The EPA Administrator, Gina McCarthy, signed the following notice on 6/25/2015, and EPA is submitting it for

publication in the Federal Register (FR). While we have taken steps to ensure the accuracy of this Internet version

of the rule, it is not the official version of the rule for purposes of compliance. Please refer to the official version in

a forthcoming FR publication, which will appear on the Government Printing Office's FDSys website

(http://gpo.gov/fdsys/search/home.action) and on Regulations.gov (http://www.regulations.gov) in Docket No.

EPA‐HQ‐OAR‐2013‐0696. Once the official version of this document is published in the FR, this version will be

removed from the Internet and replaced with a link to the official version.

6560-50-P 

ENVIRONMENTAL PROTECTION AGENCY 

40 CFR Part 60 

[EPA-HQ-OAR-2013-0696; FRL-9929-25-OAR]

RIN 2060-AR81 

Performance Specification 18 – Performance Specifications and Test Procedures for 

Hydrogen Chloride Continuous Emission Monitoring Systems at Stationary Sources 

AGENCY: Environmental Protection Agency (EPA). 

ACTION: Final rule. 

SUMMARY: The Environmental Protection Agency (EPA) is finalizing performance 

specifications and test procedures for hydrogen chloride (HCl) continuous emission monitoring 

systems (CEMS) to provide sources and regulatory agencies with criteria and test procedures for 

evaluating the acceptability of HCl CEMS. The final performance specification (Performance 

Specification 18) includes requirements for initial acceptance, including instrument accuracy and 

stability assessments. This action also finalizes quality assurance (QA) procedures for HCl 

CEMS used for compliance determination at stationary sources. The QA procedures (Procedure 

6) specify the minimum QA requirements necessary for the control and assessment of the quality 

of CEMS data submitted to the EPA. 

This action establishes consistent requirements for ensuring and assessing the quality of 

HCl data measured by CEMS. The affected systems are those used for determining compliance 

with emission standards for HCl on a continuous basis as specified in an applicable permit or 

regulation. The affected industries and their North American Industry Classification System 
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(NAICS) codes are listed in the SUPPLEMENTARY INFORMATION section of this 

preamble.

DATES: This final rule is effective on [insert date of publication in the Federal Register]. 

ADDRESSES: Docket: The EPA has established a docket for this rulemaking under Docket ID 

No. EPA-HQ-OAR-2013-0696. All documents in the docket are listed on the 

www.regulations.gov website. Although listed in the index, some information is not publicly 

available, e.g., Confidential Business Information (CBI) or other information whose disclosure is 

restricted by statute. Certain other material, such as copyrighted material, is not placed on the 

Internet and will be publicly available only in hard copy form. Publicly available docket 

materials are available either electronically through www.regulations.gov or in hard copy at the 

EPA Docket Center, Room 3334, EPA WJC West Building, 1301 Constitution Ave., NW, 

Washington, DC 20004. The Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday 

through Friday, excluding legal holidays. The telephone number for the Public Reading Room is 

(202) 566-1744, and the telephone number for the EPA Docket Center is (202) 566-1742. 

FOR FURTHER INFORMATION CONTACT: Ms. Candace Sorrell, Office of Air Quality 

Planning and Standards, Air Quality Assessment Division (AQAD), Measurement Technology 

Group, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27709; 

telephone number: (919) 541-1064; fax number: (919) 541-0516; email address: 

sorrell.candace@epa.gov. 

SUPPLEMENTARY INFORMATION: 

 The information in this preamble is organized as follows: 

I. General Information 

A. Does this action apply to me? 

B. Where can I get a copy of this document and other related information? 

C. Judicial Review 
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II. Background 

III. Changes Included in the Final Performance Specification 18 and Procedure 6 

IV. Summary of Major Comments and Responses 

A. Dynamic Spiking 

B. Duplicate Trains When Performing RATA 

C. Stratification Test Requirements 

D. Calibration Range Above Span 

E. RATA Acceptance Criteria for Low Concentration Sources 

V. Statutory and Executive Order Reviews 

A. Executive Order 12866: Regulatory Planning and Review and Executive Order 13563: 

Improving Regulation and Regulatory Review 

B. Paperwork Reduction Act (PRA) 

C. Regulatory Flexibility Act (RFA) 

D. Unfunded Mandates Reform Act (UMRA) 

E. Executive Order 13132: Federalism 

F. Executive Order 13175: Consultation and Coordination with Indian Tribal Governments 

G. Executive Order 13045: Protection of Children From Environmental Health Risks and Safety 

Risks 

H. Executive Order 13211: Actions Concerning Regulations That Significantly Affect Energy 

Supply, Distribution, or Use 

I. National Technology Transfer and Advancement Act (NTTAA) 

J. Executive Order 12898: Federal Actions To Address Environmental Justice in Minority 

Populations and Low-Income Populations 

K. Congressional Review Act (CRA) 

I. General Information 

A. Does this action apply to me? 

The major entities that would potentially be affected by the final Performance 

Specification 18 (PS-18) and the QA requirements of Procedure 6 for gaseous HCl CEMS are 

those entities that are required to install a new HCl CEMS, relocate an existing HCl CEMS, or 

replace an existing HCl CEMS under any applicable subpart of 40 CFR parts 60, 61, or 63. Table 

1 of this preamble lists the current federal rules by subpart and the corresponding source 

categories to which the PS-18 and Procedure 6 potentially would apply. 

TABLE 1. SOURCE CATEGORIES THAT WOULD POTENTIALLY BE SUBJECT TO 

PS-18 AND PROCEDURE 6 
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Subpart(s) Source Category 

40 CFR part 63 

Subpart LLL Portland Cement Manufacturing Industry 

Subpart UUUUU Coal- and Oil-fired 

Electric Utility Steam Generating Units 

The requirements of PS-18 and Procedure 6 may also apply to stationary sources located 

in a state, district, reservation, or territory that adopts PS-18 or Procedure 6 in its implementation 

plan. 

We plan to amend 40 CFR part 63 subpart UUUUU, National Emission Standards for 

Hazardous Air Pollutants: Coal- and Oil-fired Electric Utility Steam Generating Units to offer 

PS-18 and Procedure 6 as an alternative to Performance Specification 15 (PS-15) for continuous 

monitoring of HCl. On February 17, 2015 (80 FR 8442), we proposed amendments to appendix 

B of subpart UUUUU that clarify that PS-18 and Procedure 6 will be allowed and how they are 

to be implemented under subpart UUUUU. Note, prior to the time that these amendments are 

finalized, the alternative test method approval process of 40 CFR 63.7(f) is available as a way for 

affected facilities to request approval to use PS-18/Procedure 6 in lieu of PS-15. 

With regard to 40 CFR part 63, Subpart LLL, which affects Portland cement 

manufacturing facilities and includes HCl monitoring requirements, no amendments will be 

needed as Subpart LLL already allows for use of any promulgated performance specification for 

HCl CEMS in 40 CFR part 60, appendix B. 

Table 2 lists the corresponding NAICS codes for the source categories listed in Table 1 of 

this preamble. 

TABLE 2. NAICS FOR POTENTIALLY REGULATED ENTITIES 

Industry NAICS Codes 

Fossil Fuel-Fired Electric Utility Steam Generating Units 221112a
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221122b

921150c 

Portland Cement Manufacturing Plants 327310

a Industry in Indian Country 

b

 Federal, state, local/tribal government owned c

 Industry in Indian Country 

Tables 1 and 2 are not intended to be exhaustive, but rather they provide a guide for 

readers regarding entities potentially affected by this action. If you have any questions regarding 

the potential applicability of PS-18 and test procedures (Procedure 6) to a particular entity, 

consult the person listed in the FOR FURTHER INFORMATION CONTACT section.

B. Where can I get a copy of this document and other related information? 

In addition to being available in the docket, an electronic copy of this action is available 

on the Internet through the EPA’s Technology Transfer Network (TTN) website, a forum for 

information and technology exchange in various areas of air quality management, measurement 

standards and implementation, etc. Following publication in the Federal Register, the EPA will 

post the Federal Register version of the promulgation and key technical documents on the TTN 

website: http://www.epa.gov/ttn/emc/promulgated.html. 

C. Judicial Review 

 Under section 307(b)(1) of the Clean Air Act (CAA), judicial review of this final rule is 

available only by filing a petition for review in the U.S. Court of Appeals for the District of 

Columbia Circuit by [insert date 60 days after publication in Federal Register]. Under section 

307(d)(7)(B) of the CAA, only an objection to this final rule that was raised with reasonable 

specificity during the period for public comment can be raised during judicial review. Moreover, 

under section 307(b)(2) of the CAA, the requirements established by this final rule may not be 

challenged separately in any civil or criminal proceedings brought by the EPA to enforce these 
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requirements. Section 307(d)(7)(B) also provides a mechanism for us to convene a proceeding 

for reconsideration, “[i]f the person raising an objection can demonstrate to the EPA that it was 

impracticable to raise such objection within [the period for public comment] or if the grounds for 

such objection arose after the period for public comment (but within the time specified for 

judicial review) and if such objection is of central relevance to the outcome of the rule.” Any 

person seeking to make such a demonstration to us should submit a Petition for Reconsideration 

to the Office of the Administrator, U.S. EPA, Room 3000, William Jefferson Clinton Building, 

1200 Pennsylvania Ave., NW, Washington, DC 20460, with a copy to both the person(s) listed in 

the preceding FOR FURTHER INFORMATION CONTACT section, and the Associate 

General Counsel for the Air and Radiation Law Office, Office of General Counsel (Mail Code 

2344A), U.S. EPA, 1200 Pennsylvania Ave., NW, Washington, DC 20460. 

II. Background 

The EPA recently promulgated the Portland Cement Maximum Achievable Control 

Technology (MACT) rule (75 FR 54970, September 9, 2010; 78 FR 10006, February 12, 2013) 

and the Mercury and Air Toxics Standards (MATS) rule (77 FR 9303, February 16, 2012; 78 FR 

24075, April 24, 2013). Both rules specify the use of extractive Fourier transform infrared 

spectroscopy (FTIR) and PS-15 when affected facilities opt or are required to continuously 

measure HCl emissions. To facilitate use of alternative technologies to FTIR and to aid in 

measuring the low levels of HCl specified in those rules, the EPA has developed and is 

promulgating these new specifications and quality control (QC) procedures (PS-18 and 

Procedure 6) for HCl CEMS as an alternative to the use of PS-15. 

 Multiple technologies are available for HCl emissions monitoring. The goals of PS-18 

and Procedure 6 are (1) to allow for the use of different HCl CEMS sampling and analytical 
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technologies as long as the required performance criteria set out in the performance specification 

(PS) are met; and (2) to establish consistent requirements for ensuring and assessing the quality 

of data measured by a HCl CEMS. 

Performance Specification 18 and Procedure 6 were proposed on May 14, 2014 (79 FR 

27690). The initial public comment period was extended (from 30 to 60 days; ending July 13, 

2014) in response to commenter requests. We reviewed and considered comments on the 

proposed PS-18 and Procedure 6 and have made several changes to the specifications and QA 

procedures finalized with this action to address concerns and improve the proposed performance 

specifications and procedures. 

Under section 553(d) of the Administrative Procedures Act (APA), 5 U.S.C. 553(d), the 

agency may make a rule immediately effective “for good cause found and published with the 

rule.” For the reasons discussed below, the EPA believes there is “good cause” to make this 

amendment effective upon publication in the Federal Register. This rule establishes a new 

measurement option, and not a new underlying requirement. The sooner the new option is 

available, more flexibility will be provided to regulated parties. 

III. Changes Included in the Final Performance Specification 18 and Procedure 6 

This rule finalizes PS-18 and Procedure 6, as proposed, except with five revisions in 

response to public comments. First, we expanded the options for using dynamic spiking (DS) 

with extractive systems and clarified the spiking procedures for integrated path systems through 

the use of “method of standard additions” in daily QC checks and as a replacement for the 

quarterly relative accuracy audit (RAA). Next, we eliminated the requirement for paired or 

duplicate trains when performing relative accuracy test audits (RATAs) using Method 26A. This 

change was based on data provided by stakeholders and the EPA’s Office of Research and 
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Development, which showed that this reference method (RM) generated data acceptable to allay 

concerns about the data quality at concentrations near the compliance limit. In response to 

commenters who claimed that stratification testing is overly burdensome and unwarranted, we 

revised PS-18 to offer three RM traverse point options that can be used without the need for 

stratification testing and added clarifying language concerning the stratification testing 

procedures. We removed calibration range above span requirements in both PS-18 and Procedure 

6 because we decided, after considering concerns raised by commenters, that above span 

compliance requirements are best handled on a rule-specific basis within individual subparts 

regulating differing industries/categories. The procedures for assuring the quality of the data 

when an applicable regulation requires measurements above span were not removed. Lastly, we 

added flexibility to both PS-18 and Procedure 6 in the relative accuracy criteria. 

