
August 14, 1971.
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4. GUIDELINES
Although EPA has not as yet proposed regulations for the determination
of equivalent and reference methods for nitrogen dioxide and hydrocarbons
corrected for methane, it has developed test procedures for measuring
performance characteristics as well as recommended performance
specifications for automated measurement methods for these pollutants.
These test procedures and performance specifications are provided in
this document and are intended as guidelines to help instrument
manufacturers design, build, test, and describe the operating characteristics
of their products. Instrument users will find the guidelines useful in
developing procurement specifications and acceptance tests, as well
as in enforcing warranties. In addition, the guidelines can assist
in testing existing instruments to determine their adequacy for air
quality measurements and in quality control auditing tests. Successful
passage of the test procedures for measuring performance characteristics
as described in these guidelines does not imply that the method tested
can be used as an equivalent or reference method, however.
When a new reference method is established for nitrogen dioxide,
EPA anticipates publishing regulations for the determination of equivalent
and reference methods similar to those proposed for sulfur dioxide,
carbon monoxide, and photochemical oxidants. The test procedures in
this document are presented in a format similar to that of existing
regulations in order to familiarize users of these guidelines with
procedures likely to become regulations once a new reference method
for nitrogen dioxide is designated. If regulations for equivalent
methods become necessary for hydrocarbons corrected for methane, EPA
4
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will likely produce corresponding regulations that will be similar
to the guidelines presented here.
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TEST PROCEDURES FOR MEASURING PERFORMANCE
CHARACTERISTICS
1. GENERAL PROVISIONS
(a) The test procedures given herein may be used to test the
performance of automated methods (i.e., analyzers) for measuring
nitrogen dioxide and hydrocarbons corrected for methane against
the minimum performance specifications given in Table 1 for each
performance parameter. To satisfy the requirements of these
guidelines, an analyzer must exhibit performance better than,
or equal to, the specified value for each and all specifications
listed.
(b) For each performance specification (except range), the test
procedure is to be initially repeated seven (7) times, to yield
seven (7) test results. Each result is to be compared with the
corresponding specification in Table 1; a value higher or outside
that specified constitutes a failure. These seven results for each
parameter are then interpreted as follows:
(1) Zero (0) failures: analyzer passes the performance
parameter.
(2) Three (3) or more failures: analyzer fails the
performance parameter.
(3) One (1) or two (2) failures: repeat the test
procedure for the parameter eight (8) additional times yielding
a total of fifteen (15) test results. The combined total of
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fifteen test results is interpreted as follows:
(i) One (1) or two (2) failures: analyzer passes the
performance parameter.
(ii) Three (3) or more failures: analyzer fails the
performance parameter.
(c) During conduct of these tests, the analyzer should be operated
in the range specified in Table 1, or in any lower (more sensitive)
range. The actual range used in the test should be clearly indicated.
An analyzer may be operated in a higher (less sensitive) range if
sufficient justification for such operation exists. For an analyzer
capable of operation in two or more ranges (multiple range capability),
appropriate test data should be obtained for each range available, and
the analyzer must pass all performance specifications for each range to
satisfy the requirements of this guideline.
(d) The tests for zero drift, span drift, lag time, fall time,
rise time, and precision are combined into a single procedure which is
conducted at various voltages and various ambient temperatures. The
tests for noise, lower detectable limit, and interference equivalent
are made at any temperature between 20°C and 30°C and at any normal
line voltage between 105 and 125 volts, and are to be conducted such
that not more than three (3) test results for each parameter are obtained
per 24 hours.
(e) All analyzer response readings to be recorded should first be
converted to concentration units according to the calibration curve.
(f) All recorder chart tracings, records, test data, and other documentation
obtained from or pertinent to these tests should be identified, dated, and
8
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Table 1. PERFORMANCE SPECIFICATIONS'
Performance parameter
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Range
Noise
Lower detectable limit
Interference equivalent:
Each interferent
Total interferent
Zero drift, 12- and 24-hour
Span drift, 24-hour
Lag time
Rise time, 95%
Fall time, 95%
Precision:
20% of upper range limit
80% of upper range limit
Unitsb
ppm
ppm
ppm
ppm
ppm
ppm
percent
minutes
minutes
minutes
Ppm
ppm
N02
0-0.5
0.005
0.01
+0.02
"0.04
+0.02
±5
20
15
15
0.02
0.03
Hydrocarbons corrected
for methanec>d
0-5
0.05
0.1
+0.1
"0.2
+0.2
+5
10
10
10
0.3
0.3
aAll performance specifications are subject to revaluation at any time and may be subject to change if
sufficient justification exists.
bTo convert from ppm to yg/m3 at 25°C and 760mm Hg, multiply by M.W./O.02447, where M.W. is the molecular
weight of the gas.
cFor analyzers that read only "total hydrocarbons" and "methane" separately, readings for hydrocarbons
corrected for methane are derived as the total hydrocarbon reading minus the concurrent methane reading.
