organization depend on a number of local factors such as field and
laboratory conditions, the objectives for monitoring, the level of
data quality needed, the expertise of assigned personnel, the cost
of control procedures, pollutant concentration levels, etc.
Therefore, quality system requirements in section 2 of this appendix
are specified in general terms to allow each monitoring organization
to develop a quality system that is most efficient and effective for
its own circumstances while achieving the data quality objectives
described in this appendix.

2. Quality System Requirements

    A quality system (reference 1 of this appendix) is the means by
which an organization manages the quality of the monitoring
information it produces in a systematic, organized manner. It
provides a framework for planning, implementing, assessing and
reporting work performed by an organization and for carrying out
required quality assurance and quality control activities.
    2.1 Quality Management Plans and Quality Assurance Project
Plans. All PQAOs must develop a quality system that is described and
approved in quality management plans (QMP) and QAPPs to ensure that
the monitoring results:
    (a) Meet a well-defined need, use, or purpose (reference 5 of
this appendix);
    (b) Provide data of adequate quality for the intended monitoring
objectives;
    (c) Satisfy stakeholder expectations;
    (d) Comply with applicable standards specifications;
    (e) Comply with statutory (and other legal) requirements; and
    (f) Reflect consideration of cost and economics.
    2.1.1 The QMP describes the quality system in terms of the
organizational structure, functional responsibilities of management
and staff, lines of authority, and required interfaces for those
planning, implementing, assessing and reporting activities involving
environmental data operations (EDO). The QMP must be suitably
documented in accordance with EPA requirements (reference 2 of this
appendix), and approved by the appropriate Regional Administrator,
or his or her representative. The quality system described in the
QMP will be reviewed during the systems audits described in section
2.5 of this appendix. Organizations that implement long-term
monitoring programs with EPA funds should have a separate QMP
document. Smaller organizations, organizations that do infrequent
work with the EPA or have monitoring programs of limited size or
scope may combine the QMP with the QAPP if approved by, and subject
to any conditions of the EPA. Additional guidance on this process
can be found in reference 10 of this appendix. Approval of the
recipient's QMP by the appropriate Regional Administrator or his or
her representative may allow delegation of authority to the PQAOs
independent quality assurance function to review and approve
environmental data collection activities adequately described and
covered under the scope of the QMP and documented in appropriate
planning documents (QAPP). Where a PQAO or monitoring organization
has been delegated authority to review and approve their QAPP, an
electronic copy must be submitted to the EPA region at the time it
is submitted to the PQAO/monitoring organization's QAPP approving
authority. The QAPP will be reviewed by the EPA during systems
audits or circumstances related to data quality. The QMP submission
and approval dates for PQAOs/monitoring organizations must be
reported to AQS either by the monitoring organization or the EPA
Region.
    2.1.2 The QAPP is a formal document describing, in sufficient
detail, the quality system that must be implemented to ensure that
the results of work performed will satisfy the stated objectives.
PQAOs must develop QAPPs that describe how the organization intends
to control measurement uncertainty to an appropriate level in order
to achieve the data quality objectives for the EDO. The quality
assurance policy of the EPA requires every EDO to have a written and
approved QAPP prior to the start of the EDO. It is the
responsibility of the PQAO/monitoring organization to adhere to this
policy. The QAPP must be suitably documented in accordance with EPA
requirements (reference 3 of this appendix) and include standard
operating procedures for all EDOs either within the document or by
appropriate reference. The QAPP must identify each PQAO operating
monitors under the QAPP as well as generally identify the sites and
monitors to which it is applicable either within the document or by
appropriate reference. The QAPP submission and approval dates must
be reported to AQS either by the monitoring organization or the EPA
Region.
    2.1.3 The PQAO/monitoring organization's quality system must
have adequate resources both in personnel and funding to plan,
implement, assess and report on the achievement of the requirements
of this appendix and it's approved QAPP.
    2.2 Independence of Quality Assurance. The PQAO must provide for
a quality assurance management function, that aspect of the overall
management system of the organization that determines and implements
the quality policy defined in a PQAO's QMP. Quality management
includes strategic planning, allocation of resources and other
systematic planning activities (e.g., planning, implementation,
assessing and reporting) pertaining to the quality system. The
quality assurance management function must have sufficient technical
expertise and management authority to conduct independent oversight
and assure the implementation of the organization's quality system
relative to the ambient air quality monitoring program and should be
organizationally independent of environmental data generation
activities.
    2.3. Data Quality Performance Requirements.
    2.3.1 Data Quality Objectives. The DQOs, or the results of other
systematic planning processes, are statements that define the
appropriate type of data to collect and specify the tolerable levels
of potential decision errors that will be used as a basis for
establishing the quality and quantity of data needed to support the
monitoring objectives (reference 5 of this appendix). The DQOs will
be developed by the EPA to support the primary regulatory objectives
for each criteria pollutant. As they are developed, they will be
added to the regulation. The quality of the conclusions derived from
data interpretation can be affected by population uncertainty
(spatial or temporal uncertainty) and measurement uncertainty
(uncertainty associated with collecting, analyzing, reducing and
reporting concentration data). This appendix focuses on assessing
and controlling measurement uncertainty.
    <IP_ADDRESS> Measurement Uncertainty for Automated and Manual
PM2.5 Methods. The goal for acceptable measurement
uncertainty is defined for precision as an upper 90

percent confidence limit for the coefficient of variation (CV) of 10
percent and 10 percent for total bias.
    <IP_ADDRESS> Measurement Uncertainty for Automated O3
Methods. The goal for acceptable measurement uncertainty is defined
for precision as an upper 90 percent confidence limit for the CV of
7 percent and for bias as an upper 95 percent confidence limit for
the absolute bias of 7 percent.
    <IP_ADDRESS> Measurement Uncertainty for Pb Methods. The goal for
acceptable measurement uncertainty is defined for precision as an
upper 90 percent confidence limit for the CV of 20 percent and for
bias as an upper 95 percent confidence limit for the absolute bias
of 15 percent.
    <IP_ADDRESS> Measurement Uncertainty for NO2. The goal for
acceptable measurement uncertainty is defined for precision as an
upper 90 percent confidence limit for the CV of 15 percent and for
bias as an upper 95 percent confidence limit for the absolute bias
of 15 percent.
    <IP_ADDRESS> Measurement Uncertainty for SO2. The goal for
acceptable measurement uncertainty for precision is defined as an
upper 90 percent confidence limit for the CV of 10 percent and for
bias as an upper 95 percent confidence limit for the absolute bias
of 10 percent.
    2.4 National Performance Evaluation Programs. The PQAO shall
provide for the implementation of a program of independent and
adequate audits of all monitors providing data for NAAQS compliance
purposes including the provision of adequate resources for such
audit programs. A monitoring plan (or QAPP) which provides for PQAO
participation in the EPA's National Performance Audit Program
(NPAP), the PM2.5 Performance Evaluation Program
(PM2.5-PEP) program and the Pb Performance Evaluation
Program (Pb-PEP) and indicates the consent of the PQAO for the EPA
to apply an appropriate portion of the grant funds, which the EPA
would otherwise award to the PQAO for these QA activities, will be
deemed by the EPA to meet this requirement. For clarification and to
participate, PQAOs should contact either the appropriate EPA
regional quality assurance (QA) coordinator at the appropriate EPA
Regional Office location, or the NPAP coordinator at the EPA Air
Quality Assessment Division, Office of Air Quality Planning and
Standards, in Research Triangle Park, North Carolina. The PQAOs that
plan to implement these programs (self-implement) rather than use
the federal programs must meet the adequacy requirements found in
the appropriate sections that follow, as well as meet the definition
of independent assessment that follows.
    2.4.1 Independent assessment. An assessment performed by a
qualified individual, group, or organization that is not part of the
organization directly performing and accountable for the work being
assessed. This auditing organization must not be involved with the
generation of the ambient air monitoring data. An organization can
conduct the performance evaluation (PE) if it can meet this
definition and has a management structure that, at a minimum, will
allow for the separation of its routine sampling personnel from its
auditing personnel by two levels of management. In addition, the
sample analysis of audit filters must be performed by a laboratory
facility and laboratory equipment separate from the facilities used
for routine sample analysis. Field and laboratory personnel will be
required to meet PE field and laboratory training and certification
requirements to establish comparability to federally implemented
programs.
    2.5 Technical Systems Audit Program. Technical systems audits of
each PQAO shall be conducted at least every 3 years by the
appropriate EPA Regional Office and reported to the AQS. If a PQAO
is made up of more than one monitoring organization, all monitoring
organizations in the PQAO should be audited within 6 years (two TSA
cycles of the PQAO). As an example, if a state has five local
monitoring organizations that are consolidated under one PQAO, all
five local monitoring organizations should receive a technical
systems audit within a 6-year period. Systems audit programs are
described in reference 10 of this appendix.
    2.6 Gaseous and Flow Rate Audit Standards.
    2.6.1 Gaseous pollutant concentration standards (permeation
devices or cylinders of compressed gas) used to obtain test
concentrations for CO, SO2, NO, and NO2 must
be traceable to either a National Institute of Standards and
Technology (NIST) Traceable Reference Material (NTRM) or a NIST-
certified Gas Manufacturer's Internal Standard (GMIS), certified in
accordance with one of the procedures given in reference 4 of this
appendix. Vendors advertising certification with the procedures
provided in reference 4 of this appendix and distributing gases as
``EPA Protocol Gas'' for ambient air monitoring purposes must
participate in the EPA Ambient Air Protocol Gas Verification Program
or not use ``EPA'' in any form of advertising. Monitoring
organizations must provide information to the EPA on the gas
producers they use on an annual basis and those PQAOs purchasing
standards will be obligated, at the request of the EPA, to
participate in the program at least once every 5 years by sending a
new unused standard to a designated verification laboratory.
    2.6.2 Test concentrations for O3 must be obtained in
accordance with the ultraviolet photometric calibration procedure
specified in appendix D to Part 50 of this chapter and by means of a
certified NIST-traceable O3 transfer standard. Consult
references 7 and 8 of this appendix for guidance on transfer
standards for O3.
    2.6.3 Flow rate measurements must be made by a flow measuring
instrument that is NIST-traceable to an authoritative volume or
other applicable standard. Guidance for certifying some types of
flowmeters is provided in reference 10 of this appendix.
    2.7 Primary Requirements and Guidance. Requirements and guidance
documents for developing the quality system are contained in
references 1 through 11 of this appendix, which also contain many
suggested procedures, checks, and control specifications. Reference
10 describes specific guidance for the development of a quality
system for data collected for comparison to the NAAQS. Many specific
quality control checks and specifications for methods are included
in the respective reference methods described in Part 50 of this
chapter or in the respective equivalent method descriptions
available from the EPA (reference 6 of this appendix). Similarly,
quality control procedures related to specifically designated
reference and equivalent method monitors are contained in the
respective operation or instruction manuals associated with those
monitors.