IV. Summary of Major Comments and Responses 

 A comprehensive summary of the comments received on the proposed PS-18 and 

procedures (Procedure 6) and our responses to those comments can be found in the Summary of 

Public Comments and Responses document,1 which is available in the docket for this action (see 

Docket No. EPA-HQ-OAR-2013-0696). Some of the major comments received on the PS and 

QA procedures and our responses to those comments are summarized by subject in the following 

paragraphs. 

A. Dynamic Spiking 

                                                            

1 U.S. Environmental Protection Agency. Response to Comments on Proposed Rule: Performance Specification 18 – 

Specifications and Test Procedures for Gaseous HCl Continuous Emission Monitoring Systems at Stationary 

Sources. Office of Air Quality Planning and Standards (OAQPS), Air Quality Assessment Division (AQAD), 

Research Triangle Park, NC; May 2015. 
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Under the proposed PS-18, we required DS into the CEMS using a National Institute of 

Standards and Technology (NIST) traceable standard to demonstrate initial performance at 

sources with emission levels near the detection limit of the CEMS. 

1. Expanded Use of Dynamic Spiking as an Optional QC Check 

Several comments received on the proposal recommended that the EPA allow for 

optional use of DS procedures for all certification and QA procedures as alternatives to using 

external calibration standards. Commenters opined that a choice between performing DS or daily 

zero and upscale checks should be available to the manufacturer and CEMS user for all CEMS 

technologies, and that the regulation should not mandate the use of either technique to exclude 

particular technologies. 

After consideration of comments, we have revised the final PS and QA procedures to 

allow for optional use of DS procedures for the following: 

(1) The upscale (mid-level) portion of the 7-day calibration drift test, 

(2) The daily mid-level CD check, and 

(3) The quarterly data accuracy assessments. 

In addition, if the source meets the criteria of section 5.5 in Procedure 6, we are allowing 

for a dynamic spiking audit (DSA) as a replacement for the RATA once every 2 years. 

A DS procedure does not provide sufficient information to replace the 7-day or daily zero 

CD check, the initial measurement error (ME) test, or completely replace the relative accuracy 

(RA) comparison with a RM. The 7-day and daily zero CD checks using exclusively zero gas 

provide an absolute check of the instrument zero. Should hysteresis be a concern, humidified 

zero gas may be used. 
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After consideration, we decided that DS was not a suitable replacement for the 7-day or 

daily zero CD check. We added an additional procedure for use of a DS as an option for the 7-

day and daily mid-level CD checks to section 11.8 of PS-18 and section 4.1 of Procedure 6 in the 

final rule. The acceptance criteria for use of a DS as a mid-level CD check is the same as that for 

the classic CD check procedure, +5 percent of span for a single spike; an equation has been 

added to appendix A of PS-18 for calculating this value. It is important to note that under the 

final rule, the 7-day and daily upscale CD checks (whether done using the classic procedure and 

pure calibration gases or done using a DS procedure) are limited to the use of a mid-level gas. 

The reason for this limitation is to (1) ensure that the upscale calibration is closer to the 

measured values, (2) mitigate hysteresis effects, and (3) ensure that the CD values determined 

using either the classic procedure or a DS procedure are on a consistent basis. 

We have retained the requirement for use of pure calibration gases as the only option for 

the ME test. We retained this requirement because we want (at least) an initial direct assessment 

of the linearity of the system; we do not believe that the nominal costs associated with hysteresis 

or gas use are critical concerns for this requirement for a one time test. 

Use of a DSA as an option for quarterly data accuracy assessment was included in the 

proposal for Procedure 6; and section 5.2.3 of Procedure 6 has been revised to include clarifying 

information on spike levels, number of spikes, and audit calculations. 

The final rule requires yearly conduct of a RATA involving comparison against a RM 

unless the optional criteria are met to reduce this requirement to every other year. The RATA 

provides quantitative assessment of the CEMS as well as confirmation of the continued 

representativeness of the CEMS sampling location. The DS option confirms the quantitative 
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output of the CEMS comparison but lacks the traversing necessary to evaluate representativeness 

of the CEMS sampling point. 

2. Removal of the Dynamic Spiking Requirement for Low Emission Sources 

We received several comments on the proposed specifications requiring a DS verification 

test whenever the HCl measurements are less than or equal to 20 percent of the applicable 

standard (in section 11.9.4.3) arguing that the provisions are unnecessary. One commenter 

asserted that there is no purpose or precedent for requiring alternative or additional QA testing, 

in addition to a RATA, because a unit is operating well below the applicable standard or the RM 

quantification limit and that having such a requirement does not appreciably provide any more 

assurances that the HCl CEMS is operating properly than demonstrated by meeting the RA 

requirements. One commenter asserted that kilns with very low or no HCl emissions should not 

be required to conduct extra tests and that DS procedures equivalent to those used in PS-15 DS 

should be allowed as an alternative to the RA test and not in addition to the RA test to validate 

installed CEMS. 

Upon review of these comments, we have decided that requiring a DS, merely because 

emissions are low, may present a disincentive to maintaining low emissions without appreciably 

assuring better operation of HCl CEMS. Therefore, we have revised PS-18 to remove this 

requirement for low HCl emission sources. 

B. Duplicate Trains When Performing RATA 

The proposed PS-18 required (1) paired or duplicate trains when performing RATAs 

using Method 26A as the RM and (2) invalidation of data pairs not meeting specified relative 

difference criteria (sections 11.9.4.4 and 11.9.4.6). 
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Several commenters requested that the requirement for paired trains be removed when 

Method 26A is used as the RM when conducting a RATA. Commenters argued that dual trains 

will add unnecessary time, more expense, and will complicate the testing process. These 

commenters generally opined that the additional burdens associated with requiring dual trains 

will not increase accuracy and will make it more unlikely that facilities will choose to implement 

HCl CEMS. 

Commenters generally expressed that both Method 26 and 26A have been widely used 

for a number of years to develop data both to set standards and to show compliance, and that 

Method 26A is very durable, well-designed, and provides accurate/high quality data. One 

commenter acknowledged that variability is higher as measurements get closer to the detection 

limit; however, the commenter asserted that this is true for any analytical method, not just 

Method 26A. Another commenter noted that Method 26A has a known negative bias below 20 

ppmv (parts per million by volume); however, this bias would show up in both trains (if a dual 

train was used) and would not have any impact on determining accuracy. 

One commenter reported that PS-12A is the only known PS that requires the use of 

paired RM sampling trains (see PS-12A, section 8.4.2), and requires dual trains when using 

Method 29. The commenter further reported that paired trains are recommended but not required 

in PS-11 (see section 8.6(1)(i)). The commenter suggested that the EPA adopt an alternative 

standard in which the EPA would recommend the use of paired trains, but not require them, 

similar to the requirements of PS-11. 

One commenter stated that random uncontrolled events can occur that can affect the 

results of a RM test, and if such an event occurs during a RATA, the sample may not meet the 

relative difference (RD) performance criteria and would count as one of a maximum of three 
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exclusions/rejections allowed in the proposed PS-18. This commenter contended that if dual 

trains are employed, there is twice the probability of a random event occurring that could result 

in a rejection. One commenter stated that requiring dual trains could result in the discarding of 

otherwise valid RM runs. 

Commenters asserted that if the RM data is of poor quality or there is a large enough 

error in the reference point, either that data point will have to be discarded (if allowed) or the 

instrument will not pass the RATA. One commenter opined that facilities should have the choice 

to use single trains and risk failing the RATA due to suspect RM data. 

We acknowledge that requiring duplicate Method 26A trains during RATA tests adds 

some complexity and cost to initial and ongoing quality demonstration of CEMS performance. 

Our primary concern is the confidence in RM data at low concentrations. We also acknowledge 

that the PS-18 proposal only requires duplicate sampling for Method 26A and does not address 

duplicate Method 320/Method 321 as a requirement during RATA testing. Furthermore, from the 

data provided by stakeholders and by the EPA’s Office of Research and Development 

(evaluating the use of paired Method 26A trains), we are convinced that Method 26A performs 

as a prescriptive method to generate data acceptable to allay concerns about the quality of this 

RM at concentrations at the compliance limits of current MACT rules. We have revised PS-18 to 

remove the requirement for paired reference Method 26A sampling trains during RATA tests. 

C. Stratification Test Requirements 

Several commenters opined that stratification testing is overly burdensome and 

unwarranted. 

One commenter opined that the stratification test would be overly burdensome for 

sources using Method 26A because test results would not be readily available onsite, which 
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would force sources to use instrumental methods (e.g., Method 320) that yield real time HCl 

data. Another commenter stated that the requirements for a stratification test for HCl are 

unwarranted because extractive CEM or cross-stack tunable diode laser (TDL) instruments are 

only effective in measuring HCl in the vapor phase, and stratification only occurs with non-vapor 

droplets and higher-mass aerosols. The commenter asserted that gas phase measurements have 

always been associated with a homogeneous mixture of molecules across a stack or duct under 

turbulent flow conditions, which is always the case at plants with HCl emission streams. The 

commenter asserted that other reasons why a stratification test is not warranted include (1) the 

fact that other extractive HCl RMs, including Methods 320, 321, and ASTM D6348-12, do not 

require a stratification test, and (2) if stratification exists and is statistically significant, the error 

would be revealed by the RA test. 

One commenter asserted that there may be units that would be subject to PS-18 under 

subpart UUUUU and other rules (e.g., 40 CFR part 75) that have already performed stratification 

testing at their RM sampling location. The commenter suggested that to avoid unnecessary 

repetitive stratification testing, the EPA include an exemption from the stratification testing 

requirement for RM locations that have been previously evaluated. 

Another commenter stated that the proposed stratification test procedures and acceptance 

criteria specified in section 11.9.3 of the proposal (1) are unnecessary for most sources and do 

not need to be performed, (2) contain confusing references to the CEMS and RM sampling 

points, (3) provide inappropriate acceptance criteria, and (4) are not supported by any data. 

One commenter suggested that the stratification test sections be revised to (1) eliminate 

the test when the monitor and RA test locations are downstream of induced draft (ID) fan or 

other well mixed location, (2) eliminate the test for sources that have no measurable HCl during 
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mill on operation, (3) explicitly state stratification tests should not be done during transient 

conditions including mill off operation, (4) specify that only an oxygen (O2) traverse is necessary 

if the only potential source of stratification is air in-leakage, (5) specify a stratification test, when 

necessary, be done at the RA test location and not the CEMS location, if different, and (6) 

specify that level of detection (LOD) criteria for allowing the alternative sulfur dioxide (SO2), 

carbon dioxide (CO2), and carbon monoxide (CO) tests are based on the RM LOD and not the 

CEMS LOD. 

One commenter also suggested that, unless the EPA can demonstrate that HCl 

stratification is an actual issue, the EPA should revise PS-18 to incorporate the identical 

requirements in PS-2, section 8.13.2, that requires sampling three points on a line, and require 

stratification tests only where there is a reason to expect stratification actually exists. The 

commenter also asserted that there is no need to acquire and use a series of EPA Protocol SO2

calibration gases and comprehensive series of procedures intended for test runs. 

We disagree with the commenters that stratification testing is unnecessary and overly 

burdensome. Contrary to the assertions of some commenters that stratification testing is not 

necessary, gaseous pollutants can be stratified. While turbulent flow and other conditions may 

eliminate stratification under certain conditions, the EPA does not agree that those conditions can 

be easily defined nor that if stratification exists, it would always be revealed by the RA test. It is 

the EPA’s position that to ensure collection of representative RM samples, it is necessary to 

confirm the absence of stratification before allowing single point or 3-point sampling that does 

not include the centroid of the duct. 

However, we do recognize that there is a need to provide one or more options for RM 

sample point selection that do not require stratification testing and we also understand that the 
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proposed language of section 11.9.3 may have caused some confusion. Therefore, we have 

revised PS-18 to offer three RM traverse point options that can be used without the need for 

stratification testing. These options are a 3-point traverse (commonly known as the a “3-point 

long line”) that includes the centroid of the duct, a 6-point traverse as allowed under 40 CFR part 

75, or a 12-point traverse, as was requested by one commenter. Testers desiring to test at a single 

point or at three points within two meters of a single port (commonly known as a “3-point short 

line”) will need to conduct stratification testing to demonstrate the absence of stratification or 

only minimal stratification, respectively. 