Determine as methane or as methane equivalent: 1.0 ppm ethane = 2.0 ppm methane equivalent.
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signed by the analyst performing the test. Suggested formats for
reporting the test results and calculations are provided in Figures 1,
2, 4, 5, and 6.
2. TEST CONDITIONS
(a) Set-up and start-up of the analyzer shall be in strict accordance
with the analyzer's operating instructions. (Allow adequate warm-up or
stabilization time as indicated in the operating instructions before
beginning the tests.) If the analyzer does not have an integral strip
chart recorder, connect the analyzer output to a suitable strip chart
recorder of the servo, null-balance type. This recorder should have a
chart width of at least 25 centimeters, chart speeds up to 10 centimeters
per hour, a response time of 1 second or less, a deadband of not more than
0.25 percent of full scale, and capability of either reading measurements
at least 5 percent below zero or offsetting the zero by at least 5 percent.
(b) Calibration of the analyzer should be as indicated by the
analyzer's operating instructions and as follows: If the chart recorder
does not have below-zero capability, adjust either the analyzer's
controls or the chart recorder to obtain a +5 percent offset-zero
reading on the recorder chart to facilitate observing negative response
or drift. If the analyzer is not capable of negative response, the
analyzer (not recorder) must be operated with an offset zero. Construct
a calibration curve by plotting recorder scale readings (ordinate)
against pollutant concentrations (abscissa). A plot of analyzer
output units (volts, millivolts, mi 11 lamps, etc.) against
pollutant concentration should also be shown for analyzers not
having an integral chart recorder. All such plots should consist of at
10
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least seven (7) approximately equally spaced, identifiable points
including 0 and 90 + 5 percent of full scale. Calibration of analyzers
for hydrocarbons corrected for methane should be based on either
methane or methane equivalent. Methane may be used to calibrate
"total hydrocarbon" or "methane" scales, but analyzers that read
hydrocarbons corrected for methane directly should be calibrated with
ethane, as methane equivalent. One ppm ethane is equivalent to 2 ppm
methane.
(c) It is intended that analyzers be capable of unattended operation for
at least three (3) days. Therefore, once the analyzer has been set-up
and calibrated and the tests have started, manual adjustments or normal
periodic maintenance on the analyzer is permitted only every three days.
Automatic adjustments that the analyzer performs by itself are permitted
at any time. Thus, the tests are to be carried out in a series of 3-day
periods during which no manual adjustments are permitted. The strip chart
records should clearly show when manual adjustments or periodic maintenance
was made and describe the operations performed.
(d) If the analyzer should malfunction during any of the performance
tests, the tests for that parameter should be re-initiated. A detailed
explanation of the malfunction, remedial action taken, and whether
recalibration was necessary (along with all pertinent records and
charts) should be prepared. If more than one malfunction occurs, all
performance test procedures for all parameters should be repeated.
(e) Normal analyzer operation or malfunction should not generate
or present any hazards or hazardous conditions to operators or to the
environment. Analyzers should include necessary safety devices to
prevent such hazards and to prevent damage to the internal components
11
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of the analyzer. Operation manuals should adequately warn of possible
safety hazards and describe any necessary safety precautions.
(f) Tests for all performance parameters are to be completed on
the same analyzer; use of multiple analyzers to accelerate testing is
permitted only when testing alternate ranges of a multi-range analyzer.
3. GENERATION OF TEST ATMOSPHERES
(a) Table 2 gives preferred methods for generating test atmospheres
as well as suggested methods of verifying the concentrations. Only
one means of establishing the concentration of a test atmosphere is
normally required. If the method of generation can produce accurate
concentrations, verification is optional. If the method of generation
is not accurate, then establishment of the concentration by some
verification method is required.
(b) The test atmosphere delivery system should be designed and
constructed so as not to significantly alter the test atmosphere
composition or concentration during the period of the test. The
delivery system should be fabricated from borosilicate glass or FEP
Teflon.
(c) The output of the test atmosphere generation system must be
sufficiently stable to obtain stable analyzer response during the
required tests. If a permeation device is used for generation of a
test atmosphere, the device, as well as the air passing over it, must
be controlled to +0.1°C.
(d) All diluent air should be zero air free of contaminants likely
to cause a detectable response on the analyzer.
(e) The concentration of each test atmosphere should be established
or verified before or during each series of tests. Samples for verifying
12
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Table 2. TEST ATMOSPHERES
Test gas
Generation
Verification
Ammonia
Carbon monoxide
Ethane
Methane
Nitric oxide
Nitrogen dioxide
Ozone
Sulfur dioxide
Water
Permeation device. Similar to system described
in References 1 and 2.
Cylinder of zero air or nitrogen containing CO1
as required to obtain the concentration
specified in Table 3.
Cylinder of zero air or nitrogen containing ,
ethane as required to obtain the concentra-
tion specified in Table 3.
