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(continued)

5.3.1 Single Sampler Precision.

5.3.1.1 At low concentrations, agreement between the measurements of collocated samplers, expressed as percent differences, may be relatively poor. For this reason, collocated measurement pairs are selected for use in the precision calculations only when both measurements are above the following limits:

(a) TSP: 20 µg/m3.

(b) SO2: 45 µg/m3.

(c) NO2: 30 µg/m3.

(d) Pb: 0.15 µg/m3.

(e) PM10: 20 µg/m3.

5.3.1.2 For each selected measurement pair, the percent difference (di) is calculated, using equation 10, as follows:

Equation 10
where:

Yi is the pollutant concentration measurement obtained from the duplicate sampler; and

Xi is the concentration measurement obtained from the primary sampler designated for reporting air quality for the site.

(a) For each site, the quarterly average percent difference (dj) is calculated from equation 2 and the standard deviation (Sj) is calculated from equation 3, where n= the number of selected measurement pairs at the site.

5.3.2 Precision for Reporting Organization.

5.3.2.1 For each pollutant, the average percentage difference (D) and the pooled standard deviation (Sa) are calculated, using equations 4 and 5, or using equations 4a and 5a if different numbers of paired measurements are obtained at the collocated sites. For these calculations, the k of equations 4, 4a, 5 and 5a is the number of collocated sites.

5.3.2.2 The 95 Percent Probability Limits for the integrated precision for a reporting organization are calculated using equations 11 and 12, as follows:

Equation 11 Equation 12
5.4 Accuracy of Manual Methods Excluding PM2.5. Estimates of the accuracy of manual methods are calculated from the results of independent audits as described in section 3.4 of this appendix. At the end of each calendar quarter, an integrated accuracy probability interval is calculated for each manual method network operated by the reporting organization.

5.4.1 Particulate Matter Samplers other than PM2.5 (including reference method Pb samplers).

5.4.1.1 Single Sampler Accuracy. For the flow rate audit described in section 3.4.1 of this appendix, the percentage difference (di) for each audit is calculated using equation 1, where Xi represents the known flow rate and Yi represents the flow rate indicated by the sampler.

5.4.1.2 Accuracy for Reporting Organization. For each type of particulate matter measured (e.g., TSP/Pb), the average (D) of the individual percent differences for all similar particulate matter samplers audited during the calendar quarter is calculated using equation 8. The standard deviation (Sa) of the percentage differences for all of the similar particulate matter samplers audited during the calendar quarter is calculated using equation 9. The 95 Percent Probability Limits for the integrated accuracy for the reporting organization are calculated using equations 6 and 7. For reporting organizations having four or fewer particulate matter samplers of one type, only one audit is required each quarter, and the audit results of two consecutive quarters are required to calculate an average and a standard deviation. In that case, probability limits shall be reported semi-annually rather than quarterly.

5.4.2 Analytical Methods for SO2, NO2, and Pb.

5.4.2.1 Single Analysis-Day Accuracy. For each of the audits of the analytical methods for SO2, NO2, and Pb described in sections 3.4.2, 3.4.3, and 3.4.4 of this appendix, the percentage difference (dj) at each concentration level is calculated using equation 1, where Xj represents the known value of the audit sample and Yj represents the value of SO2, NO2, or Pb indicated by the analytical method.

5.4.2.2 Accuracy for Reporting Organization. For each analytical method, the average (D) of the individual percent differences at each concentration level for all audits during the calendar quarter is calculated using equation 8. The standard deviation (Sa) of the percentage differences at each concentration level for all audits during the calendar quarter is calculated using equation 9. The 95 Percent Probability Limits for the accuracy for the reporting organization are calculated using equations 6 and 7.

5.5 Precision, Accuracy and Bias for Automated and Manual PM2.5 Methods.

(a) Reporting organizations are required to report the data that will allow assessments of the following individual quality control checks and audits:

(1) Flow rate audit.

(2) Collocated samplers, where the duplicate sampler is not an FRM device.

(3) Collocated samplers, where the duplicate sampler is an FRM device.

(4) FRM audits.

(b) EPA uses the reported results to derive precision, accuracy and bias estimates according to the following procedures.

5.5.1 Flow Rate Audits. The reporting organization shall report both the audit standard flow rate and the flow rate indicated by the sampling instrument. These results are used by EPA to calculate flow rate accuracy and bias estimates.