Additionally, after consideration of comments received on stratification testing, we have 

also revised the final PS-18 to: 

(1) Clarify that the purpose of stratification testing is only for selection of RM 

sampling points; 

(2) Simplify the use of SO2 as a surrogate for stratification testing without restriction 

to offer a simpler option when using Method 26A as the RM; 

(3) Clarify (as commenters have recommended) that stratification testing must be 

conducted at the same location as the RM testing; and 

(4) Clarify that stratification testing should not be conducted during transient 

conditions. 

D. Calibration Range Above Span 

Commenters expressed concern over the proposed requirements related to calibration 

range above span or CRAS (defined as the upper limit of the measurement range based on a 

conservatively high estimate of the range of HCl measurements expected from the source 

category). Specifically, commenters expressed concern that the proposed CRAS requirements: 
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(1) Conflict with the definition of “span” in both 40 CFR part 60, subpart UUUUU 

(subpart UUUUU), appendix A, and in 40 CFR part 75 (section 72.2). 

(2) Conflict with the recently promulgated 40 CFR part 63, subpart LLL (subpart 

LLL) requirements. 

(3) Would likely create one hour of unnecessary CEMS data loss each time it is 

performed in view of the time required for the CEMS to achieve and stabilize at the high 

concentration level and subsequently recover to the normal operating level. 

(4) Require that the HCl CEMS be adjusted when the calibration drift exceeds 0.5 

ppm (parts per million) at the zero or at 15-20 ppm levels. Commenters stated that 

upscale or CRAS levels would impose arbitrary adjustments simply chasing noise and 

that it should be changed to a requirement to inspect the CEMS and determine the proper 

corrective action. 

Commenters stated that the span and range of a CEMS depend on the type of technology 

used and that the EPA references the mercury CEMS as the precedent for the above span 

requirement. Commenters asserted that this can be problematic because, whereas mercury 

CEMSs have a linear response, other technologies may not have a linear response. 

After considering concerns raised by commenters, we decided that above span calibration 

requirements are best handled on a rule-specific basis within individual subparts regulating 

differing industries/categories. Therefore, we revised PS-18 and Procedure 6 to remove 

calibration range above span requirements and made them an option in Procedure 6. Subpart 

LLL-specific above span calibration technical revisions have been made under that rulemaking 

(see 79 FR 68821; November 19, 2014). 

E. RATA Acceptance Criteria for Low Concentration Sources 
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The proposed PS-18 section 5.3.5 referenced an alternative criterion for RA that would 

apply in instances where the emission level for the test is less than 50 percent of the applicable 

standard. The proposed alternative criterion was for when the RM result is less than 50 percent 

of the emission standard and the emission standard is used in the denominator of the equation for 

calculating RA to be less than or equal to 15 percent. We received comments that asserted that 

this requirement is inconsistent with other alternative RA options used in other performance 

specifications. Some commenters supported the use of an absolute value; i.e., plus or minus 1 

ppm if the RM is less than 3 ppm, which they reported would be similar to the requirements for 

mercury CEMS under subpart UUUUU. 

We recognize that calibration standards and measurement technology exist to 

demonstrate the quality of HCl emission measurements at or above 1 ppm and that existing 

CEMS measurement technology can meet PS-18 RA requirements (see Docket Nos. EPA-HQOAR-2013-0696-0030 and 0031). For HCl emission limits equal to or less than 1 ppm, RA is 

measured nearer the quantitation limit of current instrument technology, and an alternative RA 

acceptance criterion similar to that in PS-2 of 40 CFR part 60, appendix B may be applicable. 

Therefore, we have revised the alternative criterion for RA in section 13.4 of PS-18 to allow, 

where the average RM level during the test is less than 75 percent of the applicable emission 

limit, substitution of the equivalent emission limit in parts per million by volume wet (ppmvw) in 

the denominator of the equation for calculating RA. Note that this revision applies to both PS-18 

and section 6 of Procedure 6. 

V. Statutory and Executive Order Reviews 

A. Executive Order 12866: Regulatory Planning and Review and Executive Order 13563: 

Improving Regulation and Regulatory Review 
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This action is not a significant regulatory action and was, therefore, not submitted to the Office 

of Management and Budget (OMB) for review. 

B. Paperwork Reduction Act (PRA) 

This action does not impose an information collection burden under the PRA. This action 

provides performance criteria and QA test procedures for assessing the acceptability of HCl 

CEMS performance and data quality. These criteria and QA test procedures do not add 

information collection requirements beyond those currently required under the applicable 

regulation. 

C. Regulatory Flexibility Act (RFA) 

I certify that this action will not have a significant economic impact on a substantial 

number of small entities under the RFA. This action will not impose any requirements on small 

entities. This action provides facilities with an alternative to PS-15 and FTIRs for measuring HCl 

which is currently required in several rules. 

D. Unfunded Mandates Reform Act (UMRA) 

This action does not contain any unfunded mandate as described in UMRA, 2 U.S.C. 

1531–1538, and does not significantly or uniquely affect small governments. The action imposes 

no enforceable duty on any state, local or tribal governments or the private sector.

E. Executive Order 13132: Federalism 

This action does not have federalism implications. It will not have substantial direct 

effects on the states, on the relationship between the national government and the states, or on 

the distribution of power and responsibilities among the various levels of government. 

F. Executive Order 13175: Consultation and Coordination with Indian Tribal Governments 
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This action does not have tribal implications as specified in Executive Order 13175. This 

action finalizes performance specifications that can be used as an additional option to PS-15 for 

HCl continuous emissions monitoring. Thus, Executive Order 13175 does not apply to this 

action. 

G. Executive Order 13045: Protection of Children from Environmental Health Risks and Safety 

Risks 

 The EPA interprets Executive Order 13045 as applying only to those regulatory actions 

that concern environmental health or safety risks that the EPA has reason to believe may 

disproportionately affect children, per the definition of “covered regulatory action” in section 2-

202 of the Executive Order. This action is not subject to Executive Order 13045 because it does 

not concern an environmental health risk or safety risk. 

H. Executive Order 13211: Actions Concerning Regulations That Significantly Affect Energy 

Supply, Distribution, or Use 

 This action is not subject to Executive Order 13211, because it is not a significant 

regulatory action under Executive Order 12866. 

I. National Technology Transfer and Advancement Act (NTTAA) 

 This rulemaking does not involve technical standards. 

J. Executive Order 12898: Federal Actions to Address Environmental Justice in Minority 

Populations and Low-Income Populations 

 The EPA believes that this action will not have disproportionately high and adverse 

human health or environmental effects on minority or low-income populations because it does 

not affect the level of protection provided to human health or the environment. This action will 

help to ensure that emission control devices are operated properly and maintained as needed, 
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thereby helping to ensure compliance with emission standards, which would benefit all affected 

populations. 

K. Congressional Review Act (CRA) 

This action is subject to the CRA, and the EPA will submit a rule report to each House of 

the Congress and to the Comptroller General of the United States. This action is not a “major 

rule” as defined by 5 U.S.C. 804(2). 

 
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Performance Specification 18 – Performance Specifications and Test Procedures for 

Hydrogen Chloride Continuous Emission Monitoring Systems at Stationary Sources 

List of Subjects in 40 CFR Part 60 

Environmental protection, Administrative practice and procedure, Air pollution control, 

Continuous emission monitoring systems, Hydrogen chloride, Performance specifications, Test 

methods and procedures. 

_______________ 

Dated: 

__________________________________________ 

Gina McCarthy, 

Administrator. 

 
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Part 60, chapter I, title 40 of the Code of Federal Regulations is amended as follows: 

PART 60–STANDARDS OF PERFORMANCE FOR NEW STATIONARY SOURCES 

1. The authority citation for part 60 continues to read as follows: 

Authority: 42 U.S.C. 7401 et seq. 

2. Appendix B to part 60 is amended by adding “Performance Specification 18—

Performance Specifications and Test Procedures for Gaseous Hydrogen Chloride (HCI) 

Continuous Emission Monitoring Systems at Stationary Sources” to read as follows: 

Appendix B to Part 60--Performance Specifications 

* * * * * 

Performance Specification 18--Performance Specifications and Test Procedures for Gaseous 

Hydrogen Chloride (HCI) Continuous Emission Monitoring Systems at Stationary Sources 

1.0 Scope and Application. 

1.1 Analyte. This performance specification (PS) is applicable for measuring gaseous 

concentrations of hydrogen chloride (HCl), CAS: 7647-01-0, on a continuous basis in the units 

of the applicable standard or in units that can be converted to units of the applicable standard(s). 

1.2 Applicability. 

1.2.1 This specification is used to evaluate the acceptability of HCl continuous 

emission monitoring systems (CEMS) at the time of installation or soon after and whenever 

specified in the regulations. The specification includes requirements for initial acceptance 

including instrument accuracy and stability assessments and use of audit samples if they are 

available. 
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1.2.2 The Administrator may require the operator, under section 114 of the Clean Air 

Act, to conduct CEMS performance evaluations at other times besides the initial test to evaluate 

the CEMS performance. See 40 CFR part 60, §§ 60.13(c) and 63.8(e)(1). 

1.2.3 A source that demonstrates their CEMS meets the criteria of this PS may use 

the system to continuously monitor gaseous HCl under any regulation or permit that requires 

compliance with this PS. If your CEMS is capable of reporting the HCl concentration in the units 

of the applicable standard, no additional CEMS components are necessary. If your CEMS does 

not report concentrations in the units of the existing standard, then other CEMS components 

(e.g., oxygen (O2), temperature, stack gas flow, moisture and pressure) may be necessary to 

convert the units reported by your CEMS to the units of the standard. 

1.2.4 These specification test results are intended to be valid for the life of the 

system. As a result, the HCl measurement system must be tested and operated in a configuration 

consistent with the configuration that will be used for ongoing continuous emissions monitoring. 

1.2.5 Substantive changes to the system configuration require retesting according to 

this PS. Examples of such conditions include, but are not limited to: major changes in dilution 

ratio (for dilution based systems); changes in sample conditioning and transport, if used, such as 

filtering device design or materials; changes in probe design or configuration and changes in 

materials of construction. Changes consistent with instrument manufacturer upgrade that fall 

under manufacturer’s certification do not require additional field verification. Manufacturer’s 

upgrades require recertification by the manufacturer for those requirements allowed by this PS, 

including interference, level of detection (LOD), and light intensity qualification. 

1.2.6 This specification is not designed to evaluate the ongoing CEMS performance 

nor does it identify specific calibration techniques and auxiliary procedures to assess CEMS 
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performance over an extended period of time. The requirements in appendix F, Procedure 6 are 

designed to provide a way to assess CEMS performance over an extended period of time. The 

source owner or operator is responsible to calibrate, maintain, and operate the CEMS properly. 

2.0 Summary of Performance Specification. 

2.1 This specification covers the procedures that each CEMS must meet during the 

performance evaluation test. Installation and measurement location specifications, data reduction 

procedures, and performance criteria are included. 

2.2 The technology used to measure gaseous HCl must provide a distinct response 

and address any appropriate interference correction(s). It must accurately measure gaseous HCl 

in a representative sample (path or point sampling) of stack effluent. 

2.3 The relative accuracy (RA) must be established against a reference method (RM) 

(i.e., Method 26A, Method 320, ASTM International (ASTM) D6348-12, including mandatory 

annexes, or Method 321, as appropriate for the source concentration and category). Method 26 

may be approved as a RM by the Administrator on a case-by-case basis if not otherwise allowed 

or denied in an applicable subpart of the regulations. 

2.4 A standard addition (SA) procedure using a reference standard is included in 

appendix A to this performance specification for use in verifying LOD. For extractive CEMS, 

where the SA is done by dynamic spiking (DS), the appendix A procedure is allowed as an 

option for assessing calibration drift and is also referenced by Procedure 6 of appendix F to this 

part for ongoing quality control tests. 

3.0 Definitions. 

3.1 Calibration Cell means a gas containment cell used with cross stack or integrated 

path (IP) CEMS for calibration and to perform many of the test procedures required by this 
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performance specification. The cell may be a removable sealed cell or an evacuated and/or 

purged cell capable of exchanging reference and other calibration gases as well as zero gas 

standards. When charged, it contains a known concentration of HCl and/or interference gases. 

The calibration cell is filled with zero gas or removed from the optical path during stack gas 

measurement. 

3.2 Calibration Drift (CD) means the absolute value of the difference between the 

CEMS output response and an upscale reference gas or a zero-level gas, expressed as a 

percentage of the span value, when the CEMS is challenged after a stated period of operation 

during which no unscheduled adjustments, maintenance or repairs took place. 