Cylinder of zero air containing methane as
required to obtain the concentration
specified in Table 3. *
Cylinder3 of "prepurified" nitrogen containing
approximately 100 ppm NO. Dilute with zero
air to concentration specified in Table 1.
1. Gas phase titration
Reference 4.
as described in
2. Permeation device, similar to system
described in References 1 and 2.
Calibrated ozone generator as described in
Reference 5, Appendix D.
Permeation device. Similar to system described
in reference method for 502 » Reference 5,
Appendix A.
Pass zero air through distilled water at a
fixed known temperature between 20° to 30°C
such that the air stream becomes saturated.
Dilute with zero air to concentration
specified in Table 3.
Indolphenol method, Reference 3.
Use National Bureau of Standard (NBS)-
certified standards whenever possible.
If NBS standards are not available,
obtain 2 standards, from independent
sources, which agree within 2 percent,
or obtain one standard and submit it to
an independent laboratory for analysis,
which must agree within 2 percent of
the supplier's nominal analysis.
Gas phase titration as described in
Reference 4, Section 7.1.
1. Use an N02 analyzer calibrated with
a gravimetrically calibrated permeation
device.
2. Use an NOg analyzer calibrated by
gas phase titration as described in
Reference 4.
Use an ozone analyzer calibrated by gas
phase titration as described in Refer-
ence 4.
P-rosaniline method. Reference 5, Appen-
Appendix A.
Measure relative humidity by means of a
dew point indicator, calibrated electro-
lytic or piezoelectric hygrometer or
or wet/dry bulb thermometer.
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Table 2 (continued). TEST ATMOSPHERES
Test gas Generation Verification
Zero air 1. Ambient air purified by appropriate scrubbers
or other devices sucK that it is free of contam-
inants likely to cause a detectable response on
the analyzer.
2. Cylinder of compressed zero air certified by
the supplier or an independent laboratory to be
free of contaminants likely to cause a detect-
able response on the analyzer.
aL)se stainless steel pressure regulator dedicated to the pollutant measured.
Ref. 1 - O'Keeffe, A.E., and G.C. Ortman. Primary Standards for Trace Gas Analysis. Anal. Chem. 38;
760, 1966.
Ref. 2 - Scaringelli, P.P., A.E. O'Keeffe, E. Rosenberg, and J.P. Bell. Preparation of Known
Concentrations of Gases and Vapors With Permeation Devices Calibrated Gravimetrically. Anal.
Chem. 42:871, 1970.
Ref. 3 - Tentative Method of Analysis for Ammonia in the Atmosphere (Indolphenol Method). Health Lab.
Sciences. 10. (2): 115-118, April 1973.
Ref. 4 - Tentative Method for the Continuous Measurement of Nitrogen Dioxide (Chemiluminescent),
Addenda C. Federal Register. 38J110): 28438, October 12, 1973.
Ref. 5 - National Primary and Secondary Ambient Air Quality Standards. Federal Register. 36_(84):8186,
April 30, 1971.
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test concentrations should be collected from the test atmosphere
delivery system as close as possible to the sample intake port of the
analyzer under test.
(f) The accuracy of all flow measurements used to calculate test
atmosphere concentrations should be documented and referenced to a
primary standard. All flow measurements given in volume units should
be standardized to 25°C and 760 mm Hg.
(g) Schematic drawings and other information showing complete
procedural details of the test gas generation, verification, and
delivery system should be included in the test results. All pertinent
calculations should also be clearly indicated.
TEST PROCEDURES
(a) Range
(1) Technical Definition: Nominal minimum and maximum
concentrations which the analyzer shall be capable of measuring.
The nominal range is specified at the lower and upper range
limits in concentration units, for example: 0-0.5 ppm.
(2) Test Procedure: This test is satisfied by a suitable
calibration curve, as specified in Section 2 (b), showing
analyzer response over the required range.
(b) Noise
(1) Technical Definition: Spontaneous, short duration
deviations in the analyzer output, about the mean output,
which are not caused by input concentration changes. Noise is
determined as the standard deviation about the mean and expressed
in concentration units.
15
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(2) Test Procedure:
(i) Allow sufficient time for the analyzer to
warm up and stabilize. Noise is determined at two
concentrations using zero air and then a pollutant test
gas concentration as indicated below. The noise
specification in Table 1 applies to both of these tests.
(ii) Connect an integrating type digital meter (DM)
suitable for the analyzer output and accurate to three
significant digits, to measure the analyzer's output
signal. Use of a chart recorder in addition to the
DM is optional.
(iii) Measure zero air for 60 minutes. During this
60-minute interval, record twenty-five (25) DM readings
at 2-minute intervals (Figure 1).
(iv) Convert each DM reading to concentration units
by reference to the analyzer calibration curve
as determined in Section 2 (b).. Label the converted
DM readings r-j, rg» r^ rgg.