3. Measurement Quality Check Requirements

    This section provides the requirements for PQAOs to perform the
measurement quality checks that can be used to assess data quality.
Data from these checks are required to be submitted to the AQS
within the same time frame as routinely-collected ambient
concentration data as described in 40 CFR 58.16. Table A-1 of this
appendix provides a summary of the types and frequency of the
measurement quality checks that will be described in this section.
    3.1. Gaseous Monitors of SO2, NO2,
O3, and CO.
    3.1.1 One-Point Quality Control (QC) Check for SO2,
NO2, O3, and CO. (a) A one-point QC check must
be performed at least once every 2 weeks on each automated monitor
used to measure SO2, NO2, O3 and
CO. With the advent of automated calibration systems, more frequent
checking is strongly encouraged. See Reference 10 of this appendix
for guidance on the review procedure. The QC check is made by
challenging the monitor with a QC check gas of known concentration
(effective concentration for open path monitors) between the
prescribed range of 0.005 and 0.08 parts per million (ppm) for
SO2, NO2, and O3, and between the
prescribed range of 0.5 and 5 ppm for CO monitors. The QC check gas
concentration selected within the prescribed range should be related
to the monitoring objectives for the monitor. If monitoring at an
NCore site or for trace level monitoring, the QC check concentration
should be selected to represent the mean or median concentrations at
the site. If the mean or median concentrations at trace gas sites
are below the MDL of the instrument the agency can select the lowest
concentration in the prescribed range that can be practically
achieved. If the mean or median concentrations at trace gas sites
are above the prescribed range the agency can select the highest
concentration in the prescribed range. An additional QC check point
is encouraged for those organizations that may have occasional high
values or would like to confirm the monitors' linearity at the
higher end of the operational range or around NAAQS concentrations.
If monitoring for NAAQS decisions, the QC concentration can be
selected at a higher concentration within the prescribed range but
should also consider precision points around mean or median monitor
concentrations.
    (b) Point analyzers must operate in their normal sampling mode
during the QC 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. The QC check

must be conducted before any calibration or adjustment to the
monitor.
    (c) Open path monitors are tested by inserting a test cell
containing a QC 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 QC check gas in the test cell must be selected to produce an
effective concentration in the range specified earlier in this
section. Generally, the QC test concentration measurement will be
the sum of the atmospheric pollutant concentration and the QC test
concentration. As such, 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 QC test from the QC
check gas 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 monitors should be tested
during periods when the atmospheric pollutant concentrations are
relatively low and steady.
    (d) Report the audit concentration of the QC gas and the
corresponding measured concentration indicated by the monitor to
AQS. The percent differences between these concentrations are used
to assess the precision and bias of the monitoring data as described
in sections 4.1.2 (precision) and 4.1.3 (bias) of this appendix.
    3.1.2 Annual performance evaluation for SO2, NO2, O3, or CO. A
performance evaluation must be conducted on each primary monitor
once a year. This can be accomplished by evaluating 25 percent of
the primary monitors each quarter. The evaluation should be
conducted by a trained experienced technician other than the routine
site operator.
    <IP_ADDRESS> The evaluation is made by challenging the monitor with
audit gas standards of known concentration from at least three audit
levels. One point must be within two to three times the method
detection limit of the instruments within the PQAOs network, the
second point will be less than or equal to the 99th percentile of
the data at the site or the network of sites in the PQAO or the next
highest audit concentration level. The third point can be around the
primary NAAQS or the highest 3-year concentration at the site or the
network of sites in the PQAO. An additional 4th level is encouraged
for those agencies that would like to confirm the monitors'
linearity at the higher end of the operational range. In rare
circumstances, there may be sites measuring concentrations above
audit level 10. Notify the appropriate EPA region and the AQS
program in order to make accommodations for auditing at levels above
level 10.

----------------------------------------------------------------------------------------------------------------
                                                                     Concentration Range, ppm
                   Audit level                   ---------------------------------------------------------------
                                                        O3              SO2             NO2             CO
----------------------------------------------------------------------------------------------------------------
1...............................................    0.004-0.0059   0.0003-0.0029   0.0003-0.0029     0.020-0.059
2...............................................     0.006-0.019   0.0030-0.0049   0.0030-0.0049     0.060-0.199
3...............................................     0.020-0.039   0.0050-0.0079   0.0050-0.0079     0.200-0.899
4...............................................     0.040-0.069   0.0080-0.0199   0.0080-0.0199     0.900-2.999
5...............................................     0.070-0.089   0.0200-0.0499   0.0200-0.0499     3.000-7.999
6...............................................     0.090-0.119   0.0500-0.0999   0.0500-0.0999    8.000-15.999
7...............................................     0.120-0.139   0.1000-0.1499   0.1000-0.2999   16.000-30.999
8...............................................     0.140-0.169   0.1500-0.2599   0.3000-0.4999   31.000-39.999
9...............................................     0.170-0.189   0.2600-0.7999   0.5000-0.7999   40.000-49.999
10..............................................     0.190-0.259    0.8000-1.000    0.8000-1.000   50.000-60.000
----------------------------------------------------------------------------------------------------------------

    <IP_ADDRESS> The NO2 audit techniques may vary depending
on the ambient monitoring method. For chemiluminescence-type
NO2 analyzers, gas phase titration (GPT) techniques
should be based on EPA guidance documents and monitoring agency
experience. The NO2 gas standards may be more appropriate
than GPT for direct NO2 methods that do not employ
converters. Care should be taken to ensure the stability of such gas
standards prior to use.
    <IP_ADDRESS> The standards from which audit gas test concentrations
are obtained must meet the specifications of section 2.6.1 of this
appendix. The gas standards and equipment used for the performance
evaluation must not be the same as the standards and equipment used
for one-point QC, calibrations, span evaluations or NPAP.
    <IP_ADDRESS> For point analyzers, the evaluation shall be carried out
by allowing the monitor to analyze the audit gas test atmosphere in
its normal sampling mode such that the test atmosphere passes
through all filters, scrubbers, conditioners, and other sample inlet
components used during normal ambient sampling and as much of the
ambient air inlet system as is practicable.
    <IP_ADDRESS> Open-path monitors are evaluated by inserting a test
cell containing the various audit gas concentrations 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 evaluation, and the normal
monitoring configuration of the instrument should be modified as
little as possible to accommodate the test cell for the evaluation.
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
evaluation level ranges specified in this section of this appendix.
Generally, each evaluation concentration measurement result will be
the sum of the atmospheric pollutant concentration and the
evaluation test concentration. As such, 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 evaluation
test (or preferably before and after each evaluation concentration
level) from the evaluation concentration measurement. If the
difference between the before and after measurements is greater than
20 percent of the effective concentration of the test gas standard,
discard the test result for that concentration level and repeat the
test for that level. If possible, open path monitors should be
evaluated during periods when the atmospheric pollutant
concentrations are relatively low and steady. Also, if the open-path
instrument is not installed in a permanent manner, the monitoring
path length must be reverified to be within 3 percent to
validate the evaluation since the monitoring path length is critical
to the determination of the effective concentration.
    <IP_ADDRESS> Report both the evaluation concentrations (effective
concentrations for open-path monitors) of the audit gases and the
corresponding measured concentration (corrected concentrations, if
applicable, for open path monitors) indicated or produced by the
monitor being tested to AQS. The percent differences between these
concentrations are used to assess the quality of the monitoring data
as described in section 4.1.1 of this appendix.
    3.1.3 National Performance Audit Program (NPAP).
    The NPAP is a performance evaluation which is a type of audit
where quantitative data are collected independently in order to
evaluate the proficiency of an analyst, monitoring instrument or
laboratory. Due to the implementation approach used in the

program, NPAP provides a national independent assessment of
performance while maintaining a consistent level of data quality.
Details of the program can be found in reference 11 of this
appendix. The program requirements include:
    <IP_ADDRESS> Performing audits of the primary monitors at 20 percent
of monitoring sites per year, and 100 percent of the sites every 6
years. High-priority sites may be audited more frequently. Since not
all gaseous criteria pollutants are monitored at every site within a
PQAO, it is not required that 20 percent of the primary monitors for
each pollutant receive an NPAP audit each year only that 20 percent
of the PQAOs monitoring sites receive an NPAP audit. It is expected
that over the 6-year period all primary monitors for all gaseous
pollutants will receive an NPAP audit.
    <IP_ADDRESS> Developing a delivery system that will allow for the
audit concentration gasses to be introduced to the probe inlet where
logistically feasible.
    <IP_ADDRESS> Using audit gases that are verified against the NIST
standard reference methods or special review procedures and
validated annually for CO, SO2 and NO2, and at
the beginning of each quarter of audits for O3.
    <IP_ADDRESS> As described in section 2.4 of this appendix, the PQAO
may elect, on an annual basis, to utilize the federally implemented
NPAP program. If the PQAO plans to self-implement NPAP, the EPA will
establish training and other technical requirements for PQAOs to
establish comparability to federally implemented programs. In
addition to meeting the requirements in sections <IP_ADDRESS> through
<IP_ADDRESS> of this appendix, the PQAO must:
    (a) Utilize an audit system equivalent to the federally
implemented NPAP audit system and is separate from equipment used in
annual performance evaluations.
    (b) Perform a whole system check by having the NPAP system
tested against an independent and qualified EPA lab, or equivalent.
    (c) Evaluate the system with the EPA NPAP program through
collocated auditing at an acceptable number of sites each year (at
least one for an agency network of five or less sites; at least two
for a network with more than five sites).
    (d) Incorporate the NPAP in the PQAO's quality assurance project
plan.
    (e) Be subject to review by independent, EPA-trained personnel.
    (f) Participate in initial and update training/certification
sessions.
    <IP_ADDRESS> OAQPS, in consultation with the relevant EPA Regional
Office, may approve the PQAO's plan to self-implement NPAP if the
OAQPS determines that the PQAO's self-implementation plan is
equivalent to the federal programs and adequate to meet the
objectives of national consistency and data quality.
    3.2 PM2.5.
    3.2.1 Flow Rate Verification for PM2.5. A one-point flow rate
verification check must be performed at least once every month (each
verification minimally separated by 14 days) on each monitor used to
measure PM2.5. The verification is made by checking the
operational flow rate of the monitor. If the verification is made in
conjunction with a flow rate adjustment, it must be made prior to
such flow rate adjustment. For the standard procedure, use a flow
rate transfer standard certified in accordance with section 2.6 of
this appendix to check the monitor's normal flow rate. Care should
be used in selecting and using the flow rate measurement device such
that it does not alter the normal operating flow rate of the
monitor. Report the flow rate of the transfer standard and the
corresponding flow rate measured by the monitor to AQS. The percent
differences between the audit and measured flow rates are used to
assess the bias of the monitoring data as described in section 4.2.2
of this appendix (using flow rates in lieu of concentrations).
    3.2.2 Semi-Annual Flow Rate Audit for PM2.5. Audit the flow rate
of the particulate monitor twice a year. The two audits should
ideally be spaced between 5 and 7 months apart. The EPA strongly
encourages more frequent auditing. The audit should (preferably) be
conducted by a trained experienced technician other than the routine
site operator. The audit is made by measuring the monitor's normal
operating flow rate(s) using a flow rate transfer standard certified
in accordance with section 2.6 of this appendix. The flow rate
standard used for auditing must not be the same flow rate standard
used for verifications or to calibrate the monitor. However, both
the calibration standard and the audit standard may be referenced to
the same primary flow rate or volume standard. Care must be taken in
auditing the flow rate to be certain that the flow measurement
device does not alter the normal operating flow rate of the monitor.
Report the audit flow rate of the transfer standard and the
corresponding flow rate measured by the monitor to AQS. The percent
differences between these flow rates are used to evaluate monitor
performance.
    3.2.3 Collocated Quality Control Sampling Procedures for PM2.5.
For each pair of collocated monitors, designate one sampler as the
primary monitor whose concentrations will be used to report air
quality for the site, and designate the other as the quality control
monitor. There can be only one primary monitor at a monitoring site
for a given time period.
    <IP_ADDRESS> For each distinct monitoring method designation (FRM or
FEM) that a PQAO is using for a primary monitor, the PQAO must have
15 percent of the primary monitors of each method designation
collocated (values of 0.5 and greater round up); and have at least
one collocated quality control monitor (if the total number of
monitors is less than three). The first collocated monitor must be a
designated FRM monitor.
    <IP_ADDRESS> In addition, monitors selected for collocation must also
meet the following requirements:
    (a) A primary monitor designated as an EPA FRM shall be
collocated with a quality control monitor having the same EPA FRM
method designation.
    (b) For each primary monitor designated as an EPA FEM used by
the PQAO, 50 percent of the monitors designated for collocation, or
the first if only one collocation is necessary, shall be collocated
with a FRM quality control monitor and 50 percent of the monitors
shall be collocated with a monitor having the same method
designation as the FEM primary monitor. If an odd number of
collocated monitors is required, the additional monitor shall be a
FRM quality control monitor. An example of the distribution of
collocated monitors for each unique FEM is provided below. Table A-2
of this appendix demonstrates the collocation procedure with a PQAO
having one type of primary FRM and multiple primary FEMs.

