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PROCEDURE 6. QUALITY ASSURANCE REQUIREMENTS FOR GASEOUS
HYDROGEN CHLORIDE (HCL) CONTINUOUS EMISSION MONITORING
SYSTEMS USED FOR COMPLIANCE DETERMINATION AT STATIONARY
SOURCES
1.0 Applicability and Principle
1.1 Applicability. Procedure 6 is used to evaluate the effectiveness of quality control (QC) and
quality assurance (QA) procedures and evaluate the quality of data produced by any hydrogen
chloride (HC1) gas, CAS: 7647-01-0, continuous emission monitoring system (CEMS) that is
used for determining compliance with emission standards for HC1 on a continuous basis as
specified in an applicable permit or regulation.
1.1.1 This procedure specifies the minimum QA requirements necessary for the control and
assessment of the quality of CEMS data submitted to the Environmental Protection Agency
(EPA) or a delegated authority. If you are responsible for one or more CEMS used for HC1
compliance monitoring you must meet these minimum requirements and you are encouraged to
develop and implement a more extensive QA program or to continue such programs where they
already exist.
1.1.2 Data collected as a result of QA and QC measures required in this procedure are to be
submitted to the EPA or the delegated authority in accordance with the applicable regulation or
permit. These data are to be used by both the delegated authority and you, as the CEMS operator,
in assessing the effectiveness of the CEMS QC and QA procedures in the maintenance of
acceptable CEMS operation and valid emission data.
1.2 Principle
1.2.1 The QA procedures consist of two distinct and equally important functions. One function
is the assessment of the quality of the CEMS data by estimating accuracy. The other function is
the control and improvement of the quality of the CEMS data by implementing QC policies and
corrective actions. These two functions form an iterative control loop. When the assessment
function indicates that the data quality is inadequate, the control effort must be increased until
the data quality is acceptable. In order to provide uniformity in the assessment and reporting of
data quality, this procedure specifies the assessment procedures to evaluate response drift and
accuracy. The procedures specified are based on Performance Specification 18 (PS-18) in
appendix B to this part.
(Note: Because the control and corrective action function encompasses a variety of policies,
specifications, standards and corrective measures, this procedure treats QC requirements in
general terms to allow you, as source owner or operator to develop the most effective and
efficient QC system for your circumstances.)
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2.0 Definitions
See PS-18 of this subpart for the primary definitions used in this Procedure.
3.0 QC Requirements
3.1 You, as a source owner or operator, must develop and implement a QC program. At a
minimum, each QC program must include written procedures and/or manufacturer's information
which should describe in detail, complete, step-by-step procedures and operations for each of the
following activities:
(a) Calibration Drift (CD) checks of CEMS;
(b) CD determination and adjustment of CEMS;
(c) Integrated Path (IP) CEMS temperature and pressure sensor accuracy checks;
(d) IP CEMS beam intensity checks;
(e) Routine and preventative maintenance of CEMS (including spare parts inventory);
(f) Data recording, calculations, and reporting;
(g) Accuracy audit procedures for CEMS including reference method(s); and
(h) Program of corrective action for malfunctioning CEMS.
3.2 These written procedures must be kept on site and available for inspection by the delegated
authority. As described in section 5.4, whenever excessive inaccuracies occur for two
consecutive quarters, you must revise the current written procedures, or modify or replace the
CEMS to correct the deficiency causing the excessive inaccuracies.
4.0 Daily Data Quality Requirements and Measurement Standardization Procedures
4.1 CD Assessment. An upscale gas, used to meet a requirement in this section must be either a
NIST-traceable reference gas or a gas certified by the gas vendor to ±5.0 percent accuracy.
4.1.1 CD Requirement. Consistent with 40 CFR 60.13(d) and 63.8(c), you, as source owners or
operators of CEMS must check, record, and quantify the CD at two levels, using a zero gas and
mid-level gas at least once daily (approximately every 24 hours). Perform the CD check in
accordance with the procedure in applicable performance specification (e.g., section 11.8 of PS-
18 in appendix B of this part). The daily zero- and mid-level CD must not exceed two times the
drift limits specified in the applicable performance specification (e.g., section 13.2 of PS-18 in
appendix B to this part.)
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4.1.2 Recording Requirement for CD Corrective action. Corrective actions taken to bring a
CEMS back in control after exceeding a CD limit must be recorded and reported with the
associated CEMS data. Reporting corrective action must include the unadjusted concentration
measured prior to resetting the calibration and the adjusted value after resetting the calibration to
bring the CEMS back into control.