3.3 Centroidal Area means a central area that is geometrically similar to the stack or 

duct cross section and is no greater than 10 percent of the stack or duct cross-sectional area. 

3.4 Continuous Emission Monitoring System (CEMS) means the total equipment 

required to measure the pollutant concentration or emission rate continuously. The system 

generally consists of the following three major subsystems: 

3.4.1 Sample Interface means that portion of the CEMS used for one or more of the 

following: sample acquisition, sample transport, sample conditioning, defining the optical 

measurement path, and protection of the monitor from the effects of the stack effluent. 

3.4.2 HCl Analyzer means that portion of the HCl CEMS that measures the total 

vapor phase HCl concentration and generates a proportional output. 

3.4.3 Data Recorder means that portion of the CEMS that provides a permanent 

electronic record of the analyzer output. The data recorder may record other pertinent data such 

as effluent flow rates, various instrument temperatures or abnormal CEMS operation. The data 

recorder may also include automatic data reduction capabilities and CEMS control capabilities. 
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3.5 Diluent Gas means a major gaseous constituent in a gaseous pollutant mixture. 

For combustion sources, either carbon dioxide (CO2) or oxygen (O2) or a combination of these 

two gases are the major gaseous diluents of interest. 

3.6 Dynamic Spiking (DS) means the procedure where a known concentration of HCl 

gas is injected into the probe sample gas stream for extractive CEMS at a known flow rate to 

assess the performance of the measurement system in the presence of potential interference from 

the flue gas sample matrix. 

3.7 Independent Measurement(s) means the series of CEMS data values taken during 

sample gas analysis separated by two times the procedure specific response time (RT) of the 

CEMS. 

3.8 Integrated Path CEMS (IP-CEMS) means an in-situ CEMS that measures the gas 

concentration along an optical path in the stack or duct cross section. 

3.9 Interference means a compound or material in the sample matrix other than HCl 

whose characteristics may bias the CEMS measurement (positively or negatively). The 

interference may not prevent the sample measurement, but could increase the analytical 

uncertainty in the measured HCl concentration through reaction with HCl or by changing the 

electronic signal generated during HCl measurement. 

3.10 Interference Test means the test to detect CEMS responses to interferences that 

are not adequately accounted for in the calibration procedure and may cause measurement bias. 

3.11 Level of Detection (LOD) means the lowest level of pollutant that the CEMS can 

detect in the presence of the source gas matrix interferents with 99 percent confidence. 
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3.12 Liquid Evaporative Standard means a reference gas produced by vaporizing 

National Institute of Standards and Technology (NIST) traceable liquid standards of known HCl 

concentration and quantitatively diluting the resultant vapor with a carrier gas. 

3.13 Measurement Error (ME) is the mean difference between the concentration 

measured by the CEMS and the known concentration of a reference gas standard, divided by the 

span, when the entire CEMS, including the sampling interface, is challenged. 

3.14 Optical Path means the route light travels from the light source to the receiver 

used to make sample measurements. 

3.15 Path Length means, for an extractive optical CEMS, the distance in meters of the 

optical path within a gas measurement cell. For an IP-CEMS, path length means the distance in 

meters of the optical path that passes through the source gas in the stack or duct. 

3.16 Point CEMS means a CEMS that measures the source gas concentration, either at 

a single point at the sampling probe tip or over a path length for IP-CEMS less than 10 percent of 

the equivalent diameter of the stack or duct cross section. 

3.17 Stack Pressure Measurement Device means a NIST-traceable gauge or monitor 

that measures absolute pressure and conforms to the design requirements of ASME B40.100-

2010, “Pressure Gauges and Gauge Attachments” (incorporated by reference – see §60.17). 

3.18 Reference Gas Standard means a NIST-traceable gas standard containing a known 

concentration of HCl certified in accordance with an EPA traceability protocol in section 7.1 of 

this PS. 

3.19 Relative Accuracy (RA) means the absolute mean difference between the gas 

concentration or the emission rate determined by the CEMS and the value determined by the 
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RM, plus the confidence coefficient of a series of nine test runs, divided by the average of the 

RM or the applicable emission standard. 

3.20 Response Time (RT) means the time it takes for the measurement system, while 

operating normally at its target sample flow rate, dilution ratio, or data collection rate to respond 

to a known step change in gas concentration, either from a low- or zero-level to a high-level gas 

concentration or from a high-level to a low or zero-level gas concentration, and to read 95 

percent of the change to the stable instrument response. There may be several response times 

(RTs) for an instrument related to different functions or procedures (e.g., DS, LOD, and ME).

3.21 Span Value means an HCl concentration approximately equal to two times the 

concentration equivalent to the emission standard unless otherwise specified in the applicable 

regulation, permit or other requirement. Unless otherwise specified, the span may be rounded up 

to the nearest multiple of 5. 

3.22 Standard Addition means the addition of known amounts of HCl gas (either 

statically or dynamically) to the actual measurement path or measured sample gas stream. 

3.23 Zero gas means a gas or liquid with an HCl concentration that is below the LOD 

of the measurement system.

4.0 Interferences. 

Sample gas interferences will vary depending on the instrument or technology used to 

make the measurement. Interferences must be evaluated through the interference test in this PS.

Several compounds including carbon dioxide (CO2), carbon monoxide (CO), formaldehyde 

(CH2O), methane (CH4), and water (H2O) are potential optical interferences with certain types of 

HCl monitoring technology. Ammonia is a potential chemical interference with HCl. 

5.0 Safety.
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The procedures required under this PS may involve hazardous materials, operations, and 

equipment. This PS may not address all of the safety issues associated with these procedures. It 

is the responsibility of the user to establish appropriate safety and health practices and determine 

the applicable regulatory limitations prior to performing these procedures. The CEMS user's 

manual and materials recommended by the RM should be consulted for specific precautions to 

be taken. 

6.0 Equipment and Supplies.

Equipment and supplies for CEMS will vary depending on the measurement technology 

and equipment vendors. This section provides a description of the equipment and supplies 

typically found in one or more types of CEMS.

6.1 Sample Extraction System. The portion of an extractive CEMS that collects and 

transports the sample to the pressure regulation and sample conditioning module. The extraction 

system must deliver a representative sample to the measurement instrument. The sample 

extraction system typically consists of a sample probe and a heated umbilical line. 

6.2 Sample Conditioning Module. The portion of an extractive CEMS that removes 

particulate matter and moisture from the gas stream and provides a sample gas stream to the 

CEMS analysis module or analyzer. You must keep the particle-free gas sample above the dew 

point temperature of its components. 

6.3 HCl Analyzer. The portion of the CEMS that detects, quantifies and generates an 

output proportional to the sample gas HCl concentration. 

6.4 System Controller. The portion of the CEMS that provides control of the analyzer 

and other sub-systems (e.g., sample extraction, sample conditioning, reference gas) as necessary 

for continuous operation and periodic maintenance/QC activities. 
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6.5 Data Recorder. The portion of the CEMS that provides a record of analyzer 

output. The data recorder may record other pertinent data such as effluent flow rates, various 

instrument temperatures or abnormal CEMS operation. The data recorder output range must 

include the full range of expected HCl concentration values in the gas stream to be sampled 

including zero and span value. 

6.6 Reference Gas System(s). Gas handling system(s) needed to introduce reference 

and other gases into the measurement system. For extractive CEMS, the system must be able to 

introduce gas flow sufficient to flood the sampling probe and prevent entry of gas from the 

effluent stream. For IP-CEMS, the system must be able to introduce a known concentration of 

HCl, at known cell length, pressure and temperature, into the optical path used to measure HCl 

gas concentration. 

6.7 Moisture Measurement System. If correction of the measured HCl emissions for 

moisture is required, you must install, operate, maintain, and quality assure a continuous 

moisture monitoring system for measuring and recording the moisture content of the flue gases. 

The following continuous moisture monitoring systems are acceptable: an FTIR system validated 

according to Method 301 or section 13.0 of Method 320 in appendix A to part 63 of this chapter; 

a continuous moisture sensor; an oxygen analyzer (or analyzers) capable of measuring O2 both 

on a wet basis and on a dry basis; a stack temperature sensor and a moisture look-up table, i.e., a 

psychrometric chart (for saturated gas streams following wet scrubbers or other demonstrably 

saturated gas streams, only); or other continuous moisture measurement methods approved by 

the Administrator. Alternatively, for any type of fuel, you may determine an appropriate sitespecific default moisture value (or values), using measurements made with Method 4—

Determination of Moisture Content In Stack Gases, in appendix A-3 to of this part. If this option 
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is selected, the site-specific moisture default value(s) must represent the fuel(s) or fuel blends 

that are combusted in the unit during normal, stable operation, and must account for any distinct 

difference(s) in the stack gas moisture content associated with different process operating 

conditions. At least nine Method 4 runs are required for determining each site-specific default 

moisture percentage. Calculate each site-specific default moisture value by taking the arithmetic 

average of the Method 4 runs. Each site-specific moisture default value shall be updated 

whenever the current value is non-representative, due to changes in unit or process operation, but 

in any event no less frequently than annually. 

7.0 Reagents and Standards. 

7.1 Reference Gases. Reference gases (e.g., cylinder gases or liquid evaporative 

standards) used to meet the requirements of this PS must be NIST certified or NIST-traceable 

and vendor certified to ±5.0 percent accuracy. HCl cylinder gases must be certified according to 

Reference 5 in section 16 of this PS through a documented unbroken chain of comparisons each 

contributing to the reported uncertainty. Liquid evaporative standards must be certified using the 

gravimetrically-based procedures of the latest version of the EPA Traceability Protocol for 

Qualification and Certification of Evaporative HCl Gas Standards and Humidification of HCl 

Gas Standards from Cylinders (see EPA-HQ-OAR-2013-0696-0026.pdf). 

7.2 Cylinder gas and/or liquid evaporative standards must be used within their 

certification periods.

7.3 High concentration cylinder gas or liquid evaporative HCl standards may be 

diluted for use in this specification. You must document the quantitative introduction of HCl 

standards into the system using Method 205, found in 40 CFR part 51, appendix M, or other 

procedure approved by the Administrator.
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8.0 CEMS Measurement Location Specifications and Pretest Preparation.

8.1 Prior to the start of your initial PS tests, you must ensure that the CEMS is 

installed according to the manufacturer’s specifications and the requirements in this section. You 

may use either point or IP sampling technology.

8.2 CEMS Installation. Install the CEMS at an accessible location where the pollutant 

concentration or emission rate measurements are directly representative of the HCl emissions or 

can be corrected so as to be representative of the total emissions from the affected facility. The 

CEMS need not be installed at the same location as the relative accuracy test location. If you fail 

the RA requirements in this specification due to the CEMS measurement location and a 

satisfactory correction technique cannot be established, the Administrator may require the CEMS 

to be relocated. 

8.2.1 Single point sample gas extraction should be (1) no less than 1.0 m (3.3 ft.) 

from the stack or duct wall or (2) within the centroidal area of the stack or duct cross section. 

8.2.2 IP-CEMS measurements should (1) be conducted totally within the inner area 

bounded by a line 1.0 m (3.3 ft.) from the stack or duct wall, (2) have at least 70 percent of the 

path within the inner 50 percent of the stack or duct cross-sectional area, or (3) be located over 

any part of the centroidal area.

8.2.2.1 You must measure the IP-CEMS path length from the inner flange of the 

sampling ports or the inner end of the instrument insertion into the stack cavity using a laser tape 

measure, mechanical measurement tape, or similar device accurate to ±1.5 mm (0.059 in). 

8.2.2.2 You must ensure that any purge flow used to protect IP-CEMS instrument 

windows from stack gas does not alter the measurement path length. Purge flow of less than or 

equal to 10 percent of the gas velocity in the duct meets this requirement. 
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8.2.3 CEMS and Data Recorder Scale Check. After CEMS installation, record and 

document the measurement range of the HCl CEMS. The CEMS operating range and the range 

of the data recording device must encompass all potential and expected HCl concentrations, 

including the concentration equivalent to the applicable emission limit and the span value. 

9.0 Quality Control. [Reserved] 

10.0 Calibration and Standardization. [Reserved] 

11.0 Performance Specification Test Procedure.

 After completing the CEMS installation, setup and calibration, you must complete the PS 

test procedures in this section. You must perform the following procedures and meet the 

performance requirements for the initial demonstration of your CEMS: 

a. Interference Test; 

b. Beam Intensity Test (IP-CEMS only); 

c. Temperature Verification Procedure (IP-CEMS only); 

d. Pressure Verification Procedure (IP-CEMS only); 

e. Level of Detection Determination; 

f. Response Time Test; 

g. Measurement Error Test; 

h. Calibration Drift Test; and 

i. Relative Accuracy Test. 