(v) Calculate the standard deviation, S, as follows:
25
- 1/25 (irj2
& (ppn)
24
where 4. indicates the i-th DM reading in parts per million.
(vi) Let S at 0 ppm be identified as SQ; compare
SQ to the noise specification given in Table 1.
16
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Applicant
Test No _
Analyzer .
READING
NUMBER
(i)
Date.
Range.
TIME
0% of URL
DM
READING
r., ppm
80% of URL
DM
READING
r,,ppm
1
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
25
Er,
25
£r,2
S0 =
S80 =
Figure 1. Form for noise data.
17
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(vii) Repeat steps (111) through (vi) using a pollutant
test atmosphere concentration of 80 percent ± 5 percent of
the upper range limit (URL) instead of zero gas, and let S at
80 percent of the URL be identified as SQQ. Compare SgQ to
the noise specification given in Table 1.
(viii) Both SQ and SQO must be less than or equal to the
specification for noise to pass this test.
(c) Lower Detectable Limit
(1) Technical Definition: The minimum pollutant concentration
that produces a signal of twice the noise level.
(2) Test Procedure:
(i) Allow sufficient time for the analyzer to warm up
and stabilize. Measure zero air and record the stable
reading as B, (Figure 2).
(ii) Generate and measure a pollutant test atmosphere
concentration equal to the value for lower detectable
limit specified in Table 1. The test atmosphere
concentration may be generated or verified at a higher
concentration, then accurately diluted with zero air to
the final required concentration.
(iii) Record the analyzer's stable indicated reading
in ppm, as B. .
(iv) Determine the lower detectable limit (LDL) as
LDL = BL - By. Compare this LDL value with the noise
level, S/j, determined in Section 4 (b), for 0 concentration
test atmosphere. LDL must be equal to or higher than
18
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Applicant.
Analyzei _
Range
TEST
PARAMETER
LOWER
DETECTABLE
LIMIT
1 INTERFERENCE
EQUIVALENT
1
2
3
4
5
TOTAL
READING OR
CALCULATION
BZ
BL
LDL=BL-
Bz
RI
RM
1C* — D D
R,
RI>
IEo = Rj2 - R.2
R3
R13
IE3 =R,3 - R3
R4
R.4
IE4 = RI4 -
R4
Ra
RI5
»E» = Ri5-Ro
IET-&E,
1=1
TEST NUMBER
1
2
3
4
5
6
7
8
9
10
11
12
13
14
IS
Figure 2. Form for data and calculations for lower detectable limit and interference equivalent.
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2 times SQ to pass this test.
(d) Interference Equivalent
(1) Technical Definition: Positive or negative response
caused by a substance other than the one being measured.
(2) Test Procedure: The analyzer is to be tested for all
substances likely to cause a detectable response. The analyzer
is challenged, in turn, with each interfering agent specified
in Table 3. In the event that there are substances likely to
cause a significant interference that have not been specified
in Table 3, these substances shall be tested at a concentration
substantially higher than that normally found in the ambient air.
The interference may be either positive or negative, depending
on whether the analyzer's response is increased or decreased
by the presence of the interferent. Interference equivalents
are determined by mixing each interferent, one at a time, with
the pollutant at the concentrations specified in Table 3, and
comparing the analyzer's response to the response caused by the
pollutant alone. Known gas-phase reactions that might occur
between an interferent and the pollutant are designated by
footnote c in Table 3. In these cases, the interference
equivalent should be determined in the absence of the pollutant.
(i) Allow sufficient time for warm-up and stabilization
of the analyzer.
(ii) For analyzers using a prefilter or scrubber based
upon a chemical reaction to derive part of its specificity
and requiring periodic service or maintenance, the
analyzer shall be "conditioned" prior to each inter-
20
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Table 3. INTERFERENT TEST CONCENTRATION
(parts per million)
Pollutant and.
analyzer type
Ammonia
Interferents3
Sulfur
Dioxide
Nitric
Oxide
Ozone
Water
Vapor
Carbon
Monoxide
Methane
Nitrogen Dioxide, 0.1
Chemi luminescent
Spectrophotometri c-
wet chemical (azo-
dye reaction)
Electrochemical
Spectrophotometri c-
gas phase
O.ic
O.lc
O.ic
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
20,000
20,000C
20,000C
50
50
PO
NMHCet 2.0 ppm ethane^
Flame ionization
detector
20,000
50
4.0
Concentrations of interferent listed must be prepared and controlled to -10 percent of stated value.
Analyzer types not listed should be challenged with appropriate concentrations of substances likely to
cause an interference.
°Do not mix with pollutant.
Concentration of pollutant used for test. These pollutant concentrations must be prepared to -10 percent
of stated value.
eHydrocarbons corrected for methane.
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ference test as follows:
(a) Service or perform the indicated maintenance on
the scrubber or prefliter as directed in the analyzer's
operating instructions.