4.1.3 Dynamic Spiking Option for Mid-level CD. For extractive CEMS, you have the option to
conduct a daily dynamic spiking procedure found in section 11.8.8 of PS-18 of appendix B of
this part in lieu of the daily mid-level CD check. If this option is selected, the daily zero CD
check is still required.
4.1.4 Out of Control Criteria for Excessive CD. As specified in §63.8(c)(7)(i)(A), a CEMS is
out of control if the zero or mid-level CD exceeds two times the applicable CD specification in
the applicable PS or in the relevant standard. When a CEMS is out of control, you as owner or
operator of the affected source must take the necessary corrective actions and repeat the tests that
caused the system to go out of control (in this case, the failed CD check) until the applicable
performance requirements are met.
4.1.5 Additional Quality Assurance for Data above Span. This procedure must be used when
required by an applicable regulation and may be used when significant data above span are being
collected. Furthermore, the terms of this procedure do not apply to the extent that alternate terms
are otherwise specified in an applicable rule or permit.
4.1.5.1 Any time the average measured concentration of HC1 exceeds 150 percent of the span
value for two consecutive one-hour averages, conduct the following 'above span' CEMS response
check.
4.1.5.1.1 Within a period of 24 hours (before or after) of the 'above span' period, introduce a
higher, 'above span' HC1 reference gas standard to the CEMS. Use 'above span' reference gas that
meets the requirements of section 7.0 of PS-18 and target a concentration level between 75 and
125 percent of the highest hourly concentration measured during the period of measurements
above span.
4.1.5.1.2 Introduce the reference gas at the probe for extractive CEMS or for IP-CEMS as an
equivalent path length corrected concentration in the instrument calibration cell.
4.1.5.1.3 At no time may the 'above span' concentration exceed the analyzer full-scale range.
4.1.5.2 Record and report the results of this procedure as you would for a daily calibration. The
'above span' response check is successful if the value measured by the CEMS is within 20
percent of the certified value of the reference gas.
4.1.5.3 If the 'above span' response check is conducted during the period when measured
emissions are above span and there is a failure to collect at least one data point in an hour due to
the response check duration, then determine the emissions average for that missed hour as the
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average of hourly averages for the hour preceding the missed hour and the hour following the
missed hour.
4.1.5.4 In the event that the 'above span' response check is not successful {i.e., the CEMS
measured value is not within 20 percent of the certified value of the reference gas), then you
must normalize the one-hour average stack gas values measured above the span during the 24-
hour period preceding or following the 'above span' response check for reporting based on the
CEMS response to the reference gas as shown in Eq. 6-1:
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4.2 Beam Intensity Requirement for HCl IP-CEMS.
4.2.1 Beam Intensity Measurement. If you use a HCl IP-CEMS, you must quantify and record
the beam intensity of the IP-CEMS in appropriate units at least once daily (approximately 24
hours apart) according to manufacturer's specifications and procedures.
4.2.2 Out of Control Criteria for Excessive Beam Intensity Loss. If the beam intensity falls
below the level established for the operation range determined following the procedures in
section 11.2 of PS-18 of this part, then your CEMS is out-of-control. This quality check is
independent of whether the CEMS daily CD is acceptable. If your CEMS is out-of-control, take
necessary corrective action. You have the option to repeat the beam intensity test procedures in
section 11.2 of PS-18 to expand the acceptable range of acceptable beam intensity. Following
corrective action, repeat the beam intensity check.
4.3 Out Of Control Period Duration for Daily Assessments. The beginning of the out-of-control
period is the hour in which the owner or operator conducts a daily performance check
{e.g., calibration drift or beam intensity check) that indicates an exceedance of the performance
requirements established under this procedure. The end of the out-of-control period is the
completion of daily assessment of the same type following corrective actions, which shows that
the applicable performance requirements have been met.
4.4 CEMS Data Status During Out-of-Control Period. During the period the CEMS is out-of-
control, the CEMS data may not be used in calculating compliance with an emissions limit nor
be counted towards meeting minimum data availability as required and described in the
applicable regulation or permit.
5.0 Data Accuracy Assessment
You must audit your CEMS for the accuracy of HCl measurement on a regular basis at the
frequency described in this section, unless otherwise specified in an applicable regulation or
permit. Quarterly audits are performed at least once each calendar quarter. Successive quarterly
audits, to the extent practicable, shall occur no closer than 2 months apart. Annual audits are
performed at least once every four consecutive calendar quarters.