5.5.1.1 Accuracy of a Single Sampler - Single Check (Quarterly) Basis (di). The percentage difference (di) for a single flow rate audit di is calculated using equation 13, where Xi represents the audit standard flow rate (known) and Yi represents the indicated flow rate, as follows:

Equation 13
5.5.1.2 Bias of a Single Sampler - Annual Basis (Dj). For an individual particulate sampler j, the average (Dj) of the individual percentage differences (di) during the calendar year is calculated using equation 14, where nj is the number of individual percentage differences produced for sampler j during the calendar year, as follows:

Equation 14
5.5.1.3 Bias for Each EPA Federal Reference and Equivalent Method Designation Employed by Each Reporting Organization - Quarterly Basis (Dk,q). For method designation k used by the reporting organization, quarter q's single sampler percentage differences (di) are averaged using equation 16, where nk,q is the number of individual percentage differences produced for method designation k in quarter q, as follows:

Equation 15
5.5.1.4 Bias for Each Reporting Organization - Quarterly Basis (Dq). For each reporting organization, quarter q's single sampler percentage differences (di) are averaged using equation 16, to produce a single average for each reporting organization, where nq is the total number of single sampler percentage differences for all federal reference or equivalent methods of samplers in quarter q, as follows:

Equation 16
5.5.1.5 Bias for Each EPA Federal Reference and Equivalent Method Designation Employed by Each Reporting Organization - Annual Basis (Dk). For method designation k used by the reporting organization, the annual average percentage difference, Dk, is derived using equation 17, where Dk,q is the average reported for method designation k during the qth quarter, and nk,q is the number of the method designation k's monitors that were deployed during the qth quarter, as follows:

Equation 17
5.5.1.6 Bias for Each Reporting Organization - Annual Basis (D). For each reporting organization, the annual average percentage difference, D, is derived using equation 18, where Dq is the average reported for the reporting organization during the qth quarter, and nq is the total number monitors that were deployed during the qth quarter. A single annual average is produced for each reporting organization. Equation 18 follows:

Equation 18
5.5.2 Collocated Samplers, Where the Duplicate Sampler is not an FRM Device. (a) At low concentrations, agreement between the measurements of collocated samplers may be relatively poor. For this reason, collocated measurement pairs are selected for use in the precision calculations only when both measurements are above the following limits:

PM2.5 : 6 µg/m3

(b) Collocated sampler results are used to assess measurement system precision. A collocated sampler pair consists of a primary sampler (used for routine monitoring) and a duplicate sampler (used as a quality control check). Quarterly precision estimates are calculated by EPA for each pair of collocated samplers and for each method designation employed by each reporting organization. Annual precision estimates are calculated by EPA for each primary sampler, for each EPA Federal reference method and equivalent method designation employed by each reporting organization, and nationally for each EPA Federal reference method and equivalent method designation.

5.5.2.1 Percent Difference for a Single Check (di). The percentage difference, di, for each check is calculated by EPA using equation 19, where Xi represents the concentration produced from the primary sampler and Yi represents concentration reported for the duplicate sampler, as follows:

Equation 19
5.5.2.2 Coefficient of Variation (CV) for a Single Check (CVi). The coefficient of variation, CVi, for each check is calculated by EPA by dividing the absolute value of the percentage difference, di, by the square root of two as shown in equation 20, as follows:

Equation 20
5.5.2.3 Precision of a Single Sampler - Quarterly Basis (CVj,q).

(a) For particulate sampler j, the individual coefficients of variation (CVj,q) during the quarter are pooled using equation 21, where nj,q is the number of pairs of measurements from collocated samplers during the quarter, as follows:

Equation 21
(b) The 90 percent confidence limits for the single sampler's CV are calculated by EPA using equations 22 and 23, where X2 0.05,df and X2 0.95,df are the 0.05 and 0.95 quantiles of the chi-square (X2) distribution with nj,q degrees of freedom, as follows:

Equation 22 Equation 23
5.5.2.4 Precision of a Single Sampler - Annual Basis. For particulate sampler j, the individual coefficients of variation, CVi, produced during the calendar year are pooled using equation 21, where nj is the number of checks made during the calendar year. The 90 percent confidence limits for the single sampler's CV are calculated by EPA using equations 22 and 23, where X2 0.05,df and X2 0.95,df are the 0.05 and 0.95 quantiles of the chi-square (X2) distribution with nj degrees of freedom.

5.5.2.5 Precision for Each EPA Federal Reference Method and Equivalent Method Designation Employed by Each Reporting Organization - Quarterly Basis (CVk,q).

(a) For each method designation k used by the reporting organization, the quarter's single sampler coefficients of variation, CVj,qs, obtained from equation 21, are pooled using equation 24, where nk,q is the number of collocated primary monitors for the designated method (but not collocated with FRM samplers) and nj,q is the number of degrees of freedom associated with CVj,q, as follows:

Equation 24
(b) The number of method CVs produced for a reporting organization will equal the number of different method designations having more than one primary monitor employed by the organization during the quarter. (When exactly one monitor of a specified designation is used by a reporting organization, it will be collocated with an FRM sampler.)