----------------------------------------------------------------------------------------------------------------
                                                                                #Collocated
                                                                                #Collocated      with same
          #Primary FEMS of a unique method designation              #Collocated     with an FRM       method
                                                                                designation
----------------------------------------------------------------------------------------------------------------
1-9.............................................................               1               1               0
10-16...........................................................               2               1               1
17-23...........................................................               3               2               1
24-29...........................................................               4               2               2
30-36...........................................................               5               3               2
37-43...........................................................               6               3               3
----------------------------------------------------------------------------------------------------------------

    <IP_ADDRESS> Since the collocation requirements are used to assess
precision of the primary monitors and there can only be one primary
monitor at a monitoring site, a site can only count for the
collocation of the method designation of the primary monitor at that
site.
    <IP_ADDRESS> The collocated monitors should be deployed according to
the following protocol:
    (a) Fifty percent of the collocated quality control monitors
should be deployed at sites with annual average or daily
concentrations estimated to be within plus or minus 20 percent of
either the annual or 24-hour NAAQS and the remainder at the PQAOs
discretion;

    (b) If an organization has no sites with annual average or daily
concentrations within 20 percent of the annual NAAQS or
24-hour NAAQS, 50 percent of the collocated quality control monitors
should be deployed at those sites with the annual mean
concentrations or 24-hour concentrations among the highest for all
sites in the network and the remainder at the PQAOs discretion.
    (c) The two collocated monitors must be within 4 meters (inlet
to inlet) of each other and at least 2 meters apart for flow rates
greater than 200 liters/min or at least 1 meter apart for samplers
having flow rates less than 200 liters/min to preclude airflow
interference. A waiver allowing up to 10 meters horizontal distance
and up to 3 meters vertical distance (inlet to inlet) between a
primary and collocated sampler may be approved by the Regional
Administrator for sites at a neighborhood or larger scale of
representation during the annual network plan approval process.
Sampling and analytical methodologies must be the consistently
implemented for both primary and collocated quality control samplers
and for all other samplers in the network.
    (d) Sample the collocated quality control monitor on a 1-in-12
day schedule. Report the measurements from both primary and
collocated quality control monitors at each collocated sampling site
to AQS. The calculations for evaluating precision between the two
collocated monitors are described in section 4.2.1 of this appendix.
    3.2.4 PM2.5 Performance Evaluation Program (PEP) Procedures. The
PEP is an independent assessment used to estimate total measurement
system bias. These evaluations will be performed under the NPEP as
described in section 2.4 of this appendix or a comparable program.
Performance evaluations will be performed annually within each PQAO.
For PQAOs with less than or equal to five monitoring sites, five
valid performance evaluation audits must be collected and reported
each year. For PQAOs with greater than five monitoring sites, eight
valid performance evaluation audits must be collected and reported
each year. A valid performance evaluation audit means that both the
primary monitor and PEP audit concentrations are valid and above 3
[micro]g/m\3\. Siting of the PEP monitor must be consistent with
section <IP_ADDRESS>(c). However, any horizontal distance greater than 4
meters and any vertical distance greater than one meter must be
reported to the EPA regional PEP coordinator. Additionally for every
monitor designated as a primary monitor, a primary quality assurance
organization must:
    <IP_ADDRESS> Have each method designation evaluated each year; and,
    <IP_ADDRESS> Have all FRM, FEM or ARM samplers subject to a PEP audit
at least once every 6 years, which equates to approximately 15
percent of the monitoring sites audited each year.
    <IP_ADDRESS>. Additional information concerning the PEP is contained
in reference 10 of this appendix. The calculations for evaluating
bias between the primary monitor and the performance evaluation
monitor for PM2.5 are described in section 4.2.5 of this
appendix.
    3.3PM10.
    3.3.1 Flow Rate Verification for PM10 Low Volume Samplers (less
than 200 liter/minute). A one-point flow rate verification check
must be performed at least once every month (each verification
minimally separated by 14 days) on each monitor used to measure
PM10. The verification is made by checking the
operational flow rate of the monitor. If the verification is made in
conjunction with a flow rate adjustment, it must be made prior to
such flow rate adjustment. For the standard procedure, use a flow
rate transfer standard certified in accordance with section 2.6 of
this appendix to check the monitor's normal flow rate. Care should
be taken in selecting and using the flow rate measurement device
such that it does not alter the normal operating flow rate of the
monitor. The percent differences between the audit and measured flow
rates are reported to AQS and used to assess the bias of the
monitoring data as described in section 4.2.2 of this appendix
(using flow rates in lieu of concentrations).
    3.3.2 Flow Rate Verification for PM10 High Volume Samplers
(greater than 200 liters/minute). For PM10 high volume
samplers, the verification frequency is one verification every 90
days (quarter) with 4 in a year. Other than verification frequency,
follow the same technical procedure as described in section 3.3.1 of
this appendix.
    3.3.3 Semi-Annual Flow Rate Audit for PM10. Audit the flow rate
of the particulate monitor twice a year. The two audits should
ideally be spaced between 5 and 7 months apart. The EPA strongly
encourages more frequent auditing. The audit should (preferably) be
conducted by a trained experienced technician other than the routine
site operator. The audit is made by measuring the monitor's normal
operating flow rate using a flow rate transfer standard certified in
accordance with section 2.6 of this appendix. The flow rate standard
used for auditing must not be the same flow rate standard used for
verifications or to calibrate the monitor. However, both the
calibration standard and the audit standard may be referenced to the
same primary flow rate or volume standard. Care must be taken in
auditing the flow rate to be certain that the flow measurement
device does not alter the normal operating flow rate of the monitor.
Report the audit flow rate of the transfer standard and the
corresponding flow rate measured by the monitor to AQS. The percent
differences between these flow rates are used to evaluate monitor
performance.
    3.3.4 Collocated Quality Control Sampling Procedures for Manual
PM10. Collocated sampling for PM10 is only required for
manual samplers. For each pair of collocated monitors, designate one
sampler as the primary monitor whose concentrations will be used to
report air quality for the site and designate the other as the
quality control monitor.
    <IP_ADDRESS> For manual PM10 samplers, a PQAO must:
    (a) Have 15 percent of the primary monitors collocated (values
of 0.5 and greater round up); and
    (b) Have at least one collocated quality control monitor (if the
total number of monitors is less than three).
    <IP_ADDRESS> The collocated quality control monitors should be
deployed according to the following protocol:
    (a) Fifty percent of the collocated quality control monitors
should be deployed at sites with daily concentrations estimated to
be within plus or minus 20 percent of the applicable NAAQS and the
remainder at the PQAOs discretion;
    (b) If an organization has no sites with daily concentrations
within plus or minus 20 percent of the NAAQS, 50 percent of the
collocated quality control monitors should be deployed at those
sites with the daily mean concentrations among the highest for all
sites in the network and the remainder at the PQAOs discretion.
    (c) The two collocated monitors must be within 4 meters (inlet
to inlet) of each other and at least 2 meters apart for flow rates
greater than 200 liters/min or at least 1 meter apart for samplers
having flow rates less than 200 liters/min to preclude airflow
interference. A waiver allowing up to 10 meters horizontal distance
and up to 3 meters vertical distance (inlet to inlet) between a
primary and collocated sampler may be approved by the Regional
Administrator for sites at a neighborhood or larger scale of
representation. This waiver may be approved during the annual
network plan approval process. Sampling and analytical methodologies
must be the consistently implemented for both collocated samplers
and for all other samplers in the network.
    (d) Sample the collocated quality control monitor on a 1-in-12
day schedule. Report the measurements from both primary and
collocated quality control monitors at each collocated sampling site
to AQS. The calculations for evaluating precision between the two
collocated monitors are described in section 4.2.1 of this appendix.
    (e) In determining the number of collocated quality control
sites required for PM10, monitoring networks for lead
(Pb-PM10) should be treated independently from networks
for particulate matter (PM), even though the separate networks may
share one or more common samplers. However, a single quality control
monitor that meets the collocation requirements for Pb-
PM10 and PM10 may serve as a collocated
quality control monitor for both networks. Extreme care must be
taken when using the filter from a quality control monitor for both
PM10 and Pb analysis. A PM10 filter weighing
should occur prior to any Pb analysis.
    3.4 Pb.
    3.4.1 Flow Rate Verification for Pb-PM10 Low Volume Samplers
(less than 200 liter/minute). A one-point flow rate verification
check must be performed at least once every month (each verification
minimally separated by 14 days) on each monitor used to measure Pb.
The verification is made by checking the operational flow rate of
the monitor. If the verification is made in conjunction with a flow
rate adjustment, it must be made prior to such flow rate adjustment.
For the standard procedure, use a flow rate transfer standard
certified in accordance with section 2.6 of this appendix to check
the monitor's normal flow rate. Care should be taken in selecting
and using the flow rate measurement device such that it does not

alter the normal operating flow rate of the monitor. The percent
differences between the audit and measured flow rates are reported
to AQS and used to assess the bias of the monitoring data as
described in section 4.2.2 of this appendix (using flow rates in
lieu of concentrations).
    3.4.2 Flow Rate Verification for Pb High Volume Samplers
(greater than 200 liters/minute). For high volume samplers, the
verification frequency is one verification every 90 days (quarter)
with four in a year. Other than verification frequency, follow the
same technical procedure as described in section 3.4.1 of this
appendix.
    3.4.3 Semi-Annual Flow Rate Audit for Pb. Audit the flow rate of
the particulate monitor twice a year. The two audits should ideally
be spaced between 5 and 7 months apart. The EPA strongly encourages
more frequent auditing. The audit should (preferably) be conducted
by a trained experienced technician other than the routine site
operator. The audit is made by measuring the monitor's normal
operating flow rate using a flow rate transfer standard certified in
accordance with section 2.6 of this appendix. The flow rate standard
used for auditing must not be the same flow rate standard used for
verifications or to calibrate the monitor. However, both the
calibration standard and the audit standard may be referenced to the
same primary flow rate or volume standard. Care must be taken in
auditing the flow rate to be certain that the flow measurement
device does not alter the normal operating flow rate of the monitor.
Report the audit flow rate of the transfer standard and the
corresponding flow rate measured by the monitor to AQS. The percent
differences between these flow rates are used to evaluate monitor
performance.
    3.4.4 Collocated Quality Control Sampling for TSP Pb for
monitoring sites other than non-source oriented NCore. For each pair
of collocated monitors for manual TSP Pb samplers, designate one
sampler as the primary monitor whose concentrations will be used to
report air quality for the site, and designate the other as the
quality control monitor.
    <IP_ADDRESS> A PQAO must:
    (a) Have 15 percent of the primary monitors (not counting non-
source oriented NCore sites in PQAO) collocated. Values of 0.5 and
greater round up; and
    (b) Have at least one collocated quality control monitor (if the
total number of monitors is less than three).
    <IP_ADDRESS> The collocated quality control monitors should be
deployed according to the following protocol:
    (a) The first collocated Pb site selected must be the site
measuring the highest Pb concentrations in the network. If the site
is impractical, alternative sites, approved by the EPA Regional
Administrator, may be selected. If additional collocated sites are
necessary, collocated sites may be chosen that reflect average
ambient air Pb concentrations in the network.
    (b) The two collocated monitors must be within 4 meters (inlet
to inlet) of each other and at least 2 meters apart for flow rates
greater than 200 liters/min or at least 1 meter apart for samplers
having flow rates less than 200 liters/min to preclude airflow
interference.
    (c) Sample the collocated quality control monitor on a 1-in-12
day schedule. Report the measurements from both primary and
collocated quality control monitors at each collocated sampling site
to AQS. The calculations for evaluating precision between the two
collocated monitors are described in section 4.2.1 of this appendix.
    3.4.5 Collocated Quality Control Sampling for Pb-PM10
at monitoring sites other than non-source oriented NCore. If a PQAO
is monitoring for Pb-PM10 at sites other than at a non-
source oriented NCore site then the PQAO must:
    <IP_ADDRESS> Have 15 percent of the primary monitors (not counting
non-source oriented NCore sites in PQAO) collocated. Values of 0.5
and greater round up; and
    <IP_ADDRESS> Have at least one collocated quality control monitor (if
the total number of monitors is less than three).
    <IP_ADDRESS> The collocated monitors should be deployed according to
the following protocol:
    (a) Fifty percent of the collocated quality control monitors
should be deployed at sites with the highest 3-month average
concentrations and the remainder at the PQAOs discretion.
    (b) The two collocated monitors must be within 4 meters (inlet
to inlet) of each other and at least 2 meters apart for flow rates
greater than 200 liters/min or at least 1 meter apart for samplers
having flow rates less than 200 liters/min to preclude airflow
interference. A waiver allowing up to 10 meters horizontal distance
and up to 3 meters vertical distance (inlet to inlet) between a
primary and collocated sampler may be approved by the Regional
Administrator for sites at a neighborhood or larger scale of
representation. This waiver may be approved during the annual
network plan approval process. Sampling and analytical methodologies
must be the consistently implemented for both collocated samplers
and for all other samplers in the network.
    (c) Sample the collocated quality control monitor on a 1-in-12
day schedule. Report the measurements from both primary and
collocated quality control monitors at each collocated sampling site
to AQS. The calculations for evaluating precision between the two
collocated monitors are described in section 4.2.1 of this appendix.
    (d) In determining the number of collocated quality control
sites required for Pb-PM10, monitoring networks for
PM10 should be treated independently from networks for
Pb-PM10, even though the separate networks may share one
or more common samplers. However, a single quality control monitor
that meets the collocation requirements for Pb-PM10 and
PM10 may serve as a collocated quality control monitor
for both networks. Extreme care must be taken when using a using the
filter from a quality control monitor for both PM10 and
Pb analysis. A PM10 filter weighing should occur prior to
any Pb analysis.
    3.4.6 Pb Analysis Audits. Each calendar quarter, audit the Pb
reference or equivalent method analytical procedure using filters
containing a known quantity of Pb. These audit filters are prepared
by depositing a Pb standard on unexposed filters and allowing them
to dry thoroughly. The audit samples must be prepared using batches
of reagents different from those used to calibrate the Pb analytical
equipment being audited. Prepare audit samples in the following
concentration ranges:

------------------------------------------------------------------------
                                   Equivalent ambient Pb concentration,
              Range                             [mu]g/m \3\
------------------------------------------------------------------------
1...............................  30-100% of Pb NAAQS.
2...............................  200-300% of Pb NAAQS.
------------------------------------------------------------------------

    (a) Extract the audit samples using the same extraction
procedure used for exposed filters.
    (b) Analyze three audit samples in each of the two ranges each
quarter samples are analyzed. The audit sample analyses shall be
distributed as much as possible over the entire calendar quarter.
    (c) Report the audit concentrations (in [mu]g Pb/filter or
strip) and the corresponding measured concentrations (in [mu]g Pb/
filter or strip) to AQS using AQS unit code 077. The percent
differences between the concentrations are used to calculate
analytical accuracy as described in section 4.2.6 of this appendix.
    3.4.7 Pb PEP Procedures for monitoring sites other than non-
source oriented NCore. The PEP is an independent assessment used to
estimate total measurement system bias. These evaluations will be
performed under the NPEP described in section 2.4 of this appendix
or a comparable program. Each year, one performance evaluation audit
must be performed at one Pb site in each primary quality assurance
organization that has less than or equal to five sites and two
audits at PQAOs with greater than five sites. Non-source oriented
NCore sites are not counted. Siting of the PEP monitor must be
consistent with section <IP_ADDRESS>(b). However, any horizontal distance
greater than 4 meters and any vertical distance greater than 1 meter
must be reported to the EPA regional PEP coordinator. In addition,
each year, four collocated samples from PQAOs with less than or
equal to five sites and six collocated samples at PQAOs with greater
than five sites must be sent to an independent laboratory, the same
laboratory as the performance evaluation audit, for analysis. The
calculations for evaluating bias between the primary monitor and the
performance evaluation monitor for Pb are described in section 4.2.4
of this appendix.

4. Calculations for Data Quality Assessments

    (a) Calculations of measurement uncertainty are carried out by
the EPA according to the following procedures. The PQAOs must report
the data to AQS for all measurement quality checks as specified in
this appendix even though they may elect to perform some or all of
the calculations in this section on their own.
    (b) The EPA will provide annual assessments of data quality
aggregated by site and PQAO for SO2, NO2,
O3 and CO and by PQAO for PM10,
PM2.5, and Pb.
    (c) At low concentrations, agreement between the measurements of
collocated quality control samplers, expressed as

relative percent difference or percent difference, may be relatively
poor. For this reason, collocated measurement pairs are selected for
use in the precision and bias calculations only when both
measurements are equal to or above the following limits:
    (1) Pb: 0.002 [micro]g/m\3\ (Methods approved after 3/04/2010,
with exception of manual equivalent method EQLA-0813-803).
    (2) Pb: 0.02 [micro]g/m\3\ (Methods approved before 3/04/2010,
and manual equivalent method EQLA-0813-803).
    (3) PM10 (Hi-Vol): 15 [micro]g/m\3\.
    (4) PM10 (Lo-Vol): 3 [micro]g/m\3\.
    (5) PM2.5: 3 [micro]g/m\3\.
    4.1 Statistics for the Assessment of QC Checks for
SO2, NO2, O3 and CO.
    4.1.1 Percent Difference. Many of the measurement quality checks
start with a comparison of an audit concentration or value (flow
rate) to the concentration/value measured by the monitor and use
percent difference as the comparison statistic as described in
equation 1 of this section. For each single point check, calculate
the percent difference, di, as follows:
[GRAPHIC] [TIFF OMITTED] TR28MR16.000

where meas is the concentration indicated by the PQAO's instrument
and audit is the audit concentration of the standard used in the QC
check being measured.
    4.1.2 Precision Estimate. The precision estimate is used to
assess the one-point QC checks for SO2, NO2,
O3, or CO described in section 3.1.1 of this appendix.
The precision estimator is the coefficient of variation upper bound
and is calculated using equation 2 of this section:
[GRAPHIC] [TIFF OMITTED] TR28MR16.001

where n is the number of single point checks being aggregated; X\2\
0.1,n-1 is the 10th percentile of a chi-squared
distribution with n-1 degrees of freedom.
    4.1.3 Bias Estimate. The bias estimate is calculated using the
one-point QC checks for SO2, NO2,
O3, or CO described in section 3.1.1 of this appendix.
The bias estimator is an upper bound on the mean absolute value of
the percent differences as described in equation 3 of this section:
[GRAPHIC] [TIFF OMITTED] TR28MR16.002

where n is the number of single point checks being aggregated;
t0.95,n-1 is the 95th quantile of a t-distribution with
n-1 degrees of freedom; the quantity AB is the mean of the absolute
values of the d i ' s and is calculated using equation 4
of this section:
[GRAPHIC] [TIFF OMITTED] TR28MR16.003

and the quantity AS is the standard deviation of the absolute value
of the di ' s and is calculated using equation 5 of this
section:
[GRAPHIC] [TIFF OMITTED] TR28MR16.004

    <IP_ADDRESS> Assigning a sign (positive/negative) to the bias
estimate. Since the bias statistic as calculated in equation 3 of
this appendix uses absolute values, it does not have a tendency
(negative or positive bias) associated with it. A sign will be
designated by rank ordering the percent differences of the QC check
samples from a given site for a particular assessment interval.
    <IP_ADDRESS> Calculate the 25th and 75th percentiles of the percent
differences for each site. The absolute bias upper bound should be
flagged as positive if both percentiles are positive and negative if
both percentiles are negative. The absolute bias upper bound would
not be flagged if the 25th and 75th percentiles are of different
signs.
    4.2 Statistics for the Assessment of PM10,
PM2.5, and Pb.
4.2.1 Collocated Quality Control Sampler Precision Estimate for
PM10, PM2.5 and Pb. Precision is estimated via duplicate
measurements from collocated samplers. It is recommended that the
precision be aggregated at the PQAO level quarterly, annually, and
at the 3-year level. The data pair would only be considered valid if
both concentrations are greater than or equal to the minimum values
specified in section 4(c) of this appendix. For each collocated data
pair, calculate the relative percent difference, di,
using equation 6 of this appendix:
[GRAPHIC] [TIFF OMITTED] TR28MR16.005

where Xi is the concentration from the primary sampler
and Yi is the concentration value from the audit sampler.
The coefficient of variation upper bound is calculated using
equation 7 of this appendix:

[GRAPHIC] [TIFF OMITTED] TR28MR16.006

where n is the number of valid data pairs being aggregated, and X\2\
0.1,n-1 is the 10th percentile of a chi-squared
distribution with n-1 degrees of freedom. The factor of 2 in the
denominator adjusts for the fact that each di is
calculated from two values with error.
    4.2.2 One-Point Flow Rate Verification Bias Estimate for PM10,
PM2.5 and Pb. For each one-point flow rate verification, calculate
the percent difference in volume using equation 1 of this appendix
where meas is the value indicated by the sampler's volume
measurement and audit is the actual volume indicated by the auditing
flow meter. The absolute volume bias upper bound is then calculated
using equation 3, where n is the number of flow rate audits being
aggregated; t0.95,n-1 is the 95th quantile of a t-
distribution with n-1 degrees of freedom, the quantity AB is the
mean of the absolute values of the di's and is calculated
using equation 4 of this appendix, and the quantity AS in equation 3
of this appendix is the standard deviation of the absolute values if
the di's and is calculated using equation 5 of this
appendix.
    4.2.3 Semi-Annual Flow Rate Audit Bias Estimate for PM10, PM2.5
and Pb. Use the same procedure described in section 4.2.2 for the
evaluation of flow rate audits.
    4.2.4 Performance Evaluation Programs Bias Estimate for Pb. The
Pb bias estimate is calculated using the paired routine and the PEP
monitor as described in section 3.4.7. Use the same procedures as
described in section 4.1.3 of this appendix.
    4.2.5 Performance Evaluation Programs Bias Estimate for PM2.5.
The bias estimate is calculated using the PEP audits described in
section 4.1.3 of this appendix. The bias estimator is based on the
mean percent differences (Equation 1). The mean percent difference,
D, is calculated by Equation 8 below.
[GRAPHIC] [TIFF OMITTED] TR28MR16.007

where nj is the number of pairs and
d1,d2,...dnj are the biases for
each pair to be averaged.
    4.2.6 Pb Analysis Audit Bias Estimate. The bias estimate is
calculated using the analysis audit data described in section 3.4.6.
Use the same bias estimate procedure as described in section 4.1.3
of this appendix.

5. Reporting Requirements

    5.1 Reporting Requirements. For each pollutant, prepare a list
of all monitoring sites and their AQS site identification codes in
each PQAO and submit the list to the appropriate EPA Regional
Office, with a copy to AQS. Whenever there is a change in this list
of monitoring sites in a PQAO, report this change to the EPA
Regional Office and to AQS.
    5.1.1 Quarterly Reports. For each quarter, each PQAO shall
report to AQS directly (or via the appropriate EPA Regional Office
for organizations not direct users of AQS) the results of all valid
measurement quality checks it has carried out during the quarter.
The quarterly reports must be submitted consistent with the data
reporting requirements specified for air quality data as set forth
in 40 CFR 58.16. The EPA strongly encourages early submission of the
quality assurance data in order to assist the PQAOs ability to
control and evaluate the quality of the ambient air data.
    5.1.2 Annual Reports.
    <IP_ADDRESS> When the PQAO has certified relevant data for the
calendar year, the EPA will calculate and report the measurement
uncertainty for the entire calendar year.