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5.1 Temperature and Pressure Accuracy Assessment for IP CEMS.
5.1.1 Stack or source gas temperature measurement audits for HC1IP-CEMS must be
conducted and recorded at least annually in accordance with the procedure described in section
11.3 of PS-18 in appendix B to this part. As an alternative, temperature measurement devices
may be replaced with certified instruments on an annual basis. Units removed from service may
be bench tested against an NIST traceable sensor and reused during subsequent years. Any
measurement instrument or device that is used to conduct ongoing verification of temperature
measurement must have an accuracy that is traceable to NIST.
5.1.2 Stack or source gas pressure measurement audits for HC1 IP-CEMS must be conducted
and recorded at least annually in accordance with the procedure described in section 11.4 of PS-
18 in appendix B of this part. As an alternative, pressure measurement devices may be replaced
with certified instruments on an annual basis. Units removed from service may be bench tested
against an NIST traceable sensor and reused during subsequent years. Any measurement
instrument or device that is used to conduct ongoing verification of pressure measurement must
have an accuracy that is traceable to NIST.
5.1.3 Out of Control Criteria for Excessive Parameter Verification Inaccuracy. If the
temperature or pressure verification audit exceeds the criteria in sections 5.3.4.5 and 5.3.4.6,
respectively, the CEMS is out-of-control. If the CEMS is out-of-control, take necessary
corrective action to eliminate the problem. Following corrective action, you must repeat the
failed verification audit until the temperature or pressure measurement device is operating within
the applicable specifications, at which point the out-of-control period ends.
5.2 Concentration Accuracy Auditing Requirements. Unless otherwise specified in an
applicable rule or permit, you must audit the HC1 measurement accuracy of each CEMS at least
once each calendar quarter, except in the case where the affected facility is off-line (does not
operate). In that case, the audit must be performed as soon as is practicable in the quarter in
which the unit recommences operation. Successive quarterly audits must, to the extent
practicable, be performed no less than 2 months apart. The accuracy audits shall be conducted as
follows:
5.2.1 Relative Accuracy Test Audit. A RATA must be conducted at least once every four
calendar quarters, except as otherwise noted in sections 5.2.5 or 5.5 of this procedure. Perform
the RATA as described in section 11.9 of PS-18 in appendix B to this part. If the HC1
concentration measured by the RM during a RATA (in ppmv) is less than or equal to 20 percent
of the concentration equivalent to the applicable emission standard, you must perform a Cylinder
Gas Audit (CGA) or a Dynamic Spike Audit (DSA) for at least one subsequent (one of the
following three) quarterly accuracy audits.
5.2.2 Quarterly Relative Accuracy Audit (RAA). A quarterly RAA may be conducted as an
option to conducting a RATA in three of four calendar quarters, but in no more than three
quarters in succession. To conduct an RAA, follow the test procedures in section 11.9 of PS-18
in appendix B to this part, except that only three test runs are required. The difference between
the mean of the RM values and the mean of the CEMS responses relative to the mean of the RM
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values (or alternatively the emission standard) is used to assess the accuracy of the CEMS.
Calculate the RAA results as described in section 6.2. As an alternative to an RAA, a cylinder
gas audit or a dynamic spiking audit may be conducted.
5.2.3 Cylinder Gas Audit. A quarterly CGA may be conducted as an option to conducting a
RATA in three of four calendar quarters, but in no more than three consecutive quarters. To
perform a CGA, challenge the CEMS with a zero-level and two upscale level audit gases of
known concentrations within the following ranges:
Audit point
Audit range
1 (Mid-Level)
50 to 60% of span value.
2 (High-Level)
80 to 100% of span value.
5.2.3.1 Inject each of the three audit gases (zero and two upscale) three times each for a total of
nine injections. Inject the gases in such a manner that the entire CEMS is challenged. Do not
inject the same gas concentration twice in succession.
5.2.3.2 Use HC1 audit gases that meet the requirements of section 7 of PS-18 in appendix B to
this part.
5.2.3.3 Calculate results as described in section 6.3.
5.2.4 Dynamic Spiking Audit. For extractive CEMS, a quarterly DSA may be conducted as an
option to conducting a RATA in three of four calendar quarters, but in no more than three
quarters in succession.