11.1 Interference Test 

11.1.1 Prior to its initial use in the field, you must demonstrate that your monitoring 

system meets the performance requirements of the interference test in section 13.5 to verify that 
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the candidate system measures HCl accurately in the presence of common interferences in 

emission matrices. 

11.1.2 Your interference test must be conducted in a controlled environment. The 

equipment you test for interference must include the combination of the analyzer, related 

analysis software, and any sample conditioning equipment (e.g., dilution module, moisture 

removal equipment or other interferent scrubber) used to control interferents.

11.1.3 If you own multiple measurement systems with components of the same make 

and model numbers, you need only perform this interference test on one analyzer and associated 

interference conditioning equipment combination. You may also rely on an interference test 

conducted by the manufacturer or a continuous measurement system integrator on a system 

having components of the same make and model(s) of the system that you use.

11.1.4 Perform the interference check using an HCl reference gas concentration of 

approximately five times the LOD.

11.1.5 Introduce the interference test gases listed in Table 1 in section 17.0 of this 

PS to the analyzer/conditioning system separately or in any combination. The interference test 

gases need not be of reference gas quality. 

11.1.5.1 For extractive CEMS, the interference test gases may be introduced directly 

into the inlet to the analyzer/conditioning system after the probe extension coupling. 

11.1.5.2 For IP-CEMS, the interference test gases may be added with the HCl in a 

calibration cell or separately in a temperature-controlled cell. The effective concentration of the 

gas in the cell must meet the requirements in Table 1 corrected for absolute pressure, temperature 

and the nominal stack sampling path length of the CEMS. 
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11.1.6 The interference test must be performed by combining an HCl reference gas 

with each interference test gas (or gas mixture). You must measure the baseline HCl response, 

followed by the response after adding the interference test gas(es) while maintaining a constant 

HCl concentration. You must perform each interference gas injection and evaluation in triplicate. 

Note: The baseline HCl gas may include interference gases at concentrations typical of ambient 

air (e.g., 21 percent O2, 400 parts per million (ppm) CO2, 2 percent H2O), but these 

concentrations must be brought to the concentrations listed in Table 1 when their interference 

effects are being evaluated. 

11.1.7 You should document the gas volume/rate, temperature, and pressure used to 

conduct the interference test. A gas blending system or manifold may be used. 

11.1.8 Ensure the duration of each interference test is sufficient to condition the HCl 

measurement system surfaces before a stable measurement is obtained. 

11.1.9 Measure the HCl response of the analyzer/sample conditioning system 

combination to the test gases in ppmv. Record the responses and determine the overall 

interference response using Table 2 in section 17.0. 

11.1.10 For each interference gas (or mixture), calculate the mean difference 

(ΔMCavg) between the measurement system responses with and without the interference test 

gas(es) using Equation 1 in section 12.2. Summarize the results following the format contained 

in Table 2 in section 17. 

11.1.11 Calculate the percent interference (I) for the gas runs using Equation 2 in 

section 12.2. 

11.1.12 The total interference response (i.e., the sum of the interference responses of 

all tested gaseous components) must not exceed the criteria set forth in section 13.5 of this PS. 
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11.2 Beam Intensity Test for IP-CEMS 

11.2.1 For IP-CEMS, you must establish the tolerance of your system to beam 

intensity attenuation. 

11.2.1.1 Your beam intensity test may be conducted in either a controlled environment 

or on-site during initial setup and demonstration of your CEMS. 

11.2.1.2 If you have multiple measurement systems with components of the same 

make and model numbers, you need only perform this attenuation check on one system and you 

may also rely on an attenuation test conducted by the manufacturer on a system having 

components of the same make and model(s) of the system that you use. 

11.2.2 Insert one or more neutral density filter(s) or otherwise attenuate the beam 

intensity by a known percentage (e.g., 90 percent of the beam intensity). 

11.2.3 Perform a high-level HCl reference gas measurement. 

11.2.4 Record and report the attenuated beam intensity, the measured HCl calibration 

gas concentration at full beam intensity, the measured HCl gas concentration with attenuated 

beam intensity, and the percent difference between the two HCl measurements with and without 

attenuation of the beam intensity. The percent difference must not exceed the criteria set forth in 

section 13.6 of this PS. 

11.2.5 In the future, you may not operate your IP-CEMS at a beam intensity lower 

than that established based on the attenuation used during this test. However, you may repeat the 

test to establish a lower beam intensity limit or level. 

11.3 Temperature Measurement Verification Procedure for IP-CEMS 

11.3.1 Any measurement instrument or device that is used as a reference in 

verification of temperature measurement must have an accuracy that is traceable to NIST. 
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11.3.2 You must verify the temperature sensor used in IP-CEMS measurements onsite as part of the initial installation and verification procedures. 

11.3.3 Comparison to Calibrated Temperature Measurement Device. 

11.3.3.1 Place the sensor of a calibrated temperature reference device adjacent to the 

sensor used to measure stack temperature for your IP-CEMS. The calibrated temperature 

reference device must satisfy the accuracy requirements specified in Table 3 of this PS. The 

calibrated temperature reference device must also have a range equal to or greater than the range 

of your IP-CEMS temperature sensor. 

11.3.3.2 Allow sufficient time for the response of the calibrated temperature 

reference device to reach equilibrium. With the process and control device operating under 

normal conditions, concurrently record the temperatures measured by your IP-CEMS system 

(Mt) and the calibrated temperature reference device (Vt). You must meet the accuracy 

requirements specified in section 13.7 of this PS. 

11.3.3.3 If your IP-CEMS temperature sensor does not satisfy the accuracy 

requirement of this PS, check all system components and take any corrective action that is 

necessary to achieve the required minimum accuracy. Repeat this verification procedure until the 

accuracy requirement of this specification is satisfied. 

11.4 Pressure Measurement Verification Procedure for IP-CEMS 

11.4.1 For stack pressure measurement verification, you must select a NIST-traceable 

gauge or monitor that conforms to the design requirements of ASME B40.100-2010, “Pressure 

Gauges and Gauge Attachments,” (incorporated by reference – see §60.17) as a reference device. 

11.4.2 As an alternative for a calibrated pressure reference device with NISTtraceable accuracy, you may use a water-in-glass U-tube manometer to verify your IP-CEMS 
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pressure measurement equipment, provided there is also an accurate measurement of absolute 

atmospheric pressure at the manometer location. 

11.4.3 Allow sufficient time for the response of the reference pressure measurement 

device to reach equilibrium. With the process and control device operating under normal 

conditions, concurrently record the pressures measured by your IP-CEMS system (MP) and the 

pressure reference device (Vp). You must meet the accuracy requirements specified in section 

13.8 of this PS. 

11.4.4 If your IP-CEMS pressure sensor does not satisfy the accuracy requirement of 

this PS, check all system components and take any corrective action that is necessary to achieve 

the required minimum accuracy. Repeat this verification procedure until the accuracy 

requirement of this specification is satisfied. 

11.5 Level of Detection Determination 

11.5.1 You must determine the minimum amount of HCl that can be detected above 

the background in a representative gas matrix. 

11.5.2 You must perform the LOD determination in a controlled environment such as 

a laboratory or manufacturer’s facility. 

11.5.3 You must add interference gases listed in Table 1 of this PS to a constant 

concentration of HCl reference gas. 

11.5.3.1 You may not use an effective reference HCl gas concentration greater than five 

times the estimated instrument LOD. 

11.5.3.2 For extractive CEMS, inject the HCl and interferents described in section 

11.1.5 directly into the inlet to the analyzer. 
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11.5.3.3 For IP-CEMS, the HCl and interference test gases may be added to a 

calibration cell or separately in a temperature-controlled cell that is part of the measurement 

path. The effective concentration of the gas in the cell must meet the requirements in Table 1 

corrected for absolute pressure, temperature and the nominal stack sampling path length of the 

CEMS. 

11.5.4 Collect seven or more consecutive measurements separated by twice the RT 

(described in section 11.6) to determine the LOD. 

11.5.5 Calculate the standard deviation of the measured values and define the LOD as 

three times the standard deviation of these measurements. 

11.5.5.1 The LOD for extractive units must be determined and reported in ppmv. 

11.5.5.2 The LOD for IP units must be determined and reported on a ppm-meter 

basis and the site- or installation-specific LOD must be calculated based on the actual 

measurement path length and gas density of the emissions at the specific site installation in 

ppmv. 

11.5.6 You must verify the controlled environment LOD of section 11.5.2 of this PS 

for your CEMS during initial setup and field certification testing. You must use the SA 

procedure in appendix A of this PS with the following exceptions: 

11.5.6.1 For the LOD verification in the field, you must make three independent SA 

measurements spiking the native source concentration by no more than three times the controlled 

environment LOD concentration determined in section 11.5.5. 

11.5.6.2 For extractive CEMS, you must perform the SA as a dynamic spike by 

passing the spiked source gas sample through all filters, scrubbers, conditioners and other 

monitoring system components used during normal sampling, and as much of the sampling probe 
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as practical. For IP-CEMS, you must perform the SA procedure by adding or passing a known 

concentration reference gas into a calibration cell in the optical path of the CEMS; you must also 

include the source measurement optical path while performing the SA measurement. 

11.5.6.3 The amount detected, or standard addition response (SAR), is based on the 

average difference of the native HCl concentration in the stack or duct relative to the native stack 

concentration plus the SA. You must be able to detect the effective spike addition (ESA) above 

the native HCl present in the stack gas matrix. For extractive CEMS, the ESA is calculated using 

Equation A7 in appendix A of this PS. For IP-CEMS, the ESA is calculated as Ci,eff using 

Equation 4 of this PS. 

11.5.6.4 For extractive CEMS, calculate the SAR using Equation A4 in appendix A 

of this PS. For IP-CEMS, calculate the SAR using Equation A8. 

11.5.6.5 If your system LOD field verification does not demonstrate a SAR greater 

than or equal to your initial controlled environment LOD, you must increase the SA 

concentration incrementally and repeat the field verification procedure until the SAR is equal to 

or greater than LOD. The site-specific standard addition detection level (SADL) is equal to the 

standard addition needed to achieve the acceptable SAR, and SADL replaces the controlled 

environment LOD. For extractive CEMS, the SADL is calculated as the ESA using Equation A7 

in appendix A of this PS. For IP-CEMS, the SADL is the SA calculated using Equation A8 in 

appendix A of this PS. As described in section 13.1 of this PS, the SADL must be less than 20 

percent of the applicable emission limit. 

11.6 Response Time Determination. You must determine ME-, LOD- and SA-RT. 

11.6.1 For ME- or LOD-RT, start the upscale RT determination by injecting zero gas 

into the measurement system as required by the procedures in section 11.7 or 11.5, respectively. 
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You may use humidified zero gas. For standard addition RT, start the upscale RT determination 

by measuring the native stack gas concentration of HCl. 

11.6.1.1 For extractive CEMS measuring ME- or LOD-RT, the output has stabilized 

when there is no change greater than 1.0 percent of full scale for 30 seconds. 

11.6.1.2 For standard addition RT that includes the stack gas matrix the final stable 

response may continue to vary by more than 1 percent, but may be considered stable if the 

variability is random and not continuously rising or falling. 

11.6.2 When the CEMS output has stabilized, record the response in ppmv and 

introduce an upscale (high level) or spike reference gas as required by the relevant procedure. 

11.6.3 Record the time (upscale RT) required to reach 95 percent of the change to the 

final stable value. 

11.6.4 Next, for ME or LOD RT, reintroduce the zero gas and record the time 

required to reach 95 percent of the change to the stable instrument response at the zero gas 

reading. For SA RT, introduce zero gas to the IP-CEMS cell or stop the spike gas flow to the 

extractive CEMS as required by the specified procedure and record the time required to reach 95 

percent of the change to the stable instrument response of the native gas reading. This time is the 

downscale RT. 

(Note: For CEMS that perform a series of operations (purge, blow back, sample integration, 

analyze, etc.), you must start adding reference or zero gas immediately after these procedures are 

complete.) 

11.6.5 Repeat the entire procedure until you have three sets of data, then determine 

the mean upscale and mean downscale RTs for each relevant procedure. Report the greater of the 

average upscale or average downscale RTs as the RT for the system. 
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11.7 Measurement Error (ME) Test. 

11.7.1 On the same day and as close in time as practicable to when the ME test is 

conducted, perform and meet requirements for a calibration drift (CD) test using a zero gas as 

used in the Seven-Day Drift Test (see section 11.8) and document and report the results. To meet 

this requirement, the ME test may be conducted during the Seven-Day CD Test. 