5.5.2.6 Precision for Each Method Designation Employed by Each Reporting Organization - Annual Basis (CVk). For each method designation k used by the reporting organization, the quarterly estimated coefficients of variation, CVk,q, are pooled using equation 25, where nk,q is the number of collocated primary monitors for the designated method during the qth quarter and also the number of degrees of freedom associated with the quarter's precision estimate for the method designation, CVk,q, as follows:

Equation 25
5.5.3 Collocated Samplers, Where the Duplicate Sampler is an FRM Device. At low concentrations, agreement between the measurements of collocated samplers may be relatively poor. For this reason, collocated measurement pairs are selected for use in the precision calculations only when both measurements are above the following limits: PM2.5: 6 µg/m3. These duplicate sampler results are used to assess measurement system bias. Quarterly bias estimates are calculated by EPA for each primary sampler and for each method designation employed by each reporting organization. Annual precision estimates are calculated by EPA for each primary monitor, for each method designation employed by each reporting organization, and nationally for each method designation.

5.5.3.1 Accuracy for a Single Check (d'i). The percentage difference, d'i, for each check is calculated by EPA using equation 26, where Xi represents the concentration produced from the FRM sampler taken as the true value and Yi represents concentration reported for the primary sampler, as follows:

Equation 26
5.5.3.2 Bias of a Single Sampler - Quarterly Basis (D'j,q).

(a) For particulate sampler j, the average of the individual percentage differences during the quarter q is calculated by EPA using equation 27, where nj,q is the number of checks made for sampler j during the calendar quarter, as follows:

Equation 27
(b) The standard error, s'j,q, of sampler j's percentage differences for quarter q is calculated using equation 28, as follows:

Equation 28
(c) The 95 Percent Confidence Limits for the single sampler's bias are calculated using equations 29 and 30 where t0.975,df is the 0.975 quantile of Student's t distribution with df = nj,q-1 degrees of freedom, as follows:

Equation 29 Equation 30
5.5.3.3 Bias of a Single Sampler - Annual Basis (D'j).

(a) For particulate sampler j, the mean bias for the year is derived from the quarterly bias estimates, D'j,q, using equation 31, where the variables are as defined for equations 27 and 28, as follows:

Equation 31
(b) The standard error of the above estimate, sej' is calculated using equation 32, as follows:

Equation 32
(c) The 95 Percent Confidence Limits for the single sampler's bias are calculated using equations 33 and 34, where t0.975,df is the 0.975 quantile of Student's t distribution with df = (nj,1 + nj,2 + nj,3 + nj,4-4) degrees of freedom, as follows:

Equation 33 Equation 34
5.5.3.4 Bias for a Single Reporting Organization (D') - Annual Basis. The reporting organizations mean bias is calculated using equation 35, where variables are as defined in equations 31 and 32, as follows:

Equation 35
5.5.4 FRM Audits. FRM Audits are performed once per quarter for selected samplers. The reporting organization reports concentration data from the primary sampler. Calculations for FRM Audits are similar to those for collocated samplers having FRM samplers as duplicates. The calculations differ because only one check is performed per quarter.

5.5.4.1 Accuracy for a Single Sampler, Quarterly Basis (di). The percentage difference, di, for each check is calculated using equation 26, where Xi represents the concentration produced from the FRM sampler and Yi represents the concentration reported for the primary sampler. For quarter q, the bias estimate for sampler j is denoted Dj,q.

5.5.4.2 Bias of a Single Sampler - Annual Basis (D'j). For particulate sampler j, the mean bias for the year is derived from the quarterly bias estimates, Dj,q, using equation 31, where nj,q equals 1 because one FRM audit is performed per quarter.

5.5.4.3. Bias for a Single Reporting Organization - Annual Basis (D'). The reporting organizations mean bias is calculated using equation 35, where variables are as defined in equations 31 and 32.

References in Appendix A of Part 58

(1) Rhodes, R.C. Guideline on the Meaning and Use of Precision and Accuracy Data Required by 40 CFR part 58, Appendices A and B. EPA-600/4-83/023. U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, June, 1983.

(2) American National Standard—Specifications and Guidelines for Quality Systems for Environmental Data Collection and Environmental Technology Programs. ANSI/ASQC E4-1994. January 1995. Available from American Society for Quality Control, 611 East Wisconsin Avenue, Milwaukee, WI 53202.

(3) EPA Requirements for Quality Management Plans. EPA QA/R-2. August 1994. Available from U.S. Environmental Protection Agency, ORD Publications Office, Center for Environmental Research Information (CERI), 26 W. Martin Luther King Drive, Cincinnati, OH 45268.

(4) EPA Requirements for Quality Assurance Project Plans for Environmental Data Operations. EPA QA/R-5. August 1994. Available from U.S. Environmental Protection Agency, ORD Publications Office, Center for Environmental Research Information (CERI), 26 W. Martin Luther King Drive, Cincinnati, OH 45268.