5.2.4.1 To conduct a DSA, you must challenge the entire HC1 CEMS with a zero gas in
accordance with the procedure in section 11.8 of PS-18 in appendix B of this part. You must also
conduct the DS procedure as described in appendix A to PS-18 of appendix B to this part. You
must conduct three spike injections with each of two upscale level audit gases. The upscale level
gases must meet the requirements of section 7 of PS-18 in appendix B to this part and must be
chosen to yield concentrations at the analyzer of 50 to 60 percent of span and 80 to 100 percent
of span. Do not inject the same gas concentration twice in succession.
5.2.4.2 Calculate results as described in section 6.4. To determine CEMS accuracy, you must
calculate the dynamic spiking error (DSE) for each of the two upscale audit gases using Equation
A5 in appendix A to PS-18 and Equation 6-3 in section 6.4 of Procedure 6 in appendix B to this
part.
5.2.5 Other Alternative Quarterly Audits. Other alternative audit procedures, as approved by the
Administrator, may be used for three of four calendar quarters.
5.3 Out of Control Criteria for Excessive Audit Inaccuracy. If the results of the RATA, RAA,
CGA, or DSA do not meet the applicable performance criteria in section 5.3.4, the CEMS is out-
of-control. If the CEMS is out-of-control, take necessary corrective action to eliminate the
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problem. Following corrective action, the CEMS must pass a test of the same type that resulted
in the out-of-control period to determine if the CEMS is operating within the specifications
(e.g., a RATA must always follow an out-of-control period resulting from a RATA).
5.3.1 If the audit results show the CEMS to be out-of-control, you must report both the results
of the audit showing the CEMS to be out-of-control and the results of the audit following
corrective action showing the CEMS to be operating within specifications.
5.3.2 Out-Of-Control Period Duration for Excessive Audit Inaccuracy. The beginning of the
out-of-control period is the time corresponding to the completion of the sampling for the failed
RATA, RAA, CGA or DSA. The end of the out-of-control period is the time corresponding to
the completion of the sampling of the subsequent successful audit.
5.3.3 CEMS Data Status During Out-Of-Control Period. During the period the CEMS is out-of-
control, the CEMS data may not be used in calculating emission compliance nor be counted
towards meeting minimum data availability as required and described in the applicable
regulation or permit.
5.3.4 Criteria for Excessive Quarterly and Yearly Audit Inaccuracy. Unless specified otherwise
in the applicable regulation or permit, the criteria for excessive inaccuracy are:
5.3.4.1 For the RATA, the CEMS must meet the RA specifications in section 13.4 of PS-18 in
appendix B to this part.
5.3.4.2 For the CGA, the accuracy must not exceed 5.0 percent of the span value at the zero gas
and the mid- and high-level reference gas concentrations.
5.3.4.3 For the RAA, the RA must not exceed 20.0 percent of the RMavg as calculated using
Equation 6-2 in section 6.2 of this procedure whether calculated in units of HC1 concentration or
in units of the emission standard. In cases where the RA is calculated on a concentration (ppmv)
basis, if the average HC1 concentration measured by the RM during the test is less than 75
percent of the HC1 concentration equivalent to the applicable standard, you may substitute the
equivalent emission standard value (in ppmvw) in the denominator of Equation 6-2 in the place
of RMavg and the result of this alternative calculation of RA must not exceed 15.0 percent.
5.3.4.4 For DSA, the accuracy must not exceed 5.0 percent of the span value at the zero gas and
the mid- and high-level reference gas concentrations or 20.0 percent of the applicable emission
standard, whichever is greater.
5.3.4.5 For the gas temperature measurement audit, the CEMS must satisfy the requirements in
section 13.7 in PS-18 of appendix B to this part.
5.3.4.6 For the gas pressure measurement audit, the CEMS must satisfy the requirements in
section 13.8 in PS-18 of appendix B to this part.
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5.4 Criteria for Acceptable QC Procedures. Repeated excessive inaccuracies {i.e., out-of-control
conditions resulting from the quarterly or yearly audits) indicate that the QC procedures are
inadequate or that the CEMS is incapable of providing quality data. Therefore, whenever
excessive inaccuracies occur for two consecutive quarters, you must revise the QC procedures
(see section 3.0) or modify or replace the CEMS.
5.5 Criteria for Optional QA Test Frequency. If all the quality criteria are met in sections 4 and
5 of this procedure, the CEMS is in-control.