6. References

    (1) American National Standard--Specifications and Guidelines
for Quality Systems for Environmental Data Collection and
Environmental Technology Programs. ANSI/ASQC E4-2014. February 2014.
Available from American Society for Quality Control, 611 East
Wisconsin Avenue, Milwaukee, WI 53202.
    (2) EPA Requirements for Quality Management Plans. EPA QA/R-2.
EPA/240/B-01/002. March 2001, Reissue May 2006. Office of
Environmental Information, Washington DC 20460. http://www.epa.gov/quality/agency-wide-quality-system-documents.
    (3) EPA Requirements for Quality Assurance Project Plans for
Environmental Data Operations. EPA QA/R-5. EPA/240/B-01/003. March
2001, Reissue May 2006. Office of Environmental Information,
Washington DC 20460. http://www.epa.gov/quality/agency-wide-quality-system-documents.
    (4) EPA Traceability Protocol for Assay and Certification of
Gaseous Calibration Standards. EPA-600/R-12/531. May, 2012.
Available from U.S. Environmental Protection Agency, National Risk
Management Research Laboratory, Research Triangle Park NC 27711.
http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=245292.
    (5) Guidance for the Data Quality Objectives Process. EPA QA/G-
4. EPA/240/B-06/001. February, 2006. Office of Environmental
Information, Washington DC 20460. http://www.epa.gov/quality/agency-wide-quality-system-documents.
    (6) List of Designated Reference and Equivalent Methods.
Available from U.S. Environmental Protection Agency, National
Exposure Research Laboratory, Human Exposure and Atmospheric
Sciences Division, MD-D205-03, Research Triangle Park, NC 27711.
http://www3.epa.gov/ttn/amtic/criteria.html.
    (7) Transfer Standards for the Calibration of Ambient Air
Monitoring Analyzers for Ozone. EPA-454/B-13-004 U.S. Environmental
Protection Agency, Research Triangle Park, NC 27711, October, 2013.
http://www3.epa.gov/ttn/amtic/qapollutant.html.
    (8) 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. http://www.epa.gov/ttn/amtic/cpreldoc.html.
    (9) 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. http://www3.epa.gov/ttn/amtic/qalist.html.
    (10) Quality Assurance Handbook for Air Pollution Measurement
Systems, Volume II: Ambient Air Quality Monitoring Program Quality
System Development. EPA-454/B-13-003. http://www3.epa.gov/ttn/amtic/qalist.html.
    (11) National Performance Evaluation Program Standard Operating
Procedures. http://www3.epa.gov/ttn/amtic/npapsop.html.

                 Table A-1 of Appendix A to Part 58--Minimum Data Assessment Requirements for NAAQS Related Criteria Pollutant Monitors
--------------------------------------------------------------------------------------------------------------------------------------------------------
               Method                   Assessment method           Coverage           Minimum frequency     Parameters reported    AQS assessment type
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                           Gaseous Methods (CO, NO2, SO2, O3)
--------------------------------------------------------------------------------------------------------------------------------------------------------
One-Point QC for SO2, NO2, O3, CO..  Response check at       Each analyzer.........  Once per 2 weeks.....  Audit concentration    One-Point QC.
                                      concentration 0.005-                                                   \1\ and measured
                                      0.08 ppm SO2, NO2,                                                     concentration. \2\
                                      O3, and.
                                     0.5 and 5 ppm CO......
Annual performance evaluation for    See section 3.1.2 of    Each analyzer.........  Once per year........  Audit concentration    Annual PE.
 SO2, NO2, O3, CO.                    this appendix.                                                         \1\ and measured
                                                                                concentration \2\
                                                                                for each level.
NPAP for SO2, NO2, O3, CO..........  Independent Audit.....  20% of sites each year  Once per year........  Audit concentration    NPAP.
                                                                                \1\ and measured
                                                                                concentration \2\
                                                                                for each level.
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                   Particulate Methods
--------------------------------------------------------------------------------------------------------------------------------------------------------
Continuous \4\ method--collocated    Collocated samplers...  15%...................  1-in-12 days.........  Primary sampler        No Transaction
 quality control sampling PM2.5.                                                                             concentration and      reported as raw
                                                                                duplicate sampler      data.
                                                                                concentration. \3\
Manual method--collocated quality    Collocated samplers...  15%...................  1-in-12 days.........  Primary sampler        No Transaction
 control sampling PM10, PM2.5, Pb-                                                                           concentration and      reported as raw
 TSP, Pb-PM10.                                                                                duplicate sampler      data.
                                                                                concentration. \3\
Flow rate verification PM10 (low     Check of sampler flow   Each sampler..........  Once every month.....  Audit flow rate and    Flow Rate
 Vol) PM2.5, Pb-PM10.                 rate.                                                                  measured flow rate     Verification.
                                                                                indicated by the
                                                                                sampler.
Flow rate verification PM10 (High-   Check of sampler flow   Each sampler..........  Once every quarter...  Audit flow rate and    Flow Rate
 Vol), Pb-TSP.                        rate.                                                                  measured flow rate     Verification.
                                                                                indicated by the
                                                                                sampler.
Semi-annual flow rate audit PM10,    Check of sampler flow   Each sampler,.........  Once every 6 months..  Audit flow rate and    Semi Annual Flow Rate
 TSP, PM10-2.5, PM2.5, Pb-TSP, Pb-    rate using                                                             measured flow rate     Audit.
 PM10.                                independent standard.                                                  indicated by the
                                                                                sampler.
Pb analysis audits Pb-TSP, Pb-PM10.  Check of analytical     Analytical............  Once each quarter....  Measured value and     Pb Analysis Audits.
                                      system with Pb audit                                                   audit value (ug Pb/
                                      strips/filters.                                                        filter) using AQS
                                                                                unit code 077.
Performance Evaluation Program       Collocated samplers...  (1) 5 valid audits for  Distributed over all   Primary sampler        PEP.
 PM2.5.                                                       primary QA orgs, with   4 quarters.            concentration and
                                                              <= 5 sites..                                   performance
                                                             (2) 8 valid audits for                          evaluation sampler
                                                              primary QA orgs, with                          concentration.
                                                              >5 sites..
                                                             (3) All samplers in 6
                                                              years.
Performance Evaluation Program Pb-   Collocated samplers...  (1) 1 valid audit and   Distributed over all   Primary sampler        PEP.
 TSP, Pb-PM10.                                                4 collocated samples    4 quarters.            concentration and
                                                              for primary QA orgs,                           performance
                                                              with <=5 sites..                               evaluation sampler
                                                             (2) 2 valid audits and                          concentration.
                                                              6 collocated samples                           Primary sampler
                                                              for primary QA orgs                            concentration and
                                                              with >5 sites.                                 duplicate sampler
                                                                                concentration.
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Effective concentration for open path analyzers.
\2\ Corrected concentration, if applicable for open path analyzers.
\3\ Both primary and collocated sampler values are reported as raw data.
\4\ PM2.5 is the only particulate criteria pollutant requiring collocation of continuous and manual primary monitors.

      Table A-2 of Appendix A to Part 58--Summary of PM2.5 Number and Type of Collocation (15% Collocation
    Requirement) Required Using an Example of a PQAO That Has 54 Primary Monitors (54 sites) With One Federal
                  Reference Method Type and Three Types of Approved Federal Equivalent Methods
----------------------------------------------------------------------------------------------------------------
                                                                                No. of
                                                                                collocated
                                                   Total No. of    Total No. of       No. of         with same
       Primary sampler method designation            monitors       collocated      collocated        method
                                                                                with FRM       designation
                                                                                as primary
----------------------------------------------------------------------------------------------------------------
FRM.............................................              20               3               3               3
FEM (A).........................................              20               3               2               1
FEM (B).........................................               2               1               1               0
FEM (C).........................................              12               2               1               1
----------------------------------------------------------------------------------------------------------------

0
10. Add Appendix B to part 58 to read as follows:

Appendix B to Part 58--Quality Assurance Requirements for Prevention of
Significant Deterioration (PSD) Air Monitoring

1. General Information
2. Quality System Requirements
3. Measurement Quality Check Requirements
4. Calculations for Data Quality Assessments
5. Reporting Requirements
6. References

1. General Information

    1.1 Applicability.
    (a) This appendix specifies the minimum quality assurance
requirements for the control and assessment of the quality of the
ambient air monitoring data submitted to a PSD reviewing authority
or the EPA by an organization operating an air monitoring station,
or network of stations, operated in order to comply with Part 51 New
Source Review--Prevention of Significant Deterioration (PSD). Such
organizations are encouraged to develop and maintain quality
assurance programs more extensive than the required minimum.
Additional guidance for the requirements reflected in this appendix
can be found in the ``Quality Assurance Handbook for Air Pollution
Measurement Systems,'' Volume II (Ambient Air) and ``Quality
Assurance Handbook for Air Pollution Measurement Systems,'' Volume
IV (Meteorological Measurements) and at a national level in
references 1, 2, and 3 of this appendix.
    (b) It is not assumed that data generated for PSD under this
appendix will be used in making NAAQS decisions. However, if all the
requirements in this appendix are followed (including the NPEP
programs) and reported to AQS, with review and concurrence from the
EPA region, data may be used for NAAQS decisions. With the exception
of the NPEP programs (NPAP, PM2.5 PEP, Pb-PEP), for which
implementation is at the discretion of the PSD reviewing authority,
all other quality assurance and quality control requirements found
in the appendix must be met.
    1.2 PSD Primary Quality Assurance Organization (PQAO). A PSD
PQAO is defined as a monitoring organization or a coordinated
aggregation of such organizations that is responsible for a set of
stations within one PSD reviewing authority that monitors the same
pollutant and for which data quality assessments will be pooled.
Each criteria pollutant sampler/monitor must be associated with only
one PSD PQAO.
    1.2.1 Each PSD PQAO shall be defined such that measurement
uncertainty among all stations in the organization can be expected
to be reasonably homogeneous, as a result of common factors. A PSD
PQAO must be associated with only one PSD reviewing authority.
Common factors that should be considered in defining PSD PQAOs
include:
    (a) Operation by a common team of field operators according to a
common set of procedures;
    (b) Use of a common QAPP and/or standard operating procedures;
    (c) Common calibration facilities and standards;
    (d) Oversight by a common quality assurance organization; and
    (e) Support by a common management organization or laboratory.
    1.2.2 PSD monitoring organizations having difficulty describing
its PQAO or in assigning specific monitors to a PSD PQAO should
consult with the PSD reviewing authority. Any consolidation of PSD
PQAOs shall be subject to final approval by the PSD reviewing
authority.
    1.2.3 Each PSD PQAO is required to implement a quality system
that provides sufficient information to assess the quality of the
monitoring data. The quality system must, at a minimum, include the
specific requirements described in this appendix. Failure to conduct
or pass a required check or procedure, or a series of required
checks or procedures, does not by itself invalidate data for
regulatory decision making. Rather, PSD PQAOs and the PSD reviewing
authority shall use the checks and procedures required in this
appendix in combination with other data quality information,
reports, and similar documentation that demonstrate overall
compliance with parts 51, 52 and 58 of this chapter. Accordingly,
the PSD reviewing authority shall use a ``weight of evidence''
approach when determining the suitability of data for regulatory
decisions. The PSD reviewing authority reserves the authority to use
or not use monitoring data submitted by a PSD monitoring
organization when making regulatory decisions based on the PSD
reviewing authority's assessment of the quality of the data.
Generally, consensus built validation templates or validation
criteria already approved in quality assurance project plans (QAPPs)
should be used as the basis for the weight of evidence approach.
    1.3 Definitions.
    (a) Measurement Uncertainty. A term used to describe deviations
from a true concentration or estimate that are related to the
measurement process and not to spatial or temporal population
attributes of the air being measured.
    (b) Precision. A measurement of mutual agreement among
individual measurements of the same property usually under
prescribed similar conditions, expressed generally in terms of the
standard deviation.
    (c) Bias. The systematic or persistent distortion of a
measurement process which causes errors in one direction.
    (d) Accuracy. The degree of agreement between an observed value
and an accepted reference value. Accuracy includes a combination of
random error (imprecision) and systematic error (bias) components
which are due to sampling and analytical operations.
    (e) Completeness. A measure of the amount of valid data obtained
from a measurement system compared to the amount that was expected
to be obtained under correct, normal conditions.
    (f) Detectability. The low critical range value of a
characteristic that a method specific procedure can reliably
discern.
    1.4 Measurement Quality Check Reporting. The measurement quality
checks described in section 3 of this appendix, are required to be
submitted to the PSD reviewing authority within the same time frame
as routinely-collected ambient concentration data as described in 40
CFR 58.16. The PSD reviewing authority may as well require that the
measurement quality check data be reported to AQS.
    1.5 Assessments and Reports. Periodic assessments and
documentation of data quality are required to be reported to the PSD
reviewing authority. To provide national uniformity in this
assessment and reporting of data quality for all networks, specific
assessment and reporting procedures are prescribed in detail in
sections 3, 4, and 5 of this appendix.