(5) Guidance for the Data Quality Objectives Process. EPA QA/G-4. September 1994. Available from U.S. Environmental Protection Agency, ORD Publications Office, Center for Environmental Research Information (CERI), 26 W. Martin Luther King Drive, Cincinnati, OH 45268.

(6) Quality Assurance Handbook for Air Pollution Measurement Systems, Volume 1—A Field Guide to Environmental Quality Assurance. EPA-600/R-94/038a. April 1994. Available from U.S. Environmental Protection Agency, ORD Publications Office, Center for Environmental Research Information (CERI), 26 W. Martin Luther King Drive, Cincinnati, OH 45268.

(7) Quality Assurance Handbook for Air Pollution Measurement Systems, Volume II—Ambient Air Specific Methods EPA-600/R-94/038b. Available from U.S. Environmental Protection Agency, ORD Publications Office, Center for Environmental Research Information (CERI), 26 W. Martin Luther King Drive, Cincinnati, OH 45268.

(7a) Copies of section 2.12 of the Quality Assurance Handbook for Air Pollution Measurement Systems, are available from Department E (MD-77B), U.S. EPA, Research Triangle Park, NC 27711.

(8) List of Designated Reference and Equivalent Methods. Available from U.S. Environmental Protection Agency, National Exposure Research Laboratory, Quality Assurance Branch, MD-77B, Research Triangle Park, NC 27711.

(9) Technical Assistance Document for Sampling and Analysis of Ozone Precursors. Atmospheric Research and Exposure Assessment Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711. EPA 600/8-91-215. October 1991.

(10) EPA Traceability Protocol for Assay and Certification of Gaseous Calibration Standards. EPA-600/R-93/224. September 1993. Available from U.S. Environmental Protection Agency, ORD Publications Office, Center for Environmental Research Information (CERI), 26 W. Martin Luther King Drive, Cincinnati, OH 45268.

(11) Paur, R.J. and F.F. McElroy. Technical Assistance Document for the Calibration of Ambient Ozone Monitors. EPA-600/4-79-057. U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, September, 1979.

(12) McElroy, F.F. Transfer Standards for the Calibration of Ambient Air Monitoring Analyzers for Ozone. EPA-600/4-79-056. U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, September, 1979.

(13) Musick, D.R. The Ambient Air Precision and Accuracy Program: 1995 Annual Report. EPA-454/R97001. U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, February 1997.

(14) Papp, M.L., J,B., Elkins, D.R., Musick and M.J., Messner, Data Quality Objectives for the PM2.5. Monitoring Data, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711. In preparation.

(15) Photochemical Assessment Monitoring Stations Implementation Manual. EPA-454/B-93-051, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, March 1994.


Table A-1 to Appendix A_Minimum Data Assessment Requirements
----------------------------------------------------------------------------------------------------------------
Method Assessment Method Coverage Minimum Frequency Parameters Reported
----------------------------------------------------------------------------------------------------------------
Precision:
Automated Methods Response check at Each analyzer Once per 2 weeks Actual concentration
for SO2, NO2, concentration \2\ and measured
O3, and CO between .08 and .10 concentration \3\
ppm (8 & 10 ppm
for CO) \2\
Manual Methods: Collocated samplers 1 site for 1-5 sites Once every six days Particle mass
All methods 2 sites for 6-20 concentration
except PM2.5 sites indicated by
3 sites >20 sites sampler and by
(sites with highest collocated sampler
conc.)
Accuracy:
Automated Methods Response check at 1. Each analyzer 1. Once per year Actual concentration
for SO2, NO2, .03-.08 ppm1,2 2. 25% of analyzers 2. Each calendar \2\ and measured
O3, and CO .15-.20 ppm1,2 (at least 1) quarter (indicated)
.35-.45 ppm1,2 concentration \3\
80-.90 ppm1,2 (if for each level
applicable)
Manual Methods Check of analytical Analytical system Each day samples are Actual concentration
for SO2, and NO2 procedure with audit analyzed, at least and measured
standard solutions twice per quarter (indicated)
concentration for
each audit solution
TSP, PM10 Check of sampler flow 1. Each sampler 1. Once per year Actual flow rate and
rate 2. 25% of samplers 2. Each calendar flow rate indicated
(at least 1) quarter by the sampler
Lead 1. Check of sample 1. Each sampler 1. Include with TSP 1. Same as for TSP
flow rate as for TSP
2. Check of 2. Analytical system 2. Each quarter 2. Actual
analytical system concentration and
with Pb audit strips measured
(indicated)
concentration of
audit samples
(µg Pb/strip)
PM2.5
Manual and Collocated samplers 25% of SLAMS Once every six days 1. Particle mass
Automated (monitors with Conc concentration
Methods- affecting NAAQS indicated by
Precision violation status) sampler and by
collocated sampler
2. 24-hour value for
automated methods
Manual and 1. Check of sampler Every SLAMS monitor 1. Automated_once 1. Actual flow rate
Automated flow rate every 2 weeks; and flow rate
Methods-Accuracy Manual_each calendar indicated by
and Bias quarter (4/year) sampler
2. Audit with ..................... 2. Minimum 4 2. Particle mass
reference method measurements per concentration
year indicated by
sampler and by
audit reference
sampler
----------------------------------------------------------------------------------------------------------------
\1\ Concentration times 100 for CO.
\2\ Effective concentration for open path analyzers.
\3\ Corrected concentration, if applicable, for open path analyzers.