11.7.2 Extractive CEMS ME Test. 

11.7.2.1 Introduce reference gases to the CEMS probe, prior to the sample conditioning 

and filtration system. 

11.7.2.2 Measure three upscale HCl reference gas concentrations in the range shown in 

Table 4 of this PS. 

11.7.2.3 Introduce the gases into the sampling probe with sufficient flow rate to replace 

the entire source gas sample. 

11.7.2.4 Continue to add the reference gas until the response is stable as evidenced when 

the difference between two consecutive measurements is less than the LOD or within five 

percent of each other. 

11.7.2.5 Make triplicate measurements for each reference gas for a total of nine 

measurements. Introduce different reference gas concentrations in any order but do not introduce 

the same gas concentration twice in succession. 

11.7.2.6 At each reference gas concentration, determine the average of the three CEMS 

responses (ܥܯప തതതതത). Calculate the ME using Equation 3A in section 12.3. 

11.7.2.7 If you desire to determine the system RT during this test, you must inject zero 

gas immediately before and after each injection of the high-level gas standard. 
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11.7.2.8 For non-dilution systems, you may adjust the system to maintain the correct 

flow rate at the analyzer during the test, but you may not make adjustments for any other 

purpose. For dilution systems, you must operate the measurement system at the appropriate 

dilution ratio during all system ME checks, and you may make only the adjustments necessary to 

maintain the proper ratio. 

11.7.3 IP-CEMS ME Test 

11.7.3.1 Conduct a 3-level system ME test by individually adding the known 

concentrations of HCl reference gases into a calibration cell of known volume, temperature, 

pressure and path length. 

Note: The optical path used for IP-CEMS ME checks must include the native HCl measurement 

path. You must also collect native stack concentration HCl measurements before and after each 

HCl standard measurement. Bracketing HCl reference gas measurements with native stack HCl 

measurements must be used in the calculations in Equation 5 in section 12.4.2 to correct the 

upscale measurements for stack gas HCl concentration changes. 

11.7.3.2 Introduce HCl reference gas into your calibration cell in a range of 

concentrations that produce responses equivalent to the source concentrations shown in Table 4 

of this PS for your path length. 

11.7.3.3 Make triplicate measurements for each reference gas standard for a total of nine 

measurements. Introduce different calibration concentrations in any order but do not introduce 

the same reference gas concentration twice in succession. 

11.7.3.4 You must calculate the effective concentration (Ci,eff) of the HCl reference gas 

equivalent to the stack concentration by correcting for calibration cell temperature, pressure, path 
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length, line strength factor (LSF) and, if necessary, the native stack gas HCl concentration using 

Equation 4 in section 12.0. 

11.7.3.5 You may use the LSF provided by your instrument manufacturer or determine 

an instrument-specific LSF as a function of temperature using a heated gas cell and equivalent 

concentrations (Ci,eff) between 50 and 150 percent of the emission limit. 

11.7.3.6 At each reference gas concentration, average the three independent CEMS 

measurement responses corrected for native HCl stack concentration. Calculate the ME using 

Equation 6A in section 12.4.3. 

11.7.4 You may use Figure 1 in section 17.0 to record and report your ME test 

results. 

11.7.5 If the ME specification in section 13.3 is not met for all three reference gas 

concentrations, take corrective action and repeat the test until an acceptable 3-level ME test is 

achieved. 

11.8 Seven-Day Calibration Drift (CD) Test 

11.8.1 The CD Test Period. Prior to the start of the RA tests, you must perform a 

seven-day CD test. The purpose of the seven-day CD test is to verify the ability of the CEMS to 

maintain calibration for each of seven consecutive unit operating days as specified in section 

11.8.5 of this PS. 

11.8.2 The CD tests must be performed using the zero gas and mid-level reference 

gas standards as defined in Table 4 of this PS. 

11.8.3 Conduct the CD test on each day during continuous operation of the CEMS 

and normal facility operations following the procedures in section 11.7 of this PS, except that the 

zero gas and mid-level gas need only be introduced to the measurement system once each. 
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11.8.4 If periodic automatic or manual adjustments are made to the CEMS zero and 

upscale response factor settings, conduct the CD test immediately before these adjustments. 

Note: Automatic signal or mathematical processing of all measurement data to determine 

emission results may be performed throughout the entire CD process. 

11.8.5 Determine the magnitude of the CD at approximately 24-hour intervals, for 7 

consecutive unit operating days. The 7 consecutive unit operating days need not be 7 consecutive 

calendar days. 

11.8.6 Record the CEMS response for single measurements of zero gas and mid-level 

reference gas. You may use Figure 2 in section 17 of this PS to record and report the results of 

your 7-day CD test. 

11.8.6.1 For extractive CEMS, calculate the CD using Equation 3B in section 12.3. 

Report the absolute value of the differences as a percentage of the span value. 

11.8.6.2 For IP-CEMS, you must include the source measurement optical path while 

performing the upscale CD measurement; you must exclude the source measurement optical path 

when determining the zero gas concentration. Calculate the CD for IP CEMS using Equations 4, 

5, 6B, and 7 in section 12.4. 

11.8.7 The zero-level and mid-level CD for each day must be less than 5.0 percent of 

the span value as specified in section 13.2 of this PS. You must meet this criterion for 7 

consecutive operating days past the 7-day CD test. 

11.8.8 Dynamic Spiking Option for Seven-Day CD Test. For extractive CEMS, you 

have the option to conduct a mid-level dynamic spiking procedure for each of the 7 days in lieu 

of the mid-level reference gas injection described in sections 11.8.2 and 11.8.3. If this option is 

selected, the daily zero CD check is still required. 
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11.8.8.1 To conduct each of the seven daily mid-level dynamic spikes, you must use the 

DS procedure described in appendix A of this PS using a single spike of the mid-level reference 

gas (see Table 4). 

11.8.8.2 You must perform the dynamic spike procedure by passing the spiked source 

gas sample through all filters, scrubbers, conditioners and other monitoring system components 

used during normal sampling, and as much of the sampling probe as practical. 

11.8.8.3 Calculate the mid-level CD as a percent of span using Equation A6 of appendix 

A to this PS and calculate the zero drift using Equation 3B in section 12.3. Record and report the 

results as described in sections 11.8.6 and 11.8.7. 

11.9 Relative Accuracy Test 

11.9.1 Unless otherwise specified in an applicable regulation, use Method 26A in 40 

CFR part 60, appendix A-8, Method 320 or Method 321, both found in 40 CFR part 63, appendix 

A, or ASTM D6348-12 including all annexes, as applicable, as the RMs for HCl measurement. 

Obtain and analyze RM audit samples, if they are available, concurrently with RM test samples 

according to the same procedure specified for performance tests in the general provisions of the 

applicable part. If Method 26 is not specified in an applicable subpart of the regulations, you may 

request approval to use Method 26 in appendix A-8 to this part as the RM on a site-specific basis 

under §§63.7(f) or 60.8(b). Other RMs for moisture, O2, etc., may be necessary. Conduct the RM 

tests in such a way that they will yield results representative of the emissions from the source and 

can be compared to the CEMS data. 

11.9.1.1 When Method 26A is used as the RM, you must sample sufficient gas to reach 

three times your method detection limit for Method 26A in 40 CFR part 60, appendix A-8, or for 

a minimum of one hour, whichever is greater. 
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11.9.1.2 When Method 320 or Method 321, both found in 40 CFR part 63, 

appendix A, or ASTM D6348-12, are used as the RM, you must collect gas samples that are at 

stack conditions (hot and wet) and you must traverse as required in section 11.9.3. 

11.9.2 Conduct the diluent (if applicable), moisture (if needed), and pollutant 

measurements simultaneously. However, diluent and moisture measurements that are taken 

within an hour of the pollutant measurements may be used to calculate dry pollutant 

concentration and emission rates. 

11.9.3 Reference Method Measurement Location and Traverse Point(s) Selection.

11.9.3.1 Measurement Location. Select, as appropriate, an accessible RM measurement 

location at least two equivalent diameters downstream from the nearest control device, point of 

pollutant generation, or other point at which a change in the pollutant concentration or emission 

rate may occur, and at least one half equivalent diameter upstream from the effluent exhaust or a 

control device. When pollutant concentration changes are due solely to diluent leakage (e.g., air 

heater leakages) and pollutants and diluents are simultaneously measured at the same location, a 

half diameter may be used in lieu of two equivalent diameters. The equivalent duct diameter is 

calculated according to Method 1 in appendix A-1 to this part. The CEMS and RM sampling 

locations need not be the same. 

11.9.3.2 Traverse Point Selection. Select traverse points that assure acquisition of 

representative RM samples over the stack or duct cross section according to one of the following 

options: (a) sample at twelve traverse points located according to section 11.3 of Method 1 in 

appendix A-1 to this part, (b) sample at 6 Method 1 traverse points according to section 

6.5.6(b)(1) of appendix A to part 75 of this chapter, or (c) sample at three points on a 

measurement line (“3-point long line”) that passes through the centroidal area of the duct in the 
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direction of any potential stratification. If this line interferes with the CEMS measurements, you 

may displace the line up to 20 cm (12 in.) or 5.0 percent of the equivalent diameter of the cross 

section, whichever is less, from the centroidal area. Locate the three traverse points at 16.7, 50.0, 

and 83.3 percent of the measurement line. Alternatively, you may conduct a stratification test 

following the procedures in sections 11.9.3.2.1 through 11.9.3.2.4 to justify sampling at a single 

point or three points located on the measurement line at 0.4, 1.2, and 2.0 m from the stack wall 

(“3-point short line”). Stratification testing must be conducted at the sampling location to be used 

for the RM measurements during the RA test and must be made during normal facility operating 

conditions. You must evaluate the stratification by measuring the gas on the same moisture basis 

as the HCl CEMS (wet or dry). Stratification testing must be repeated for each RA test program 

to justify single point or “3-point short line” sampling. 

11.9.3.2.1 Use a probe of appropriate length to measure the HCl concentration or 

an alternative analyte, as described in this section, using 12 traverse points located according to 

section 11.3 of Method 1 in appendix A-1 to 40 CFR part 60 for a circular stack or nine points at 

the centroids of similarly-shaped, equal area divisions of the cross section of a rectangular stack. 

11.9.3.2.2 You may substitute a stratification test for SO2 for the HCl stratification 

test. If you select this option, you must follow the test procedures in Method 6C of appendix A-4 

to 40 CFR part 60 or Method 320 of appendix A of 40 CFR part 63. 

11.9.3.2.3 Calculate the mean measured concentration for all sampling points 

(MNavg). 

11.9.3.2.4 Calculate the percent stratification (St) of each traverse point using 

Equation 8 in section 12.5. 
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11.9.3.2.5 The gas stream is considered to be unstratified and you may perform the 

RA testing at a single point that most closely matches the mean if the concentration at each 

traverse point differs from the mean concentration for all traverse points by: (a) no more than 

5.0 percent of the mean concentration; or (b) 0.2 ppm (for HCl) or 3 ppm (for SO2) absolute, 

whichever is less restrictive. 

11.9.3.2.6 If the criterion for single point sampling (5.0 percent, 0.2 ppm for HCl 

or 3 ppm for SO2 are not met, but the concentration at each traverse point differs from the mean 

concentration for all traverse points by no more than 10.0 percent of the mean, the gas stream is 

considered to be minimally stratified, and you may take RA samples using the “3-point short 

line”. Alternatively, you may use the 3-point short line if each traverse point differs from the 

mean value by no more than 0.4 ppm (for HCl) or 5 ppm (for SO2). 

11.9.3.2.7 If the concentration at any traverse point differs from the mean 

concentration by more than 10 percent, the gas stream is considered stratified and you must 

sample using one of the options in section 11.9.3.2 above. 

11.9.3.3 Conduct all necessary RM tests within 3 cm (1.2 in.) of the traverse points, 

but no closer than 3 cm (1.2 in.) to the stack or duct wall. 

11.9.4 In order to correlate the CEMS and RM data properly, record the beginning and 

end of each RM run (including the time of day in hours, minutes, and seconds) using a clock 

synchronized with the CEM clock used to create a permanent time record with the CEMS output. 

11.9.5 You must conduct the RATA during representative process and control 

operating conditions or as specified in an applicable regulation, permit or subpart. 

11.9.6 Conduct a minimum of nine RM test runs. NOTE: More than nine RM test 

runs may be performed. If this option is chosen, up to three test run results may be excluded so 
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long as the total number of test run results used to determine the CEMS RA is greater than or 

equal to nine. However, all data must be reported including the excluded test runs. 