(b) Before testing for each interferent, allow the
analyzer to sample through the scrubber a test
atmosphere containing the interferent at a concentration
equal to the value specified in Table 3. Sampling
shall be at the normal flowrate and shall be continued
for six (6) continuous hours prior to testing.
(ill) Generate three (3) test atmosphere streams as follows:
(a) Test atmosphere P; Pollutant concentration.
(b) Test atmosphere I: Interferent concentration.
(c) Test atmosphere Z: Zero air.
(iv) Adjust the individual flow rates and the pollutant or
interferent generators for the three test atmospheres as
follows:
(a) The flowrates of test atmospheres I and Z shall
be identical.
(b) The concentration of pollutant in test
atmosphere P shall be adjusted such that when P is
mixed (diluted) with either test atmosphere I or Z,
the resulting concentration of pollutant shall be as
specified in Table 3.
(c) The concentration of interferent in test
atmosphere I shall be adjusted such that when I is
mixed (diluted) with test atmosphere P, the resulting
22
-------
concentration of interferent shall be equal to the
value specified in Table 3.
(d) To minimize concentration errors caused by
flow rate differences between I and Z, it is recommended
that the flow rate of P be from 10 to 20 times larger
than the flowrates of I and Z.
(v) Mix test atmosphere P and Z by passing the total flow
of both atmospheres through a mixing flask.
(vi) Measure the mixture of test atmospheres P and Z.
Allow for a stable reading, and record the reading, in
concentration units, as R (Figure 2).
(vii) Mix test atmospheres P and I by passing the total flow
of both atmospheres through a mixing flask.
(viii) Measure this mixture and allow for a stable reading.
Record the reading, in concentration units, as Rr.
(ix) Calculate the interference equivalent as:
IE = Rr - R
IE must be equal to or less than the specification given in
Table 1 for each interferent to pass the test.
(x) Follow steps (iii) through (ix), in turn, to determine
the interference equivalent for each interferent.
(xi) For those interferents which cannot be mixed with the
pollutant, as indicated by footnote c in Table 3, adjust
the concentration of the interferent in test atmosphere I
to the specified value without mixing with the pollutant
test atmosphere. Determine IE as follows:
(a) Sample and measure test atmosphere Z (zero air).
23
-------
Allow for a stable reading and record the reading,
in concentration units, as R.
(b) Sample and measure the interferent test
atmosphere I. If the analyzer is not capable of
negative readings, be sure the analyzer (.not the
recorder) is adjusted to give an offset zero. Record
the stable reading in concentration units as RT,
extrapolating the calibration curve, if necessary,
to represent negative readings.
(c) Calculate IE = Rj - R. IE must be equal to or
less than the specification in Table 1 to pass the
test.
Cxii) Sum the absolute value of all the individual inter-
ference equivalents. This sum must be equal to or less
than the total interferent specification given in Table 1
to pass the test. (NOTE: Specifications for interferent
equivalents are not intended to indicate the allowable
measurement inaccuracy at the levels of the air quality
standards. The interferent equivalent specifications are
predicated on challenging the candidate analyzer with a
maximal concentration of potential interferents.)
(e) Zero Drift. Span Drift. Lag Time, Rise Time, Fall Time,
and Precision
(1) Technical Definitions;
(i) Zero Drift: The change in analyzer response to zero
pollutant concentration, over 12- and 24-hour periods of
continuous unadjusted operation.
24
-------
(ii) Span Drift: The percentage change in analyzer
response to an up-scale pollutant concentration over
a 24-hour period of continuous unadjusted operation.
(iii) Lag Time: The time interval between a step
change in input concentration at the analyzer inlet, and
the first observable corresponding change in the analyzer
response.
(iv) Rise Time: The time interval between initial
response and 95 percent of final response after a step
increase in input concentration.
(v) Fall Time: The time interval between initial
response and 95 percent of final response after a step
decrease in input concentration.
(vi) Precision: Variation about the mean of repeated
measurements of the same pollutant concentration,
expressed as one standard deviation about the mean.
(2) Tests for these performance parameters are to be
accomplished over a period of seven (7) or more days. During
this time, the line voltage supplied to the candidate analyzer
and the ambient temperature surrounding the analyzer are
varied from day to day. One test result for each performance
parameter is obtained each test day for either seven (7)
or fifteen (15) test days as necessary. If work schedules,
slow analyzer response, or other factors prohibit completion of
the entire test procedure in the available time each day,
the tests may be divided and conducted separately in two 7-
or 15-day test periods as necessary.
25
-------
(3) During any test period, periodic maintenance and manual
adjustments to the electronics or to the gas or reagent flows
are permitted only once every three (3) days. Automatic
adjustments that the analyzer performs by itself are permitted
at any time. Any interruptions will require repeating the 3-day
test period during which the interruption occurred.
(4) This test shall be conducted either in an uninterrupted
period of seven (7) to fifteen (15) days, or in increments of
three (3) consecutive days. For example, if the test is
interrupted by weekends, it may be performed in 3-day increments
where adjustments are made on Monday and readings are taken on
Tuesday, Wednesday, and Thursday.