Table A-2 to Appendix A_Summary of PM2.5 Collocation and Audits Procedures As an Example of a Typical Reporting
Organization Needing 43 Monitors, Having Procured FRMs and Three Other Equivalent Method Types
----------------------------------------------------------------------------------------------------------------
# of Collocated
Method Designation Total # of Total # # of Collocated Monitors of Same # of Independent
Monitors Collocated FRMs Type FRM Audits
----------------------------------------------------------------------------------------------------------------
FRM 25 6 6 n/a 6
Type A 10 3 2 1 3
Type C 2 1 1 0 1
Type D 6 2 1 1 2
----------------------------------------------------------------------------------------------------------------


[62 FR 38833, July 18, 1997; 63 FR 7714, 7715, Feb. 17, 1998; 68 FR 80328, Dec. 31, 2002]

Appendix B to Part 58—Quality Assurance Requirements for Prevention of Significant Deterioration (PSD) Air Monitoring
top
1. General Information

This appendix specifies the minimum quality assurance requirements for the control and assessment of the quality of the PSD ambient air monitoring data submitted to EPA by an organization operating a network of PSD stations. Such organizations are encouraged to develop and maintain quality assurance programs more extensive than the required minimum.

Quality assurance of air monitoring systems includes two distinct and important interrelated functions. One function is the control of the measurement process through the implementation of policies, procedures, and corrective actions. The other function is the assessment of the quality of the monitoring data (the product of the measurement process). In general, the greater the effort and effectiveness of the control of a given monitoring system, the better will be the resulting quality of the monitoring data. The results of data quality assessments indicate whether the control efforts need to be increased.

Documentation of the quality assessments of the monitoring data is important to data users, who can then consider the impact of the data quality in specific applications (see Reference 1). Accordingly, assessments of PSD monitoring data quality are required to be made and reported periodically by the monitoring organization.

To provide national uniformity in the assessment and reporting of data quality among all PSD networks, specific assessment and reporting procedures are prescribed in detail in sections 3, 4, 5, and 6 of this appendix.

In contrast, the control function encompasses a variety of policies, procedures, specifications, standards, and corrective measures which affect the quality of the resulting data. The selection and extent of the quality control activities—as well as additional quality assessment activities—used by a monitoring organization depend on a number of local factors such as the field and laboratory conditions, the objectives of the monitoring, the level of the data quality needed, the expertise of assigned personnel, the cost of control procedures, pollutant concentration levels, etc. Therefore, the quality assurance requirements, in section 2 of this appendix, are specified in general terms to allow each organization to develop a quality control system that is most efficient and effective for its own circumstances.

For purposes of this appendix, “organization” is defined as a source owner/operator, a government agency, or their contractor that operates an ambient air pollution monitoring network for PSD purposes.

2. Quality Assurance Requirements

2.1 Each organization must develop and implement a quality assurance program consisting of policies, procedures, specifications, standards and documentation necessary to:

(1) Provide data of adequate quality to meet monitoring objectives and quality assurance requirements of the permit-granting authority, and

(2) Minimize loss of air quality data due to malfunctions or out-of-control conditions.

This quality assurance program must be described in detail, suitably documented, and approved by the permit-granting authority. The Quality Assurance Program will be reviewed during the system audits described in section 2.4.

2.2 Primary guidance for developing the Quality Assurance Program is contained in References 2 and 3, which also contain many suggested procedures, checks, and control specifications. Section 2.0.9 of Reference 3 describes specific guidance for the development of a Quality Assurance Program for automated analyzers. Many specific quality control checks and specifications for manual methods are included in the respective reference methods described in part 50 of this chapter or in the respective equivalent method descriptions available from EPA (see Reference 4). Similarly, quality control procedures related to specifically designated reference and equivalent analyzers are contained in their respective operation and instruction manuals. This guidance, and any other pertinent information from appropriate sources, should be used by the organization in developing its quality assurance program.