2. Quality System Requirements

    A quality system (reference 1 of this appendix) is the means by
which an organization manages the quality of the monitoring
information it produces in a

systematic, organized manner. It provides a framework for planning,
implementing, assessing and reporting work performed by an
organization and for carrying out required quality assurance and
quality control activities.
    2.1 Quality Assurance Project Plans. All PSD PQAOs must develop
a quality system that is described and approved in quality assurance
project plans (QAPP) to ensure that the monitoring results:
    (a) Meet a well-defined need, use, or purpose (reference 5 of
this appendix);
    (b) Provide data of adequate quality for the intended monitoring
objectives;
    (c) Satisfy stakeholder expectations;
    (d) Comply with applicable standards specifications;
    (e) Comply with statutory (and other legal) requirements; and
    (f) Assure quality assurance and quality control adequacy and
independence.
    2.1.1 The QAPP is a formal document that describes these
activities in sufficient detail and is supported by standard
operating procedures. The QAPP must describe how the organization
intends to control measurement uncertainty to an appropriate level
in order to achieve the objectives for which the data are collected.
The QAPP must be documented in accordance with EPA requirements
(reference 3 of this appendix).
    2.1.2 The PSD PQAO's quality system must have adequate resources
both in personnel and funding to plan, implement, assess and report
on the achievement of the requirements of this appendix and it's
approved QAPP.
    2.1.3 Incorporation of quality management plan (QMP) elements
into the QAPP. The QMP describes the quality system in terms of the
organizational structure, functional responsibilities of management
and staff, lines of authority, and required interfaces for those
planning, implementing, assessing and reporting activities involving
environmental data operations (EDO). The PSD PQAOs may combine
pertinent elements of the QMP into the QAPP rather than requiring
the submission of both QMP and QAPP documents separately, with prior
approval of the PSD reviewing authority. Additional guidance on QMPs
can be found in reference 2 of this appendix.
    2.2 Independence of Quality Assurance Management. The PSD PQAO
must provide for a quality assurance management function for its PSD
data collection operation, that aspect of the overall management
system of the organization that determines and implements the
quality policy defined in a PSD PQAO's QAPP. Quality management
includes strategic planning, allocation of resources and other
systematic planning activities (e.g., planning, implementation,
assessing and reporting) pertaining to the quality system. The
quality assurance management function must have sufficient technical
expertise and management authority to conduct independent oversight
and assure the implementation of the organization's quality system
relative to the ambient air quality monitoring program and should be
organizationally independent of environmental data generation
activities.
    2.3 Data Quality Performance Requirements.
    2.3.1 Data Quality Objectives (DQOs). The DQOs, or the results
of other systematic planning processes, are statements that define
the appropriate type of data to collect and specify the tolerable
levels of potential decision errors that will be used as a basis for
establishing the quality and quantity of data needed to support air
monitoring objectives (reference 5 of the appendix). The DQOs have
been developed by the EPA to support attainment decisions for
comparison to national ambient air quality standards (NAAQS). The
PSD reviewing authority and the PSD monitoring organization will be
jointly responsible for determining whether adherence to the EPA
developed NAAQS DQOs specified in appendix A of this part are
appropriate or if DQOs from a project-specific systematic planning
process are necessary.
    <IP_ADDRESS> Measurement Uncertainty for Automated and Manual PM2.5
Methods. The goal for acceptable measurement uncertainty for
precision is defined as an upper 90 percent confidence limit for the
coefficient of variation (CV) of 10 percent and plus or minus 10
percent for total bias.
    <IP_ADDRESS> Measurement Uncertainty for Automated Ozone Methods. The
goal for acceptable measurement uncertainty is defined for precision
as an upper 90 percent confidence limit for the CV of 7 percent and
for bias as an upper 95 percent confidence limit for the absolute
bias of 7 percent.
    <IP_ADDRESS> Measurement Uncertainty for Pb Methods. The goal for
acceptable measurement uncertainty is defined for precision as an
upper 90 percent confidence limit for the CV of 20 percent and for
bias as an upper 95 percent confidence limit for the absolute bias
of 15 percent.
    <IP_ADDRESS> Measurement Uncertainty for NO2. The goal for acceptable
measurement uncertainty is defined for precision as an upper 90
percent confidence limit for the CV of 15 percent and for bias as an
upper 95 percent confidence limit for the absolute bias of 15
percent.
    <IP_ADDRESS> Measurement Uncertainty for SO2. The goal for acceptable
measurement uncertainty for precision is defined as an upper 90
percent confidence limit for the CV of 10 percent and for bias as an
upper 95 percent confidence limit for the absolute bias of 10
percent.
    2.4 National Performance Evaluation Program. Organizations
operating PSD monitoring networks are required to implement the
EPA's national performance evaluation program (NPEP) if the data
will be used for NAAQS decisions and at the discretion of the PSD
reviewing authority if PSD data are not used for NAAQS decisions.
The NPEP includes the National Performance Audit Program (NPAP), the
PM2.5 Performance Evaluation Program (PM2.5-
PEP) and the Pb Performance Evaluation Program (Pb-PEP). The PSD
QAPP shall provide for the implementation of NPEP including the
provision of adequate resources for such NPEP if the data will be
used for NAAQS decisions or if required by the PSD reviewing
authority. Contact the PSD reviewing authority to determine the best
procedure for implementing the audits which may include an audit by
the PSD reviewing authority, a contractor certified for the
activity, or through self-implementation which is described in
sections below. A determination of which entity will be performing
this audit program should be made as early as possible and during
the QAPP development process. The PSD PQAOs, including contractors
that plan to implement these programs on behalf of PSD PQAOs, that
plan to implement these programs (self-implement) rather than use
the federal programs, must meet the adequacy requirements found in
the appropriate sections that follow, as well as meet the definition
of independent assessment that follows.
    2.4.1 Independent Assessment. An assessment performed by a
qualified individual, group, or organization that is not part of the
organization directly performing and accountable for the work being
assessed. This auditing organization must not be involved with the
generation of the routinely-collected ambient air monitoring data.
An organization can conduct the performance evaluation (PE) if it
can meet this definition and has a management structure that, at a
minimum, will allow for the separation of its routine sampling
personnel from its auditing personnel by two levels of management.
In addition, the sample analysis of audit filters must be performed
by a laboratory facility and laboratory equipment separate from the
facilities used for routine sample analysis. Field and laboratory
personnel will be required to meet the performance evaluation field
and laboratory training and certification requirements. The PSD PQAO
will be required to participate in the centralized field and
laboratory standards certification and comparison processes to
establish comparability to federally implemented programs.
    2.5 Technical Systems Audit Program. The PSD reviewing authority
or the EPA may conduct system audits of the ambient air monitoring
programs or organizations operating PSD networks. The PSD monitoring
organizations shall consult with the PSD reviewing authority to
verify the schedule of any such technical systems audit. Systems
audit programs are described in reference 10 of this appendix.
    2.6 Gaseous and Flow Rate Audit Standards.
    2.6.1 Gaseous pollutant concentration standards (permeation
devices or cylinders of compressed gas) used to obtain test
concentrations for carbon monoxide (CO), sulfur dioxide
(SO2), nitrogen oxide (NO), and nitrogen dioxide
(NO2) must be traceable to either a National Institute of
Standards and Technology (NIST) Traceable Reference Material (NTRM)
or a NIST-certified Gas Manufacturer's Internal Standard (GMIS),
certified in accordance with one of the procedures given in
reference 4 of this appendix. Vendors advertising certification with
the procedures provided in reference 4 of this appendix and
distributing gases as ``EPA Protocol Gas'' must participate in the
EPA Protocol Gas Verification Program or not use ``EPA'' in any form
of advertising. The PSD PQAOs must provide information to the PSD
reviewing authority on the gas vendors they use (or will use) for
the duration of the PSD monitoring project. This information can

be provided in the QAPP or monitoring plan, but must be updated if
there is a change in the producer used.
    2.6.2 Test concentrations for ozone (O3) must be
obtained in accordance with the ultraviolet photometric calibration
procedure specified in appendix D to Part 50, and by means of a
certified NIST-traceable O3 transfer standard. Consult
references 7 and 8 of this appendix for guidance on transfer
standards for O3.
    2.6.3 Flow rate measurements must be made by a flow measuring
instrument that is NIST-traceable to an authoritative volume or
other applicable standard. Guidance for certifying some types of
flow-meters is provided in reference 10 of this appendix.
    2.7 Primary Requirements and Guidance. Requirements and guidance
documents for developing the quality system are contained in
references 1 through 11 of this appendix, which also contain many
suggested procedures, checks, and control specifications. Reference
10 describes specific guidance for the development of a quality
system for data collected for comparison to the NAAQS. Many specific
quality control checks and specifications for methods are included
in the respective reference methods described in Part 50 or in the
respective equivalent method descriptions available from the EPA
(reference 6 of this appendix). Similarly, quality control
procedures related to specifically designated reference and
equivalent method monitors are contained in the respective operation
or instruction manuals associated with those monitors. For PSD
monitoring, the use of reference and equivalent method monitors are
required.

3. Measurement Quality Check Requirements

    This section provides the requirements for PSD PQAOs to perform
the measurement quality checks that can be used to assess data
quality. Data from these checks are required to be submitted to the
PSD reviewing authority within the same time frame as routinely-
collected ambient concentration data as described in 40 CFR 58.16.
Table B-1 of this appendix provides a summary of the types and
frequency of the measurement quality checks that are described in
this section. Reporting these results to AQS may be required by the
PSD reviewing authority.
    3.1 Gaseous monitors of SO2, NO2, O3, and CO.
    3.1.1 One-Point Quality Control (QC) Check for SO2, NO2, O3, and
CO. (a) A one-point QC check must be performed at least once every 2
weeks on each automated monitor used to measure SO2,
NO2, O3 and CO. With the advent of automated
calibration systems, more frequent checking is strongly encouraged
and may be required by the PSD reviewing authority. See Reference 10
of this appendix for guidance on the review procedure. The QC check
is made by challenging the monitor with a QC check gas of known
concentration (effective concentration for open path monitors)
between the prescribed range of 0.005 and 0.08 parts per million
(ppm) for SO2, NO2, and O3, and
between the prescribed range of 0.5 and 5 ppm for CO monitors. The
QC check gas concentration selected within the prescribed range
should be related to monitoring objectives for the monitor. If
monitoring for trace level monitoring, the QC check concentration
should be selected to represent the mean or median concentrations at
the site. If the mean or median concentrations at trace gas sites
are below the MDL of the instrument the agency can select the lowest
concentration in the prescribed range that can be practically
achieved. If the mean or median concentrations at trace gas sites
are above the prescribed range the agency can select the highest
concentration in the prescribed range. The PSD monitoring
organization will consult with the PSD reviewing authority on the
most appropriate one-point QC concentration based on the objectives
of the monitoring activity. An additional QC check point is
encouraged for those organizations that may have occasional high
values or would like to confirm the monitors' linearity at the
higher end of the operational range or around NAAQS concentrations.
If monitoring for NAAQS decisions the QC concentration can be
selected at a higher concentration within the prescribed range but
should also consider precision points around mean or median
concentrations.
    (b) Point analyzers must operate in their normal sampling mode
during the QC 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. The QC check must be conducted before any
calibration or adjustment to the monitor.
    (c) Open-path monitors are tested by inserting a test cell
containing a QC 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 QC check gas in the test cell must be selected to produce an
effective concentration in the range specified earlier in this
section. Generally, the QC test concentration measurement will be
the sum of the atmospheric pollutant concentration and the QC test
concentration. As such, 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 QC test from the QC
check gas 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 monitors should be tested
during periods when the atmospheric pollutant concentrations are
relatively low and steady.
    (d) Report the audit concentration of the QC gas and the
corresponding measured concentration indicated by the monitor. The
percent differences between these concentrations are used to assess
the precision and bias of the monitoring data as described in
sections 4.1.2 (precision) and 4.1.3 (bias) of this appendix.
    3.1.2 Quarterly performance evaluation for SO2, NO2, O3, or CO.
Evaluate each primary monitor each monitoring quarter (or 90 day
frequency) during which monitors are operated or a least once (if
operated for less than one quarter). The quarterly performance
evaluation (quarterly PE) must be performed by a qualified
individual, group, or organization that is not part of the
organization directly performing and accountable for the work being
assessed. The person or entity performing the quarterly PE must not
be involved with the generation of the routinely-collected ambient
air monitoring data. A PSD monitoring organization can conduct the
quarterly PE itself if it can meet this definition and has a
management structure that, at a minimum, will allow for the
separation of its routine sampling personnel from its auditing
personnel by two levels of management. The quarterly PE also
requires a set of equipment and standards independent from those
used for routine calibrations or zero, span or precision checks.
    <IP_ADDRESS> The evaluation is made by challenging the monitor with
audit gas standards of known concentration from at least three audit
levels. One point must be within two to three times the method
detection limit of the instruments within the PQAOs network, the
second point will be less than or equal to the 99th percentile of
the data at the site or the network of sites in the PQAO or the next
highest audit concentration level. The third point can be around the
primary NAAQS or the highest 3-year concentration at the site or the
network of sites in the PQAO. An additional 4th level is encouraged
for those PSD organizations that would like to confirm the monitor's
linearity at the higher end of the operational range. In rare
circumstances, there may be sites measuring concentrations above
audit level 10. These sites should be identified to the PSD
reviewing authority.