(5) The 24-hour test day may begin at any clock hour. The
first 12 hours out of each test day are required for
testing 12-hour zero drift. Tests for the other parameters
are conducted during the remaining 12 hours.
(6) Table 4 gives the line voltage and room temperature
to be used for each test day. The line voltage and temperature
are to be changed to the specified values at the start of
each test day (i.e., at the start of the 12-hour zero test).
Initial adjustments (day zero) are made at a line voltage of
115 volts (rms) and a room temperature of 25°C.
(7) Every three (3) days the analyzer may be adjusted and/or
serviced according to the periodic maintenance procedures speci-
fied in the analyzer's operations manual. This must be done
immediately after completion of the day's tests, at the voltage
and temperature specified for that day, and only on test days
26
-------
Table 4. LINE VOLTAGE AND ROOM TEMPERATURE TEST CONDITIONS
Test
day
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
rms
Line
vol tage
115
125
105
125
105
125
105
125
105
125
105
125
105
125
105
125
Room
temperature, °Cb
25
20
20
30
30
20
20
30
30
20
20
30
30
20
20
30
Comment
Initial set-up and adjustments,
Adjustments and/or periodic
maintenance permitted at end of tests.
Adjustments and/or periodic
maintenance permitted at end of tests.
Examine test results to ascertain
if further testing is required.
Adjustments and/or periodic
maintenance permitted at end of tests.
Adjustments and/or periodic
maintenance permitted at end of tests.
Voltage specified shall be controlled to +1 volt.
Temperature specified shall be controlled to +1°C.
27
-------
3, 6, 9, and 12. If necessary, the beginning of the test days
succeeding such service or adjustment may be delayed as
necessary to complete the service or adjustment operation.
(8) All analyzer response readings to be recorded should
first be converted to concentration units according to the
calibration curve. Whenever a test atmosphere is to be measured,
but a stable reading is not required, the test atmosphere need
be measured only long enough to cause a change in analyzer
response of at least 10 percent of full scale. Identify all readings
and other pertinent data on the strip chart. Figure 3
illustrates the pattern of the required readings.
(9) Test Procedure
(i) Arrange to generate pollutant test atmospheres
as follows:
Test Atmosphere Pollutant Concentration
AQ Zero gas
A2Q 20 ± 5% of upper range limit
A— 30 - 5% of upper range limit
80 | 5% of upper range limit
90 - 5% of upper range limit
Test atmospheres AQ, A«Q and AfiQ must be consistent
during the tests and from day to day.
(ii) For steps (xxv) through (xxxi), a chart speed of at
least 10 centimeters per hour should be used. The actual
chart speed, chart speed changes, and time checks should
be clearly marked on the chart.
(iii) Allow sufficient time for analyzer to warm up and
stabilize at a line voltage of 115 volts and a room
28
-------
(% SCALE WITH 5% OFFSET ZERO)
1 LAG '
1 TIME I
RISE o.95 Pg
_ . MARK FOR
0 \ LAG TIME
I
O
CHART SPEED=_cm/min:
STABLE
READINGS
NOT REQUIRED
Figure 3. Example of a typical strip chart trace for the test procedure
for drift, lag time, rise time, fall time, and precision.
29
-------
temperature of 25°C. Recalibrate, if necessary, and
adjust the zero baseline to 5 percent of chart. No further
adjustments shall be made to the analyzer until the end
of the tests on the third day.
(iv) Measure test atmosphere AQ until a stable analyzer
reading is obtained, and record this reading (in ppm)
as Z', where n = 0 (Figure 4).
(v) Measure test atmosphere A2Q. Allow for a stable
reading and record it as M', where n = 0.
(vi) Measure a test atmosphere Ago. Allow for a stable
reading and record it as S", where n = 0.
n
(vii) The above readings for Z', M', and S', should
be taken at least seven (7) hours prior to beginning
of test day 1.
(viii) At the beginning of each test day, adjust the
line voltage and room temperature to the values given
in Table 4.
(ix) Measure test atmosphere A continuously for at
least twelve (12) consecutive hours during each test day.
(x) At the end of the 12-hour zero drift test (step ix),
sample test atmosphere A0 until the analyzer reading
is below 15 percent of full scale. A stable reading is not
required.
(xi) Measure test atmosphere A«Q and record the stable
reading (in ppm) as P, (Figure 4).
(xii) Sample test atmosphere A3Q; a stable reading is
not required.
(xiii) Measure test atmosphere Apn and record the stable
reading as ?2.
30
-------
Applicant
Analyzer.
.Range
TEST DAY (n)
ANALYZER READING, ppm
1 2
7
8
10 11 12 13 14
15
DATE
P4
PS
6
£ p,2
1=1
PIO
PII
Pl2
12
i=7
max
Figure 4. Form for recording data for drift and precision,
-------
(xiv) Sample test atmosphere AO; a stable reading is
not required.