As a minimum, each quality assurance program must include operational procedures for each of the following activities:

(1) Selection of methods, analyzers, or samplers;

(2) Training;

(3) Installation of equipment;

(4) Selection and control of calibration standards;

(5) Calibration;

(6) Zero/span checks and adjustments of automated analyzers;

(7) Control checks and their frequency;

(8) Control limits for zero, span and other control checks, and respective corrective actions when such limits are surpassed;

(9) Calibration and zero/span checks for multiple range analyzers (see section 2.6 of appendix C of this part);

(10) Preventive and remedial maintenance;

(11) Recording and validating data;

(12) Date quality assessment (precision and accuracy);

(13) Documentation of quality control information.

2.3 Pollutant Standards.

2.3.1 Gaseous standards (permeation tubes, permeation devices or cylinders of compressed gas) used to obtain test concentrations for CO, SO2, and NO2 must be traceable to either a National Institute of Standards and Technology (NIST) gaseous Standard Reference Material (SRM) or an NIST/EPA-approved commercially available Certified Reference Material (CRM). CRM's are described in Reference 5, and a list of CRM sources is available from Quality Assurance Division (MD–77), Atmospheric Research and Exposure Assessment Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711. A recommended protocol for certifying gaseous standards against an SRM or CRM is given in section 2.0.7 of Reference 3. Direct use of a CRM as a working standard is acceptable, but direct use of an NIST SRM as a working standard is discouraged because of the limited supply and expense of SRM's.

2.3.2 Test concentrations for ozone must be obtained in accordance with the UV photometric calibration procedure specified in appendix D of part 50 of this chapter, or by means of a certified ozone transfer standard. Consult References 6 and 7 for guidance on primary and transfer standards for ozone.

2.3.3. Flow measurement must be made by a flow measuring instrument that is traceable to an authoritative volume or other standard. Guidance for certifying various types of flowmeters is provided in Reference 3.

2.4 Performance and System Audit Programs. The organization operating a PSD monitoring network must participate in EPA's national performance audit program. The permit granting authority, or EPA, may conduct system audits of the ambient air monitoring programs of organizations operating PSD networks. See section 1.4.16 of reference 2 and section 2.0.11 of reference 3 for additional information about these programs. Organizations should contact either the appropriate EPA Regional Quality Control Coordinator or the Quality Assurance Branch, AREAL/RTP, at the address given in reference 3 for instructions for participation.

3. Data Quality Assessment Requirements

All ambient monitoring methods or analyzers used in PSD monitoring shall be tested periodically, as described in this section 3, to quantitatively assess the quality of the data being routinely collected. The results of these tests shall be reported as specified in section 6. Concentration standards used for the tests must be as specified in section 2.3. Additional information and guidance in the technical aspects of conducting these tests may be found in Reference 3 or in the operation or instruction manual associated with the analyzer or sampler. Concentration measurements reported from analyzers or analytical systems must be derived by means of the same calibration curve and data processing system used to obtain the routine air monitoring data. Table B–1 provides a summary of the minimum data quality assessment requirements, which are described in more detail in the following sections.

3.1 Precision of Automated Methods. A one-point precision check must be carried out at least once every two weeks on each automated analyzer used to measure SO2, NO2, O2, and CO. The precision check is made by challenging the analyzer with a precision check gas of known concentration (effective concentration for open path analyzers) between 0.08 and 0.10 ppm for SO2, NO2, and O3 analyzers, and between 8 and 10 ppm for CO analyzers. The standards from which precision check test concentrations are obtained must meet the specifications of section 2.3. Except for certain CO analyzers described below, point analyzers must operate in their normal sampling mode during the precision check, and the test atmosphere must pass through all filters, scrubbers, conditioners and other components used during normal ambient sampling and as much of the ambient air inlet system as is practicable. If permitted by the associated operation or instruction manual, a CO point analyzer may be temporarily modified during the precision check to reduce vent or purge flows, or the test atmosphere may enter the analyzer at a point other than the normal sample inlet, provided that the analyzer's response is not likely to be altered by these deviations from the normal operational mode.

Open path analyzers are tested by inserting a test cell containing a precision check gas concentration into the optical measurement beam of the instrument. If possible, the normally used transmitter, receiver, and, as appropriate, reflecting devices should be used during the test, and the normal monitoring configuration of the instrument should be altered as little as possible to accommodate the test cell for the test. However, if permitted by the associated operation or instruction manual, an alternate local light source or an alternate optical path that does not include the normal atmospheric monitoring path may be used. The actual concentration of the precision check gas in the test cell must be selected to produce an “effective concentration” in the range specified above. Generally, the precision test concentration measurement will be the sum of the atmospheric pollutant concentration and the precision test concentration. If so, the result must be corrected to remove the atmospheric concentration contribution. The “corrected concentration” is obtained by subtracting the average of the atmospheric concentrations measured by the open path instrument under test immediately before and immediately after the precision check test from the precision test concentration measurement. If the difference between these before and after measurements is greater than 20 percent of the effective concentration of the test gas, discard the test result and repeat the test. If possible, open path analyzers should be tested during periods when the atmospheric pollutant concentrations are relatively low and steady.