11.9.7 Analyze the results from the RM test runs using Equations 9 – 14 in section 

12.6. Calculate the RA between the CEMS results and the RM. 

11.10 Record Keeping and Reporting 

11.10.1 For systems that use a liquid evaporative standard generator to deliver HCl 

reference gas standards, record supporting data for these devices, including liquid feed 

calibrations, liquid standard concentration(s) and NIST-traceability, feed rate and gas flow 

calibrations for all diluent and HCl gas flows. All calibrations must include a stated uncertainty, 

and the combined uncertainty of the delivered HCl reference gas concentration must be 

calculated and reported. 

11.10.2 Record the results of the CD test, the RT test, the ME test, the RA test, and 

for IP-CEMS, the results of the beam intensity, temperature and pressure verification procedures. 

Also keep records of the RM and CEMS field data, calculations, and reference gas certifications 

necessary to confirm that the performance of the CEMS met the performance specifications. 

11.10.3 For systems that use Method 205 to prepare HCl reference gas standards, 

record results of Method 205 performance test field evaluation, reference gas certifications, and 

gas dilution system calibration. 

11.10.4 Record the LOD for the CEMS. For extractive CEMS, record the LOD in 

ppmv. For IP-CEMS, record the LOD on a ppm-meter basis along with a calculation of the 

installation specific LOD in ppmv. For both CEMS types, you must also record the field verified 

SADL.

11.10.5 Record the results of the interference test. 
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11.10.6 Report the results of all certification tests to the appropriate regulatory 

agency (or agencies), in hardcopy and/or electronic format, as required by the applicable 

regulation or permit. 

12.0 Calculations and Data Analysis. 

12.1 Nomenclature 

Ci = Zero HCl reference gas concentration used for test i (ppmv);

Ci,eff = Equivalent concentration of the reference gas value, Ci, at the specified 

conditions (ppmv);

CC = Confidence coefficient (ppmv); 

CDextractive = Calibration drift for extractive CEMS (percent); 

CDIP = Calibration drift for IP-CEMS (percent); 

CD0 = Calibration drift at zero HCl concentrations for an IP-CEMS (percent); 

davg = Mean difference between CEMS response and the reference gas (ppmv); 

di = Difference of CEMS response and the RM value (ppmv); 

I = Total interference from major matrix stack gases, (percent); 

LSF = Line strength factor for IP-CEMS instrument specific correction for temperature 

and gas matrix effects derived from the HITRAN and/or manufacturer specific 

database (unitless); 

ΔMCavg = Average of the 3 absolute values of the difference between the measured HCl 

reference gas concentrations with and without interference from selected stack 

gases (ppmv); 

MCi = Measured zero or HCl reference gas concentration i (ppmv); 

ܥܯప തതതതത = Average of the measured zero or HCl reference gas concentration i (ppmv); 
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MCint = Measured HCl concentration of the HCl reference gas plus the individual or 

combined interference gases (ppmv); 

MEextractive = Measurement error for extractive CEMS (percent); 

MEIP = Measurement error for IP-CEMS (percent); 

MNavg = Average concentration at all sampling points (ppmv); 

MNbi = Measured native concentration bracketing each calibration check measurement 

(ppmv); 

MNi = Measured native concentration for test or run i (ppmv); 

n = Number of measurements in an average value; 

PLCell = Path length of IP-CEMS calibration cell (m); 

PLStack = Path length of IP-CEMS stack optical path (m); 

RA = Relative accuracy of CEMS compared to a RM (percent); 

RMi = RM concentration for test run i (ppmv); 

RMavg = Mean measured RM value (ppmv); 

S = Span of the instrument (ppmv); 

Sd = Standard deviation of the differences (ppmv); 

Sti = Stratification at traverse point i (percent); 

SADL = Standard addition detection level (ppmv); 

t0.975 = One-sided t-value at the 97.5th percentile obtained from Table 5 in section 17.0 

for n-1 measurements; 

Treference = Temperature of the calibration cell for IP-CEMS (degrees Kelvin); 

Tstack = Temperature of the stack at the monitoring location for IP-CEM (degrees ``

 Kelvin). 
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12.2 Calculate the difference between the measured HCl concentration with and 

without interferents for each interference gas (or mixture) for your CEMS as: 

ܥܯ߂௔௩௚ ൌ ∑ |ெ஼೔ିெ஼೔೙೟| య

೔సభ

ଷ Eq. 1 

Calculate the total percent interference as: 

ܫ ൌ ∑ ௱ெ஼ೌೡ೒

ெ஼೔

௡

௜ୀଵ ∗ 100 Eq. 2 

12.3 Calculate the ME or CD at concentration i for an extractive CEMS as: 

ܧܯ௘௫௧௥௔௖௧௜௩௘ ൌ |஼೔ିெ஼ഢ തതതതതത|

ௌ

∗ 100 Eq. 3A

ܦܥ௘௫௧௥௔௖௧௜௩௘ ൌ |஼೔ିெ஼೔|

ௌ

	∗ 100 Eq. 3B

12.4 Calculate the ME or CD at concentration i for IP-CEMS that use a calibration 

cell as follows:

12.4.1 Calculate the equivalent concentration Ci,eff using Equation 4:

ൈ௜ ܥ൤ ൌ௘௙௙ ,௜ܥ

௉௅೎೐೗೗

௉௅ೄ೟ೌ೎ೖ

ൈ

்ೞ೟ೌ೎ೖ

்ೝ೐೑೐ೝ೐೙೎೐ ൈ ܮܵܨ൨ Eq. 4

12.4.2 Calculate the average native concentration before and after each calibration 

check measurement as: 

ܯܰ ௜௕ൌ ெே೔ା	ெே೔శభ

ଶ Eq. 5

12.4.3 Calculate the ME or CD at concentration i for an IP-CEMS as:

ܧܯூ௉ ൌ ∑ 	หሺெ஼೔ିெே್೔ሻି஼೔೐೑೑ห య

భ

ଷௌ

∗ 100 Eq. 6A

ܦܥூ௉ ൌ หெ஼೔ିெே್೔ି஼೔,೐೑೑ห

ௌ

∗ 100 Eq. 6B

12.4.4 Calculate the zero CD as a percent of span for an IP-CEMS as:
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ൌ଴ 	 ܦܥ

|ெ஼೔ିெ஼೔శభ|

ௌ

∗ 100 Eq. 7

12.5 Calculate the percent stratification at each traverse point as: 

ܵ௧௜ ൌ หெே೔ି୑୒౗౬ౝห

ெேೌೡ೒

∗ 100 Eq. 8

12.6 Calculate the RA using RM and CEMS data.

12.6.1 Determine the CEMS final integrated minute average pollutant concentration 

or emission rate for each RM test period. Consider system RT, if important, and confirm that the 

results have been corrected to the same moisture, temperature and diluent concentration basis.

12.6.2 When Method 26A (or if approved for use, Method 26), found in 40 CFR part 

60, appendix A-8 of this part, is used as the RM, compare each CEMS integrated average value 

against the corresponding RM value for identical test periods. Make these comparisons on the 

same basis (e.g., wet, dry, ppmv, or units of the standard). To convert results generate by Method 

26A or 26 in mg/DSCM to ppmv, use the conversion factor 0.662 ppm/(mg/DSCM).

12.6.3 If the RM is Method 320 or Method 321, found in 40 CFR part 63, appendix 

A, or ASTM D6348-12, make a direct comparison of the average RM results and CEMS average 

value for identical test periods.

12.6.4 For each test run, calculate the arithmetic difference of the RM and CEMS 

results using Equation 9.

݀௜ ൌ 	 ܴܯ ௜െ ܯܰ ௜Eq. 9 

12.6.5 Calculate the standard deviation of the differences (ܵௗ) of the CEMS 

measured and RM results using Equation 10.

ܵௗ ൌ 	ඨ∑ ቆௗ೔ିቆ

∑ ೏೔ ೙

೔సభ

೙ ቇ	ቇ

మ

೙

೔

௡ିଵ Eq. 10 
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12.6.6 Calculate the confidence coefficient (CC) for the RATA using Equation 11. 

ܥܥ ൌ ݐ଴.ଽ଻ହ ∗ ൬ ௌ೏

൫௡భ/మ൯

൰ Eq. 11

12.6.7 Calculate the mean difference (݀௔௩௚) between the RM and CEMS values in the 

units of ppmv or the emission standard using Equation 12. 

݀௔௩௚ ൌ 	

ଵ

௡ ∑ ݀௜ ௡

௜ୀଵ Eq. 12

12.6.8 Calculate the average RM value using Equation 13. 

ܴܯ௔௩௚ ൌ 	

ଵ

௡ ௜ܯܴ ∑ ௡

௜ୀଵ Eq. 13

12.6.9 Calculate RA of the CEMS using Equation 14. 

ܴܣ ൌ ൣ൫ห݀௔௩௚ห ൅ ܥܥ൯/ܴܯ௔௩௚൧ ∗ 100 Eq. 14

13.0 Method Performance. 

13.1 Level of Detection. You may not use a CEMS whose LOD or SADL is greater 

than 20 percent of the applicable regulatory limit or other action level for the intended use of the 

data. 

13.2 Calibration Drift. The zero- and mid-level calibration drift for the CEMS must 

not exceed 5.0 percent of the span value for 7 consecutive operating days. 

13.3 Measurement Error. The ME must be less than or equal to 5.0 percent of the span 

value at the low-, mid-, and high-level reference gas concentrations. 

13.4 Relative Accuracy. Unless otherwise specified in an applicable regulation or 

permit, the RA of the CEMS, whether calculated in units of HCl concentration or in units of the 

emission standard, must be less than or equal to 20.0 percent of the RM when ܴܯ௔௩௚ is used in 

the denominator of Equation 14. 
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13.4.1 In cases where the RA is calculated on a concentration (ppmv) basis, if the 

average RM emission level for the test is less than 75 percent of the HCl concentration 

equivalent to the emission standard, you may substitute the HCl concentration equivalent to the 

standard in the denominator of Equation 14 in place of. RMavg. 

13.4.2 Similarly, if the RA is calculated in units of the emission standard and the HCl 

emission level measured by the RMs is less than 75 percent of the emission standard, you may 

substitute the emission standard in the denominator of Equation 14 in place of RMavg. 

13.4.3 The alternative calculated RA in paragraph 13.4.1 or 13.4.2 must be less than 

or equal to 15.0 percent. 

13.5 Interference Test. 

13.5.1 The sum of the interference response(s) from Equation 2 must not be greater 

than 2.5 percent of the calibration span or  3.0 percent of the equivalent HCl concentration used 

for the interference test, whichever is less restrictive. The results are also acceptable if the sum of 

the interference response(s) does not exceed six times the LOD or 0.5 ppmv for a calibration 

span of 5 to 10 ppm, or 0.2 ppmv for a calibration span of less than 5 ppmv. 

13.6 IP-CEMS Beam Intensity Test. For IP-CEMS, the percent difference between the 

measured concentration with and without attenuation of the light source must not exceed  3.0 

percent. 

13.7 IP-CEMS Temperature Measurement Verification. Your temperature sensor 

satisfies the accuracy required if the absolute relative difference between measured value of 

stack temperature (Mt) and the temperature value from the calibrated temperature reference 

device (Vt) is ≤ 1.0 percent or if the absolute difference between Mt and Vt is ≤ 2.8C (5.0F), 

whichever is less restrictive. 
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13.8 IP-CEMS Pressure Sensor Measurement Verification. Your pressure sensor 

satisfies the accuracy required if the absolute relative difference between the measured value of 

stack pressure (MP) and the pressure value from the calibrated pressure reference device (VP) is ≤

5.0 percent or if the absolute difference between Mp and VP is ≤ 0.12 kilopascals (0.5 inches of 

water column), whichever is less restrictive. 

14.0 Pollution Prevention. [Reserved] 

15.0 Waste Management. [Reserved] 

16.0 Bibliography. 

1. Method 318—Extractive FTIR Method for the Measurement of Emissions From the Mineral 

Wool and Wool Fiberglass Industries, 40 CFR, part 63, subpart HHHHHHH, appendix A. 

2. "EPA Protocol for the Use of Extractive Fourier Transform Infrared (FTIR) Spectrometry in 

Analyses of Gaseous Emissions from Stationary Industrial Sources," February, 1995. 

3. “Measurement of Gaseous Organic and Inorganic Emissions by Extractive FTIR 

Spectroscopy,” EPA Contract No. 68-D2-0165, Work Assignment 3-08. 

4. “Method 301 - Field Validation of Pollutant Measurement Methods from Various Waste 

Media,” 40 CFR part 63, appendix A. 

5. 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. 