(xv) Measure test atmosphere A20 and record the stable
reading as P3.
(xvi) Sample test atmosphere A^Q; a stable reading is
not required.
(xvii) Measure test atmosphere A2Q and record the stable
reading as P«.
(xviii) Sample test atmosphere Afl; a stable reading is
not required.
(xix) Measure test atmosphere A2Q and record the stable
reading as P,..
(xx) Sample test atmosphere A3Q; a stable reading is
not required.
(xxi) Measure test atmosphere A20 and record the stable
reading as Pg
(xxii) Measure test atmosphere AgQ and record the stable
reading as Pj.
(xxiii) Sample test atmosphere Ago; a stable reading is
not required.
(xxiv) Measure test atmosphere AQQ and record the stable
reading as Pg. Increase chart speed to at least 10
centimeters per hour.
(xxv) Measure test atmosphere A0. Record the stable
reading as L..
32
-------
(xxvi) Quickly switch the analyzer to measure test
atmosphere AgQ and mark the recorder chart to show
the exact time when the switch occurred.
(xxvii) Measure test atmosphere Ago and record the stable
reading as P .
(xxviii) Sample test atmosphere AgQ; a stable reading is
not required.
(xxix) Measure test atmosphere AgQ and record the
stable reading as P-JQ.
(xxx) Measure test atmosphere AQ and record the stable
reading as L£.
Cxxxi) Measure test atmosphere AQQ and record the stable
reading as P^.
(xxxii) Sample test atmosphere AgQ; a stable reading
is not required.
(xxxiii) Measure test atmosphere Afin and record the stable
reading as P^-
(xxxiv) Repeat steps (viii) to (xxxiii) each test day.
(xxxv) If zero and span adjustments are made after the
readings are taken on test days 3, 6, 9, or 12,
complete all adjustments; then measure test atmospheres
A , AgQ, and AgQ. Allow for a stable reading on each
and record the readings as Z^, S^, and M^,respectively,
where n = the test day number.
33
-------
(10) Determine the results of each day's tests as follows.
Mark the recorder chart to show readings and determinations.
(i) Zero Drift:
(a) 12-hour. Examine the strip chart pertaining
to the 12-hour continuous zero gas test.
Determine the minimum (C . ) and maximum (Cmax)
readings (in ppm) during this period of 12
consecutive hours, extrapolating the calibration
curve to negative concentration units if
necessary. Determine the 12-hour zero drift
(12ZD)asl2ZD = Cmax-Cm.n(Figure5).
(b) Calculate the 24-hour zero drift (24ZD) for
the n-tk test day as 24ZD = Z - Z _j, or
24ZD^ = Z - Z'_, if zero adjustment was on
the previous day, where Z^ = L| + L2 for LI and L2
2
taken on the n-th test day.
(c) Compare 12ZD and 24ZD to the zero drift
specification in Table 1. Both 12ZD and 24ZD
must be equal to or less than the specified
value to pass the test for zero drift.
34
-------
Applicant
Analyzer
Range
TEST
PARAMETER
Zero
drift
Span
drift
Precision
12
hour
24
hour
20".
URL
80%
URL
20%
URL
80%
URL
CALCULATION
'-'ZD'Cnuv-C,,,,,,
ZS'XL^LO
^ZD^Z^Z,,.,
24ZDn=Zn-Z;,.,
".-*£ p,
M-Mn .
MSD - l x 100°'
Mn-l
Mn~Mn-l
Men - n Y inn0^
Mn_i
12
S"-T^P'
6 i =7
Sn - Sn.i
u'in - •— -- x mo07
^n-l
s — s '
iicr\ _ ,.n. "~\ Y mn?7
5n-l
P^^8i')l
p°°-ffit-X?/.)]
n - th TEST DAY
1
^
p
s/^'
^
^
2
^?
i
1
3
^
1
i
4
S
^
i
i
6
^
i
l
7
8
^
1
i
9
^
i
i
10
r
11
=^
i
i
12
^
i
i
13
14
'*&
%
i
'%
15
3%
i
i
CO
01
Figure 5. Form for calculating zero drift, span drift, and precision.
-------
tii) Span Drift
(a) Span drift at 20% of URL (MSD):
- M i
flSDw = n ' X 100 %, or
Mn-J
MSDW = ~ X 100
" -
if span adjustment was made on the previous
day, where
6 1 = 1 '
n indicates the n-tk test day, and -t
indicates the 4,-tk reading on the n-tk
test day.
Cb) Span drift at 80% of URL (USD):
USDW « n n'J X 100 %, or
n" n~1 X 100
if span adjustment was made on the previous
day, where
--- 12 _
,
6 , -7 t
n indicates the n-th test day, and
36
-------
JL indicates the i-th reading on the
n-tin. test day.
(c) Both USD and MSD must be equal to or less than
the specification given in Table 1 to pass
the test for span drift.