If a precision check is made in conjunction with a zero or span adjustment, it must be made prior to such zero or span adjustment. The difference between the actual concentration (effective concentration for open path analyzers) of the precision check gas and the corresponding concentration measurement (corrected concentration, if applicable, for open path analyzers) indicated by the analyzer is used to assess the precision of the monitoring data as described in section 4.1. Report data only from automated analyzers that are approved for use in the PSD network.

3.2 Accuracy of Automated Methods. Each sampling quarter, audit each analyzer that monitors for SO2, NO2, O3, or CO at least once. The audit is made by challenging the analyzer with at least one audit gas of known concentration (effective concentration for open path analyzers) from each of the following ranges that fall within the measurement range of the analyzer being audited:



------------------------------------------------------------------------
Concentration range, ppm
Audit level -------------------------- CO
SO2, O3, NO2,
------------------------------------------------------------------------
1.................................. 0.03-0.08 0.03-0.08 3-8
2.................................. 0.15-0.20 0.15-0.20 15-20
3.................................. 0.36-0.45 0.35-0.45 35-45
4.................................. 0.80-0.90 ........... 80-90
------------------------------------------------------------------------


NO2 audit gas for chemiluminescence-type NO2 analyzers must also contain at least 0.08 ppm NO.

Note: NO concentrations substantially higher than 0.08 ppm, as may occur when using some gas phase titration (GPT) techniques, may lead to audit errors in chemiluminescence analyzers due to inevitable minor NO-NOX channel imbalance. Such errors may be atypical of routine monitoring errors to the extent that such NO concentrations exceed typical ambient NO concentrations. These errors may be minimized by modifying the GPT technique to lower the NO concentrations remaining in the NO2 audit gas to levels closer to typical ambient NO concentrations at the site.

The standards from which audit gas test concentrations are obtained must meet the specifications of section 2.3. Working and transfer standards and equipment used for auditing must be different from the standards and equipment used for calibration and spanning. The auditing standards and calibration standards may be referenced to the same NIST, SRM, CRM, or primary UV photometer. The auditor must not be the operator/analyst who conducts the routine monitoring, calibration and analysis.

For point analyzers, the audit shall be carried out by allowing the analyzer to analyze the audit test atmosphere in the same manner as described for precision checks in section 3.1. The exception given in section 3.1 for certain CO analyzers does not apply for audits.

Open path analyzers are audited by inserting a test cell containing an audit gas concentration into the optical measurement beam of the instrument. If possible, the normally used transmitter, receiver, and, as appropriate, reflecting devices should be used during the audit, and the normal monitoring configuration of the instrument should be modified as little as possible to accommodate the test cell for the audit. However, if permitted by the associated operation or instruction manual, an alternate local light source or an alternate optical path that does not include the normal atmospheric monitoring path may be used. The actual concentrations of the audit gas in the test cell must be selected to produce “effective concentrations” in the range specified in this section 3.2. Generally, each audit concentration measurement result will be the sum of the atmospheric pollutant concentration and the audit test concentration. If so, the result must be corrected to remove the atmospheric concentration contribution. The “corrected concentration” is obtained by subtracting the average of the atmospheric concentrations measured by the open path instrument under test immediately before and immediately after the audit test (or preferably before and after each audit concentration level) from the audit concentration measurement. If the difference between these before and after measurements is greater than 20 percent of the effective concentration of the test gas standards, discard the test result for that concentration level and repeat the test for that level. If possible, open path analyzers should be audited during periods when the atmospheric pollutant concentrations are relatively low and steady. Also, the monitoring path length must be reverified to within ±3 percent to validate the audit, since the monitoring path length is critical to the determination of the effective concentration.

The differences between the actual concentrations (effective concentrations for open path analyzers) of the audit test gas and the corresponding concentration measurements (corrected concentrations, if applicable, for open path analyzers) indicated by the analyzer are used to assess the accuracy of the monitoring data as described in section 4.2. Report data only from automated analyzers that are approved for use in the PSD network.

3.3 Precision of Manual Methods.

3.3.1 TSP and PM10 Methods. For a given organization's monitoring network, one sampling site must have collocated samplers. A site with the highest expected 24-hour pollutant concentration must be selected. The two samplers must be within 4 meters of each other but at least 2 meters apart to preclude airflow interference. Calibration, sampling and analysis must be the same for both collocated samplers as well as for all other samplers in the network. The collocated samplers must be operated as a minimum every third day when continuous sampling is used. When a less frequent sample schedule is used, the collocated samplers must be operated at least once each week. For each pair of collocated samplers, designate one sampler as the sampler which will be used to report air quality for the site and designate the other as the duplicate sampler. The differences in measured concentration (µg/m 3 ) between the two collocated samplers are used to calculate precision as described in section 5.1.