----------------------------------------------------------------------------------------------------------------
                                                                     Concentration range, ppm
                   Audit level                   ---------------------------------------------------------------
                                                        O3              SO2             NO2             CO
----------------------------------------------------------------------------------------------------------------
1...............................................    0.004-0.0059   0.0003-0.0029   0.0003-0.0029     0.020-0.059
2...............................................     0.006-0.019   0.0030-0.0049   0.0030-0.0049     0.060-0.199

3...............................................     0.020-0.039   0.0050-0.0079   0.0050-0.0079     0.200-0.899
4...............................................     0.040-0.069   0.0080-0.0199   0.0080-0.0199     0.900-2.999
5...............................................     0.070-0.089   0.0200-0.0499   0.0200-0.0499     3.000-7.999
6...............................................     0.090-0.119   0.0500-0.0999   0.0500-0.0999    8.000-15.999
7...............................................     0.120-0.139   0.1000-0.1499   0.1000-0.2999   16.000-30.999
8...............................................     0.140-0.169   0.1500-0.2599   0.3000-0.4999   31.000-39.999
9...............................................     0.170-0.189   0.2600-0.7999   0.5000-0.7999   40.000-49.999
10..............................................     0.190-0.259    0.8000-1.000    0.8000-1.000   50.000-60.000
----------------------------------------------------------------------------------------------------------------

    <IP_ADDRESS> The NO2 audit techniques may vary depending
on the ambient monitoring method. For chemiluminescence-type
NO2 analyzers, gas phase titration (GPT) techniques
should be based on the EPA guidance documents and monitoring agency
experience. The NO2 gas standards may be more appropriate
than GPT for direct NO2 methods that do not employ
converters. Care should be taken to ensure the stability of such gas
standards prior to use.
    <IP_ADDRESS> The standards from which audit gas test concentrations
are obtained must meet the specifications of section 2.6.1 of this
appendix.
    <IP_ADDRESS> For point analyzers, the evaluation shall be carried out
by allowing the monitor to analyze the audit gas test atmosphere in
its normal sampling mode such that the test atmosphere passes
through all filters, scrubbers, conditioners, and other sample inlet
components used during normal ambient sampling and as much of the
ambient air inlet system as is practicable.
    <IP_ADDRESS> Open-path monitors are evaluated by inserting a test
cell containing the various audit gas concentrations 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 evaluation, and the normal
monitoring configuration of the instrument should be modified as
little as possible to accommodate the test cell for the evaluation.
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
evaluation level ranges specified in this section of this appendix.
Generally, each evaluation concentration measurement result will be
the sum of the atmospheric pollutant concentration and the
evaluation test concentration. As such, 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 evaluation
test (or preferably before and after each evaluation concentration
level) from the evaluation concentration measurement. If the
difference between the before and after measurements is greater than
20 percent of the effective concentration of the test gas standard,
discard the test result for that concentration level and repeat the
test for that level. If possible, open-path monitors should be
evaluated during periods when the atmospheric pollutant
concentrations are relatively low and steady. Also, if the open-path
instrument is not installed in a permanent manner, the monitoring
path length must be reverified to be within 3 percent to
validate the evaluation, since the monitoring path length is
critical to the determination of the effective concentration.
    <IP_ADDRESS> Report both the evaluation concentrations (effective
concentrations for open-path monitors) of the audit gases and the
corresponding measured concentration (corrected concentrations, if
applicable, for open-path monitors) indicated or produced by the
monitor being tested. The percent differences between these
concentrations are used to assess the quality of the monitoring data
as described in section 4.1.1 of this appendix.
    3.1.3 National Performance Audit Program (NPAP). As stated in
sections 1.1 and 2.4, PSD monitoring networks may be subject to the
NPEP, which includes the NPAP. The NPAP is a performance evaluation
which is a type of audit where quantitative data are collected
independently in order to evaluate the proficiency of an analyst,
monitoring instrument and laboratory. Due to the implementation
approach used in this program, NPAP provides for a national
independent assessment of performance with a consistent level of
data quality. The NPAP should not be confused with the quarterly PE
program described in section 3.1.2. The PSD organizations shall
consult with the PSD reviewing authority or the EPA regarding
whether the implementation of NPAP is required and the
implementation options available. Details of the EPA NPAP can be
found in reference 11 of this appendix. The program requirements
include:
    <IP_ADDRESS> Performing audits on 100 percent of monitors and sites
each year including monitors and sites that may be operated for less
than 1 year. The PSD reviewing authority has the authority to
require more frequent audits at sites they consider to be high
priority.
    <IP_ADDRESS> Developing a delivery system that will allow for the
audit concentration gasses to be introduced at the probe inlet where
logistically feasible.
    <IP_ADDRESS> Using audit gases that are verified against the National
Institute for Standards and Technology (NIST) standard reference
methods or special review procedures and validated annually for CO,
SO2 and NO2, and at the beginning of each
quarter of audits for O3.
    <IP_ADDRESS> The PSD PQAO may elect to self-implement NPAP. In these
cases, the PSD reviewing authority will work with those PSD PQAOs to
establish training and other technical requirements to establish
comparability to federally implemented programs. In addition to
meeting the requirements in sections <IP_ADDRESS> through <IP_ADDRESS>, the
PSD PQAO must:
    (a) Ensure that the PSD audit system is equivalent to the EPA
NPAP audit system and is an entirely separate set of equipment and
standards from the equipment used for quarterly performance
evaluations. If this system does not generate and analyze the audit
concentrations, as the EPA NPAP system does, its equivalence to the
EPA NPAP system must be proven to be as accurate under a full range
of appropriate and varying conditions as described in section
<IP_ADDRESS>.
    (b) Perform a whole system check by having the PSD audit system
tested at an independent and qualified EPA lab, or equivalent.
    (c) Evaluate the system with the EPA NPAP program through
collocated auditing at an acceptable number of sites each year (at
least one for a PSD network of five or less sites; at least two for
a network with more than five sites).
    (d) Incorporate the NPAP into the PSD PQAO's QAPP.
    (e) Be subject to review by independent, EPA-trained personnel.
    (f) Participate in initial and update training/certification
sessions.
    3.2 PM2.5.
    3.2.1 Flow Rate Verification for PM2.5. A one-point flow rate
verification check must be performed at least once every month (each
verification minimally separated by 14 days) on each monitor used to
measure PM2.5. The verification is made by checking the
operational flow rate of the monitor. If the verification is made in
conjunction with a flow rate adjustment, it must be made prior to
such flow rate adjustment. For the standard procedure, use a flow
rate transfer standard certified in accordance with section 2.6 of
this appendix to check the monitor's normal flow rate. Care should
be used in selecting and using the flow rate measurement device such
that it does not alter the normal operating flow rate of the
monitor. Flow rate verification results are to be reported to the
PSD reviewing authority quarterly as described in section 5.1.
Reporting these results to AQS is encouraged. The percent
differences between the audit

and measured flow rates are used to assess the bias of the
monitoring data as described in section 4.2.2 of this appendix
(using flow rates in lieu of concentrations).
    3.2.2 Semi-Annual Flow Rate Audit for PM2.5. Every 6 months,
audit the flow rate of the PM2.5 particulate monitors.
For short-term monitoring operations (those less than 1 year), the
flow rate audits must occur at start up, at the midpoint, and near
the completion of the monitoring project. The audit must be
conducted by a trained technician other than the routine site
operator. The audit is made by measuring the monitor's normal
operating flow rate using a flow rate transfer standard certified in
accordance with section 2.6 of this appendix. The flow rate standard
used for auditing must not be the same flow rate standard used for
verifications or to calibrate the monitor. However, both the
calibration standard and the audit standard may be referenced to the
same primary flow rate or volume standard. Care must be taken in
auditing the flow rate to be certain that the flow measurement
device does not alter the normal operating flow rate of the monitor.
Report the audit flow rate of the transfer standard and the
corresponding flow rate measured by the monitor. The percent
differences between these flow rates are used to evaluate monitor
performance.
    3.2.3 Collocated Sampling Procedures for PM2.5. A PSD PQAO must
have at least one collocated monitor for each PSD monitoring
network.
    <IP_ADDRESS> For each pair of collocated monitors, designate one
sampler as the primary monitor whose concentrations will be used to
report air quality for the site, and designate the other as the QC
monitor. There can be only one primary monitor at a monitoring site
for a given time period.
    (a) If the primary monitor is a FRM, then the quality control
monitor must be a FRM of the same method designation.
    (b) If the primary monitor is a FEM, then the quality control
monitor must be a FRM unless the PSD PQAO submits a waiver for this
requirement, provides a specific reason why a FRM cannot be
implemented, and the waiver is approved by the PSD reviewing
authority. If the waiver is approved, then the quality control
monitor must be the same method designation as the primary FEM
monitor.
    <IP_ADDRESS> In addition, the collocated monitors should be deployed
according to the following protocol:
    (a) The collocated quality control monitor(s) should be deployed
at sites with the highest predicted daily PM2.5
concentrations in the network. If the highest PM2.5
concentration site is impractical for collocation purposes,
alternative sites approved by the PSD reviewing authority may be
selected. If additional collocated sites are necessary, the PSD PQAO
and the PSD reviewing authority should determine the appropriate
location(s) based on data needs.
    (b) The two collocated monitors must be within 4 meters of each
other and at least 2 meters apart for flow rates greater than 200
liters/min or at least 1 meter apart for samplers having flow rates
less than 200 liters/min to preclude airflow interference. A waiver
allowing up to 10 meters horizontal distance and up to 3 meters
vertical distance (inlet to inlet) between a primary and collocated
quality control monitor may be approved by the PSD reviewing
authority for sites at a neighborhood or larger scale of
representation. This waiver may be approved during the QAPP review
and approval process. Sampling and analytical methodologies must be
the consistently implemented for both collocated samplers and for
all other samplers in the network.
    (c) Sample the collocated quality control monitor on a 6-day
schedule for sites not requiring daily monitoring and on a 3-day
schedule for any site requiring daily monitoring. Report the
measurements from both primary and collocated quality control
monitors at each collocated sampling site. The calculations for
evaluating precision between the two collocated monitors are
described in section 4.2.1 of this appendix.
    3.2.4 PM2.5 Performance Evaluation Program (PEP) Procedures. As
stated in sections 1.1 and 2.4 of this appendix, PSD monitoring
networks may be subject to the NPEP, which includes the
PM2.5 PEP. The PSD monitoring organizations shall consult
with the PSD reviewing authority or the EPA regarding whether the
implementation of PM2.5 PEP is required and the
implementation options available for the PM2.5 PEP. For
PSD PQAOs with less than or equal to five monitoring sites, five
valid performance evaluation audits must be collected and reported
each year. For PSD PQAOs with greater than five monitoring sites,
eight valid performance evaluation audits must be collected and
reported each year. Additionally, within the five or eight required
audits, each type of method designation (FRM/FEM designation) used
as a primary monitor in the PSD network shall be audited. For a PE
to be valid, both the primary monitor and PEP audit measurements
must meet quality control requirements and be above 3 [mu]g/m\3\ or
a predefined lower concentration level determined by a systematic
planning process and approved by the PSD reviewing authority. Due to
the relatively short-term nature of most PSD monitoring, the
likelihood of measuring low concentrations in many areas attaining
the PM2.5 standard and the time required to weigh filters
collected in PEs, a PSD monitoring organization's QAPP may contain a
provision to waive the 3 [micro]g/m\3\ threshold for validity of PEs
conducted in the last quarter of monitoring, subject to approval by
the PSD reviewing authority.
    3.3 PM10.
    3.3.1 Flow Rate Verification for PM10. A one-point flow rate
verification check must be performed at least once every month (each
verification minimally separated by 14 days) on each monitor used to
measure PM10. The verification is made by checking the
operational flow rate of the monitor. If the verification is made in
conjunction with a flow rate adjustment, it must be made prior to
such flow rate adjustment. For the standard procedure, use a flow
rate transfer standard certified in accordance with section 2.6 of
this appendix to check the monitor's normal flow rate. Care should
be taken in selecting and using the flow rate measurement device
such that it does not alter the normal operating flow rate of the
monitor. The percent differences between the audit and measured flow
rates are used to assess the bias of the monitoring data as
described in section 4.2.2 of this appendix (using flow rates in
lieu of concentrations).
    3.3.2 Semi-Annual Flow Rate Audit for PM10. Every 6 months,
audit the flow rate of the PM10 particulate monitors. For
short-term monitoring operations (those less than 1 year), the flow
rate audits must occur at start up, at the midpoint, and near the
completion of the monitoring project. Where possible, the EPA
strongly encourages more frequent auditing. The audit must be
conducted by a trained technician other than the routine site
operator. The audit is made by measuring the monitor's normal
operating flow rate using a flow rate transfer standard certified in
accordance with section 2.6 of this appendix. The flow rate standard
used for auditing must not be the same flow rate standard used for
verifications or to calibrate the monitor. However, both the
calibration standard and the audit standard may be referenced to the
same primary flow rate or volume standard. Care must be taken in
auditing the flow rate to be certain that the flow measurement
device does not alter the normal operating flow rate of the monitor.
Report the audit flow rate of the transfer standard and the
corresponding flow rate measured by the monitor. The percent
differences between these flow rates are used to evaluate monitor
performance
    3.3.3 Collocated Sampling Procedures for Manual PM10. A PSD PQAO
must have at least one collocated monitor for each PSD monitoring
network.
    <IP_ADDRESS> For each pair of collocated monitors, designate one
sampler as the primary monitor whose concentrations will be used to
report air quality for the site, and designate the other as the
quality control monitor.
    <IP_ADDRESS> In addition, the collocated monitors should be deployed
according to the following protocol:
    (a) The collocated quality control monitor(s) should be deployed
at sites with the highest predicted daily PM10
concentrations in the network. If the highest PM10
concentration site is impractical for collocation purposes,
alternative sites approved by the PSD reviewing authority may be
selected.
    (b) The two collocated monitors must be within 4 meters of each
other and at least 2 meters apart for flow rates greater than 200
liters/min or at least 1 meter apart for samplers having flow rates
less than 200 liters/min to preclude airflow interference. A waiver
allowing up to 10 meters horizontal distance and up to 3 meters
vertical distance (inlet to inlet) between a primary and collocated
sampler may be approved by the PSD reviewing authority for sites at
a neighborhood or larger scale of representation. This waiver may be
approved during the QAPP review and approval process. Sampling and
analytical methodologies must be the consistently implemented for
both collocated samplers and for all other samplers in the network.