(iii) Lag Time; Determine, from the strip chart, the
elapsed time in minutes between the mark made in
step (xxvi) and the first observable (two times the
noise level) analyzer response. This time must be
equal to or less than the time specified in Table 1
to pass the test for lag time.
(iv) Rise Time; Calculate 95 percent of reading Pg and
determine, from the recorder chart, the elapsed time
*
between the first observable (two times noise level)
analyzer response and a response equal to 95 percent
of the Pg reading. This time must be equal to or less than
the rise time specified in Table 1 to pass the test
for rise time.
(v) Fall Time: Calculate 95 percent of (PIQ - l_2) and
determine, from the strip chart, the elapsed time in
minutes between the first observable decrease in
analyzer response following reading P,Q and a response
equal to 95 percent of (P,Q - Lg). This time must be
equal to or less than the fall time specification
in Table 1 to pass the test for fall time.
37
-------
(vi) Precision. Calculate precision for each day's
test as follows:
Cb} P
-MMJW]
Cc) Both. P. and P must be equal to or less
20 80
than the specification given in Table 1 to
pass the test for precision.
38
-------
Applicant
Analyzer.
Analysts.
Range.
PERFORMANCE
PARAMETER
NOISE.
ppm
0°. URL (S0)
80'. URL (S80)
LDL must be 2 x noise")
INTER-
FERENCE
EQUIV-
ALENT.
ppm
ZERO
DRIFT,
ppm
SPAN
DRIFT.
".
'El
IE2
'E3
IE4
'E5
TOTAL (IET)
12 hour (12ZO)
24 hour (24ZD)
20% URL (MSD)
80% URL (USD)
LAG TIME, mm
RISE TIME, mm
FALL TIME, mm
PRECISION, 20% URL (P2Q)
ppm
80% URL (P80)
Table
B-l
spec.
m
TEST
1
2
3
4
5
6
7
TEST
8
9
10
11
12
13
14
15
No. of
test
failures
Pass
or
fail
CO
to
aCompare each test LDL reading with the corresponding noise measurements. LDL reading must exceed the 0% URL noise value by
a factor of 2 to pass the test for LDL
Figure 6. Form for summary of test results.
-------
Table 5. SYMBOLS AND ABBREVIATIONS
B|_ Analyzer reading at specified LDL concentration
BZ Analyzer reading at 0 concentration for LDL test
DM Digital meter
Cmax Maximum analyzer reading during 12ZD test
Cmi-n Minimum analyzer reading during 12ZD test
•i Subscript indicating the JL-th quantity in a series
IE Interference equivalent
LI First analyzer zero reading for 24ZD test
L2 Second analyzer zero reading for 24ZD test
MK Average of PI...PK for the n-th test day
MH Adjusted span reading at 20% of URL on the n-th test day
MSD Span drift at 20* of URL
n Subscript indicating the test day number
P Analyzer reading for precision test
P^ The 4,-th analyzer reading for precision test
Pao Precision at 202 of URL
Peo Precision at 80% of URL
R Analyzer reading of pollutant alone for IE test
R! Analyzer reading with interferent added for IE test
ri The JL-tii DM reading for noise test
S Standard deviation of noise readings
S0 Noise value (S) measured at 0 concentration
Seo Noise value (S) measured at 80% of URL
S,, Average of P7...Pi2 for the n-th test day
S;[ Adjusted span reading at 80% of URL on the n-th test day
URL Upper range limit
USD Span drift at 80% of URL
Z Average of L-, and L«
Zn Average of L-j and L2 on the n-th test day
Z;£ Adjusted zero reading on the n-th test day
ZD Zero drift
12ZD 12-hour zero drift
24ZD 24-hour zero drift
40
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-650/4-74-018
2.
3. RECIPIENT'S ACCESSION-NO.
'
ui Defines tar Determining Performance Characteristics
of Automated Methods for Measuring Nitrogen Dioxide and
Hydrocarbons Corrected for Methane in Ambient Air
5. REPORT DATE
November 1974
6. PERFORMING ORGANIZATION CODE
7 AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Quality Assurance and Environmental Monitoring Lab.
National Environmental Research Center
Research Triangle Park, North Carolina 27711
10. PROGRAM ELEMENT NO.
1HA327
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
Recommended performance specification and test procedures are given for range, noise,
lower detectable limit, interference equivalent, zero drift, span drift, lag time,
rise time, fall time, and precision for automated methods for measuring nitrogen
dioxide and hydrocarbons corrected for methane.
These specifications and test procedures are intended for use as guidelines to assist
instrument manufacturers and instrument users to determine performance characteristics
for continuous air monitoring analyzers.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b IDENTIFIERS/OPEN ENDED TERMS
c. COS AT I Field/Group
Performance specification
Nitrogen dioxide
Hydrocarbons
Air monitoring analyzers
18 DISTRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
46
20 SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
41
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