3.3.2 Pb Method. The operation of collocated samplers at one sampling site must be used to assess the precision of the reference or an equivalent Pb method. The procedure to be followed for Pb methods is the same as described in 3.3.1 for the TSP method. If approved by the permit granting authority, the collocated TSP samplers may serve as the collocated lead samplers.

3.4 Accuracy of Manual Methods.

3.4.1 TSP and PM10 Methods. Each sampling quarter, audit the flow rate of each sampler at least once. Audit the flow at the normal flow rate, using a certified flow transfer standard (see reference 2). The flow transfer standard used for the audit must not be the same one used to calibrate the flow of the sampler being audited, although both transfer standards may be referenced to the same primary flow or volume standard. The difference between the audit flow measurement and the flow indicated by the sampler's flow indicator is used to calculate accuracy, as described in paragraph 5.2.

Great care must be used in auditing high-volume samplers having flow regulators because the introduction of resistance plates in the audit device can cause abnormal flow patterns at the point of flow sensing. For this reason, the orifice of the flow audit device should be used with a normal glass fiber filter in place and without resistance plates in auditing flow regulated high-volume samplers, or other steps should be taken to assure that flow patterns are not perturbed at the point of flow sensing.

3.4.2 Pb Method. For the reference method (appendix G of part 50 of this chapter) during each sampling quarter audit the flow rate of each high-volume Pb sampler at least once. The procedure to be followed for lead methods is the same as described in section 3.4.1 for the TSP method.

For each sampling quarter, audit the Pb analysis using glass fiber filter strips containing a known quantity of lead. Audit samples are prepared by depositing a Pb solution on 1.9 cm by 20.3 cm ( 3/4 inch by 8 inch) unexposed glass fiber filter strips and allowing to dry thoroughly. The audit samples must be prepared using reagents different from those used to calibrate the Pb analytical equipment being audited. Prepare audit samples in the following concentration ranges:



------------------------------------------------------------------------
Equivalent ambient
Ranges Pb concentration Pb concentration
µg/strip \1\ µg/m \3\
------------------------------------------------------------------------
1............................... 100 to 300........ 0.5 to 1.5.
2............................... 600 to 1,000...... 3.0 to 5.0.
------------------------------------------------------------------------
\1\ Equivalent ambient Pb concentration in µg/m\3\ is based on
sampling at 1.7 m\3\/min for 24 hours on 20.3 cm x 25.4 cm (8 inch x
10 inch) glass fiber filter.


Audit samples must be extracted using the same extraction procedure used for exposed filters.

Analyze at least one audit sample in each of the two ranges each day that samples are anlayzed. The difference between the audit concentration (in mu;g Pb/strip) and the analyst's measured concentration (in mu;g Pb/strip is used to calculate accuracy as described in section 5.4.

The accuracy of an equivalent method is assessed in the same manner as the reference method. The flow auditing device and Pb analysis audit samples must be compatible with the specific requirements of the equivalent method.

4. Calculations for Automated Methods

4.1 Single Analyzer Precision. Each organization, at the end of each sampling quarter, shall calculate and report a precision probability interval for each analyzer. Directions for calculations are given below and directions for reporting are given in section 6. If monitoring data are invalidated during the period represented by a given precision check, the results of that precision check shall be excluded from the calculations. Calculate the percentage difference (di) for each precision check using equation 1.


where:

Yi = analyzer's indicated concentration from the i-th precision check

Xi = known concentration of the test gas used for the i-th precision check.

For each instrument, calculate the quarterly average (dj), equation 2, and the standard deviation (Sj), equation 3.


where n is the number of precision checks on the instrument made during ther sampling quarter. For example, n should be 6 or 7 if span checks are made biweekly during a quarter.

Calculate the 95 percent probability limits for precision using equation 4 and 5.

Upper 95 Percent Probability

Limit = dj+1.96 Sj

(4)
Lower 95 Percent Probability

Limit = dj-1.96 Sj

(5)
4.2 Single Analyzer Accuracy. Each organization, at the end of each sampling quarter, shall calculate and report the percentage difference for each audit concentration for each analyzer audited during the quarter. Directions for calculations are given below (directions for reporting are given in section 6).

Calculate and report the percentage difference (di) for each audit concentration using equation 1 where Yi is the analyzer's indicated concentration from the i-th audit check and Xi is the known concentration of the audit gas used for the i-th audit check.

5. Calculations for Manual Methods

5.1 Single Instrument Precision for TSP, Pb and PM10. Estimates of precision for ambient air quality particulate measurements are calculated from results obtained from collocated samplers as described in section3.3. At the end of each sampling quarter, calculate and report a precision probability interval, using weekly result from the collecated samplers. Directions for calculations are given below, and directions for reporting are given in section 6. (continued)