5.5.1 Unless otherwise specified in an applicable rule or permit, if the CEMS is in-control and
if your source emits <75 percent of the HC1 emission limit for each averaging period as specified
in the relevant standard for eight consecutive quarters that include a minimum of two RAT As,
you may revise your auditing procedures to use CGA, RAA or DSA each quarter for seven
subsequent quarters following a RATA.
5.5.2 You must perform at least one RATA that meets the acceptance criteria every 2 years.
5.5.3 If you fail a RATA, RAA, CGA, or DSA, then the audit schedule in section 5.2 must be
followed until the audit results meet the criteria in section 5.3.4 to start requalifying for the
optional QA test frequency in section 5.5.
6.0 Calculations for CEMS Data Accuracy
6.1 RATA RA Calculation. Follow Equations 9 through 14 in section 12 of PS-18 in appendix
B to this part to calculate the RA for the RATA. The RATA must be calculated either in units of
the applicable emission standard or in concentration units (ppmv).
6.2 RAA Accuracy Calculation. Use Equation 6-2 to calculate the accuracy for the RAA.
The RA may be calculated in concentration units (ppmv) or in the units of the applicable
emission standard.
HA -—. UK! Hj K|
Where:
RA = Accuracy of the CEMS (percent)
MNavg = Average measured CEMS response during the audit in units of applicable standard or
appropriate concentration.
RMavg = Average reference method value in units of applicable standard or appropriate
concentration.
6.3 CGA Accuracy Calculation. For each gas concentration, determine the average of the three
CEMS responses and subtract the average response from the audit gas value. For extractive
CEMS, calculate the ME at each gas level using Equation 3A in section 12.3 of PS-18 in
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appendix B to this part. For IP-CEMS, calculate the ME at each gas level using Equation 6A in
section 12.4.3 of PS-18 in appendix B to this part.
6.4 DSA Accuracy Calculation. DSA accuracy is calculated as a percent of span. To calculate
the DSA accuracy for each upscale spike concentration, first calculate the DSE using Equation
A5 in appendix A of PS-18 in appendix B to this part. Then use Equation 6-3 to calculate the
average DSA accuracy for each upscale spike concentration. To calculate DSA accuracy at the
zero level, use equation 3A in section 12.3 of PS-18 in appendix B to this part.
7.0 Reporting Requirements
At the reporting interval specified in the applicable regulation or permit, report for each
CEMS the quarterly and annual accuracy audit results from section 6 and the daily assessment
results from section 4. Unless otherwise specified in the applicable regulation or permit, include
all data sheets, calculations, CEMS data records (i.e., charts, records of CEMS responses),
reference gas certifications and reference method results necessary to confirm that the
performance of the CEMS met the performance specifications.
7.1 Unless otherwise specified in the applicable regulations or permit, report the daily
assessments (CD and beam intensity) and accuracy audit information at the interval for
emissions reporting required under the applicable regulations or permits.
7.1.1 At a minimum, the daily assessments and accuracy audit information reporting must
contain the following information:
a. Company name and address.
b. Identification and location of monitors in the CEMS.
c. Manufacturer and model number of each monitor in the CEMS.
d. Assessment of CEMS data accuracy and date of assessment as determined by a RATA,
RAA, CGA or DSA described in section 5 including:
i. The RA for the RATA;
ii. The accuracy for the CGA, RAA, or DSA;
iiii. Temperature and pressure sensor audit results for IP-CEMS;
iv. The RM results, the reference gas certified values;
DSA Aa:unuy » :::i :: : - !Oil
v. The CEMS responses;
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vi. The calculation results as defined in section 6; and
vii. Results from the performance audit samples described in section 5 and the applicable
RMs.
e. Summary of all out-of-control periods including corrective actions taken when CEMS
was determined out-of-control, as described in sections 4 and 5.
7.1.2 If the accuracy audit results show the CEMS to be out-of-control, you must report both
the audit results showing the CEMS to be out-of-control and the results of the audit following
corrective action showing the CEMS to be operating within specifications.
8.0 Bibliography
1. EPA Traceability Protocol for Assay and Certification of Gaseous Calibration Standards, U.S.
Environmental Protection Agency office of Research and Development, EPA/600/R-12/531,
May 2012.
2. Method 205, "Verification of Gas Dilution Systems for Field Instrument Calibrations," 40
CFR part 51, appendix M.
9.0 Tables, Diagrams, Flowcharts [Reserved]
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