    (c) Sample the collocated quality control monitor on a 6-day
schedule or 3-day schedule for any site requiring daily monitoring.
Report the measurements from both primary and collocated quality
control monitors at each collocated sampling site. The calculations
for evaluating precision between the two collocated monitors are
described in section 4.2.1 of this appendix.
    (d) In determining the number of collocated sites required for
PM10, PSD monitoring networks for Pb-PM10
should be treated independently from networks for particulate matter
(PM), even though the separate networks may share one or more common
samplers. However, a single quality control monitor that meets the
collocation requirements for Pb-PM10 and PM10
may serve as a collocated quality control monitor for both networks.
Extreme care must be taken if using the filter from a quality
control monitor for both PM10 and Pb analysis.
PM10 filter weighing should occur prior to any Pb
analysis.
    3.4 Pb.
    3.4.1 Flow Rate Verification for Pb. A one-point flow rate
verification check must be performed at least once every month (each
verification minimally separated by 14 days) on each monitor used to
measure Pb. The verification is made by checking the operational
flow rate of the monitor. If the verification is made in conjunction
with a flow rate adjustment, it must be made prior to such flow rate
adjustment. Use a flow rate transfer standard certified in
accordance with section 2.6 of this appendix to check the monitor's
normal flow rate. Care should be taken in selecting and using the
flow rate measurement device such that it does not alter the normal
operating flow rate of the monitor. The percent differences between
the audit and measured flow rates are used to assess the bias of the
monitoring data as described in section 4.2.2 of this appendix
(using flow rates in lieu of concentrations).
    3.4.2 Semi-Annual Flow Rate Audit for Pb. Every 6 months, audit
the flow rate of the Pb particulate monitors. For short-term
monitoring operations (those less than 1 year), the flow rate audits
must occur at start up, at the midpoint, and near the completion of
the monitoring project. Where possible, the EPA strongly encourages
more frequent auditing. The audit must be conducted by a trained
technician other than the routine site operator. The audit is made
by measuring the monitor's normal operating flow rate using a flow
rate transfer standard certified in accordance with section 2.6 of
this appendix. The flow rate standard used for auditing must not be
the same flow rate standard used to in verifications or to calibrate
the monitor. However, both the calibration standard and the audit
standard may be referenced to the same primary flow rate or volume
standard. Great care must be taken in auditing the flow rate to be
certain that the flow measurement device does not alter the normal
operating flow rate of the monitor. Report the audit flow rate of
the transfer standard and the corresponding flow rate measured by
the monitor. The percent differences between these flow rates are
used to evaluate monitor performance.
    3.4.3 Collocated Sampling for Pb. A PSD PQAO must have at least
one collocated monitor for each PSD monitoring network.
    <IP_ADDRESS> For each pair of collocated monitors, designate one
sampler as the primary monitor whose concentrations will be used to
report air quality for the site, and designate the other as the
quality control monitor.
    <IP_ADDRESS> In addition, the collocated monitors should be deployed
according to the following protocol:
    (a) The collocated quality control monitor(s) should be deployed
at sites with the highest predicted daily Pb concentrations in the
network. If the highest Pb concentration site is impractical for
collocation purposes, alternative sites approved by the PSD
reviewing authority may be selected.
    (b) The two collocated monitors must be within 4 meters of each
other and at least 2 meters apart for flow rates greater than 200
liters/min or at least 1 meter apart for samplers having flow rates
less than 200 liters/min to preclude airflow interference. A waiver
allowing up to 10 meters horizontal distance and up to 3 meters
vertical distance (inlet to inlet) between a primary and collocated
sampler may be approved by the PSD reviewing authority for sites at
a neighborhood or larger scale of representation. This waiver may be
approved during the QAPP review and approval process. Sampling and
analytical methodologies must be the consistently implemented for
both collocated samplers and all other samplers in the network.
    (c) Sample the collocated quality control monitor on a 6-day
schedule if daily monitoring is not required or 3-day schedule for
any site requiring daily monitoring. Report the measurements from
both primary and collocated quality control monitors at each
collocated sampling site. The calculations for evaluating precision
between the two collocated monitors are described in section 4.2.1
of this appendix.
    (d) In determining the number of collocated sites required for
Pb-PM10, PSD monitoring networks for PM10
should be treated independently from networks for Pb-
PM10, even though the separate networks may share one or
more common samplers. However, a single quality control monitor that
meets the collocation requirements for Pb-PM10 and
PM10 may serve as a collocated quality control monitor
for both networks. Extreme care must be taken if using a using the
filter from a quality control monitor for both PM10 and
Pb analysis. The PM10 filter weighing should occur prior
to any Pb analysis.
    3.4.4 Pb Analysis Audits. Each calendar quarter, audit the Pb
reference or equivalent method analytical procedure using filters
containing a known quantity of Pb. These audit filters are prepared
by depositing a Pb standard on unexposed filters and allowing them
to dry thoroughly. The audit samples must be prepared using batches
of reagents different from those used to calibrate the Pb analytical
equipment being audited. Prepare audit samples in the following
concentration ranges:

------------------------------------------------------------------------
                                              Equivalent ambient Pb
                 Range                     concentration, [micro]g/m\3\
------------------------------------------------------------------------
1......................................  30-100% of Pb NAAQS.
2......................................  200-300% of Pb NAAQS.
------------------------------------------------------------------------

    (a) Audit samples must be extracted using the same extraction
procedure used for exposed filters.
    (b) Analyze three audit samples in each of the two ranges each
quarter samples are analyzed. The audit sample analyses shall be
distributed as much as possible over the entire calendar quarter.
    (c) Report the audit concentrations (in [micro]g Pb/filter or
strip) and the corresponding measured concentrations (in [micro]g
Pb/filter or strip) using AQS unit code 077 (if reporting to AQS).
The percent differences between the concentrations are used to
calculate analytical accuracy as described in section 4.2.5 of this
appendix.
    3.4.5 Pb Performance Evaluation Program (PEP) Procedures. As
stated in sections 1.1 and 2.4, PSD monitoring networks may be
subject to the NPEP, which includes the Pb PEP. The PSD monitoring
organizations shall consult with the PSD reviewing authority or the
EPA regarding whether the implementation of Pb-PEP is required and
the implementation options available for the Pb-PEP. The PEP is an
independent assessment used to estimate total measurement system
bias. Each year, one PE audit must be performed at one Pb site in
each PSD PQAO network that has less than or equal to five sites and
two audits for PSD PQAO networks with greater than five sites. In
addition, each year, four collocated samples from PSD PQAO networks
with less than or equal to five sites and six collocated samples
from PSD PQAO networks with greater than five sites must be sent to
an independent laboratory for analysis. The calculations for
evaluating bias between the primary monitor and the PE monitor for
Pb are described in section 4.2.4 of this appendix.

4. Calculations for Data Quality Assessments

    (a) Calculations of measurement uncertainty are carried out by
PSD PQAO according to the following procedures. The PSD PQAOs should
report the data for all appropriate measurement quality checks as
specified in this appendix even though they may elect to perform
some or all of the calculations in this section on their own.
    (b) At low concentrations, agreement between the measurements of
collocated samplers, expressed as relative percent difference or
percent difference, may be relatively poor. For this reason,
collocated measurement pairs will be selected for use in the
precision and bias calculations only when both measurements are
equal to or above the following limits:
    (1) Pb: 0.002 [micro]g/m\3\ (Methods approved after 3/04/2010,
with exception of manual equivalent method EQLA-0813-803).
    (2) Pb: 0.02 [micro]g/m\3\ (Methods approved before 3/04/2010,
and manual equivalent method EQLA-0813-803).
    (3) PM10 (Hi-Vol): 15 [micro]g/m\3\.
    (4) PM10 (Lo-Vol): 3 [micro]g/m\3\.
    (5) PM2.5: 3 [micro]g/m\3\.

    (c) The PM2.5 3 [micro]g/m\3\ limit for the
PM2.5-PEP may be superseded by mutual agreement between
the PSD PQAO and the PSD reviewing authority as specified in section
3.2.4 of the appendix and detailed in the approved QAPP.
    4.1 Statistics for the Assessment of QC Checks for SO2, NO2, O3
and CO.
    4.1.1 Percent Difference. Many of the measurement quality checks
start with a comparison of an audit concentration or value (flow-
rate) to the concentration/value measured by the monitor and use
percent difference as the comparison statistic as described in
equation 1 of this section. For each single point check, calculate
the percent difference, di, as follows:
[GRAPHIC] [TIFF OMITTED] TR28MR16.008

where meas is the concentration indicated by the PQAO's instrument
and audit is the audit concentration of the standard used in the QC
check being measured.