17.0 Tables, Diagrams, Flowcharts, and Validation Data. 

Table 1. Interference Test Gas Concentrations 

Potential Interferent 

Gas1

Approximate Concentration (balance N2) 

CO2 15% ± 1% CO2

2

 
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CO 100 ± 20 ppm 

CH2O 20 ± 5 ppm 

CH4 100 ± 20 ppm 

NH3 10 ± 5 ppm (extractive CEMS only) 

NO2 250 ± 50 ppm 

SO2 200 ± 20 ppm 

O2 3% ± 1% O2

2

 

H2O 10% ± 1% H2O2 

N2 Balance2 

1 Any of these specific gases can be tested at a lower level if the manufacturer has provided 

reliable means for limiting or scrubbing that gas to a specified level in CEMS field installations. 

2 Gases for short path IP cell interference tests cannot be added above 100 percent stack 

equivalent concentration. Add these gases at the indicated percentages to make up the remaining 

cell volume. 

 
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Table 2. Example Interference Test Data Sheet 

Date of Test: ____________________________________________ 

Analyzer Type: ___________________________________________ 

Model No.: _______________________________________________ 

Serial No.: ______________________________________________ 

Span: ____________________________________________________ 

Test Organization: _______________________________________ 

Test Personnel: __________________________________________ 

Interference 

Gas or Gas 

Combination 

HCl 

Concentration 

(ppmv) 

HCl 

Concentration 

(ppmv) 

w/Interference

Absolute 

Difference 

(ppmv) 

Average 

Absolute 

Difference 

(ppmv) 

 

 

 

 

 

 

 

 

 

Sum of Interference Responses 

Percent of Baseline Concentration 

Percent of Span 
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Table 3. Design Standards for Temperature Sensors 

If the sensor is a . . . You can use the following design standards as guidance in 

selecting a sensor for your IP-CEMS 

1. Thermocouple a. ASTM E235–88 (1996), “Specification for Thermocouples, 

Sheathed, Type K, for Nuclear or Other High-Reliability 

Applications.” 

b. ASTM E585/E585M–04, “Specification for Compacted 

Mineral-Insulated, Metal-Sheathed, Base Metal Thermocouple 

Cable.” 

c. ASTM E608/E608M–06, “Specification for MineralInsulated, Metal-Sheathed Base Metal Thermocouples.” 

d. ASTM E696–07, “Specification for Tungsten-Rhenium 

Alloy Thermocouple Wire.” 

e. ASTM E1129/E1129M–98 (2002), “Standard Specification 

for Thermocouple Connectors.” 

f. ASTM E1159–98 (2003), “Specification for Thermocouple 

Materials, Platinum-Rhodium Alloys, and Platinum.” 

g. ISA–MC96.1–1982, “Temperature Measurement 

Thermocouples.” 

2. Resistance temperature 

detector 

ASTM E1137/E1137M–04, “Standard Specification for 

Industrial Platinum Resistance Thermometers.” 

 
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Table 4. Performance Specification Test Zero and Reference Gas Ranges 

 

Test Units 

HCl Zero and Reference Gas 

Concentrations in Terms of Percent of 

Spana Section 

Zero Low 

Level 

Mid 

Level 

High 

Level 

Calibration Drift % of 

Span 

<LOD NA 50 – 60b NA 11.8 

Measurement 

Error 

% of 

Span 

NA 20 – 30 50 - 60 80 – 100 11.7 

a

 Reference gas concentration must be NIST traceable. (see section 7.1) 

b

 Mid-level is required. For DS calibration drift option, choose a concentration that yields a value 

in this range at the analyzer. 

Table 5. Student’s t-Values 

n-1a

 t-value n-1a t-value n-1a t-value 

1 12.71 11 2.201 21 2.080 

2 4.303 12 2.179 22 2.074 

3 3.182 13 2.160 23 2.069 

4 2.776 14 2.145 24 2.064 

5 2.571 15 2.131 25 2.060 

6 2.447 16 2.120 26 2.056 

7 2.365 17 2.110 27 2.052 

8 2.306 18 2.101 28 2.048 

9 2.262 19 2.093 29 2.045 

10 2.228 20 2.086 30 2.042 

a

 The value n is the number of independent pairs of measurements. Either discrete (independent) 

measurements in a single run, or run averages can be used. 

 
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SOURCE: 

DATE: 

CEMS: 

LOCATION: 

SERIAL NUMBER: 

SPAN: 

RUN 

NUMBER 

REFERENCE GAS 

VALUE 

CEMS 

RESPONSE DIFFERENCE 

Low Mid High 

1 

2 

3 

4 

5 

6 

7 

8 

9 

 Mean Difference = 

 Measurement Error = % % %

Figure 1. Measurement Error Determination 

 
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SOURCE: DATE: 

CEMS: LOCATION: 

SERIAL NUMBER: SPAN: 

LEVEL DA

Y 

DAT

E 

TIME REFERENC

E GAS 

VALUE 

 CEMS 

RESPONSE 

DIFFERENCE PERCENT 

OF SPAN 

ZERO GAS 

1 

2 

3 

4 

5 

6 

7 

MID-LEVEL GAS 

1 

2 

3 

4 

5 

6 

7 

Figure 2. Calibration Drift Determination 

 
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PS-18 Appendix A Standard Addition Procedures

1.0 Scope and Application 

1.1 This appendix to Performance Specification (PS) 18 describes the procedure and 

performance requirements for standard addition (SA) as a quality check for hydrogen chloride 

(HCl) continuous emission monitoring systems (CEMS). 

1.2 This appendix is applicable to quality checks of both extractive and integrated 

path (IP) technologies used to measure HCl emissions. 

1.3 For extractive CEMS, this procedure must be used, as a level of detection (LOD) 

verification of all field-installed CEMS. Additionally, it is allowed by Procedure 6 in appendix F 

to this part as an alternative to upscale calibration drift (CD) tests, cylinder gas audits and 

relative accuracy audits (RAAs), and may be used for quality assurance purposes under other 

applicable regulations or permits that require HCl monitoring. 

1.4 For IP-CEMS, this procedure must be used as a LOD verification of all fieldinstalled CEMS. 

2.0 Summary of the Appendix for Standard Addition. 

 As used here, SA is a gas phase method of standard additions (either static or dynamic) 

used to verify the accuracy of CEMS measurements in the presence of the sample matrix. For 

extractive CEMS, it consists of spiking a known quantity of HCl dynamically into the 

measurement system as an addition to the native HCl and the native source gas matrix. For IPCEMS, this procedure consists of introducing a known quantity of HCl into the optical path that 

also includes the native source gas. 

3.0 Definitions. (See PS-18 and Procedure 6 of appendix F to part 60 for the definitions used 

in this appendix.) 
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4.0 Interferences. Interferences are discussed in PS-18, section 4.0. 

5.0 Safety. The procedures required under this appendix may involve hazardous materials, 

operations and equipment. This procedure may not address all of the safety problems associated 

with these procedures. You as the facility or operator must establish appropriate safety and 

health practices and determine the applicable regulatory limitations prior to performing these 

procedures. As the CEMS user, you should consult instrument operation manuals, material safety 

data sheets, compressed gas safety requirements, and other Occupational Safety and Health 

Administration regulations for specific precautions to be taken. 

6.0 Equipment and Supplies. An example of equipment and supplies is described in section 6 

of PS-18. 

7.0 Reagents and Standards. SA materials must meet the requirements defined for reference 

gases in section 7 of PS-18 to perform this procedure with the following exception. You may 

use gases certified by the gas vendor to +5 percent to perform the daily calibration drift 

assessment in section 4.1 of Procedure 6 in appendix F of this part. 

Note: For extractive CEMS the concentrations of reference gases required for SA are likely to 

be significantly higher than the concentration of reference gases associated with PS-18 

requirements. 

8.0 Standard Addition and Dynamic Spiking Procedure. The standard addition procedure 

consists of measuring the native source gas concentration, addition of reference gas, and 

measurement of the resulting SA elevated source gas concentration. For extractive CEMS, HCl 

is spiked dynamically and thus, one must account for the dilution of sample gas from the 

addition of the HCl reference gas. For IP-CEMS, standard addition of an HCl reference gas is 

made by either adding an HCl reference gas to a flow through cell or inserting a sealed reference 
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gas cell into the measurement path of the CEMS. The enclosed cell or a fixed cell must contain 

an HCl concentration that accounts for the difference in path length of the cell used for SA 

relative to the measurement path. 

8.1 SA Concentration and Measurement Replicates. 

8.1.1 You must inject HCl gas to create a measured concentration based on the 

requirements of the particular performance test (e.g., LOD verification, CD, DSA). 

8.1.2 Each dynamic spike (DS) or standard addition (SA) replicate consists of a 

measurement of the source emissions concentration of HCl (native stack concentration) with and 

without the addition of HCl. With a single CEMS, you must alternate the measurement of the 

native and SA-elevated source gas so that each measurement of SA-elevated source gas is 

immediately preceded and followed by a measurement of native stack gas. Introduce the SA 

gases in such a manner that the entire CEMS is challenged. Alternatively, you may use an 

independent continuous HCl monitor to measure the native source concentration before and after 

each standard addition as described in section 8.1.4. 

8.1.3 Unless specified otherwise by an applicable rule, your SA-elevated 

concentration may not exceed 100 percent of span when the SA and native HCl concentration are 

combined. 

8.1.4 As an alternative to making background measurements pre- and post-SA, you 

may use an independent continuous HCl monitor as a temporary unit to measure native stack 

HCl concentration while simultaneously using the CEMS to measure the SA-elevated source 

concentration. If you use an independent continuous HCl monitor you must make one concurrent 

background or native HCl measurement using both the installed CEMS and the independent 

continuous HCl monitor, immediately before the SA procedure in section 8.2 or 8.3 begins, to 
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confirm that the independent monitoring system measures the same background concentration as 

the CEMS being qualified with this PS. 

8.2 SA Procedure for Extractive CEMS (Dynamic Spiking) 

8.2.1 Your HCl spike addition must not alter the total volumetric sample system flow 

rate or basic dilution ratio of your CEMS (if applicable). 

8.2.2 Your spike gas flow rate must not contribute more than 10 percent of the total 

volumetric flow rate through the CEMS. 

8.2.3 You must determine a dilution factor (DF) or relative concentration of HCl for 

each dynamic spike. Calibrated, NIST-traceable flow meters accurate to within 2.0 percent or 

highly accurate tracer gas measurements are required to make the necessary DF determinations 

at the accuracy required for this PS. Calibrated, NIST-traceable flow meters (e.g., venturi, 

orifice) accurate to within 2.0 percent should be recertified against an NIST-traceable flow meter 

annually. Note: Since the spiking mass balance calculation is directly dependent on the accuracy 

of the DF determination, the accuracy of measurements required to determine the total 

volumetric gas flow rate, spike gas flow rate, or tracer gas standard addition concentration is 

critical to your ability to accurately perform the DS procedure and calculate the results. 

8.2.4 You must monitor and record the total sampling system flow rate and sample 

dilution factor (DF) for the spiking and stack gas sampling systems to ensure they are known and 

do not change during the spiking procedure. Record all data on a data sheet similar to Table A1 

in section 13 of this appendix. 

8.2.4.1 You may either measure the spike gas flow and the total flow with calibrated 

flow meters capable of NIST traceable accuracy to  2.0 percent or calculate the flow using a 

stable tracer gas included in your spike gas standard. 
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8.2.4.2 If you use flow measurements to determine the spike dilution, then use 

Equation A1 in section 11.2.1 of this appendix to calculate the DF. Determination of the spike 

dilution requires measurement of HCl spike flow (Qspike) and total flow through the CEM 

sampling system (Qprobe). 

8.2.4.3 If your CEMS is capable of measuring an independent stable tracer gas, you 

may use a spike gas that includes the tracer to determine the DF using Equation A2 or A3 

(sections 11.2.2 and 11.2.3 of this appendix) depending on whether the tracer gas is also present 

in the native source emissions. 

8.2.4.4 For extractive CEMS, you must correct the background measurements of 

HCl for the dilution caused by the addition of the spike gas standard. For spiking systems that 

alternate between addition of HCl and zero gas at a constant DF, the background measurements 

between spikes will not be equal to the native source concentration. 

8.2.5 Begin by collecting unspiked sample measurements of HCl. You must use the 

average of two unspiked sample measurements as your pre-spike background. 

Note: Measurements should agree within 5.0 percent or three times the level of detection to 

avoid biasing the spike results. 

8.2.5.1 Introduce the HCl gas spike into the permanent CEMS probe, upstream of 

the particulate filter or sample conditioning system and as close to the sampling inlet as practical. 

8.2.5.2 Maintain the HCl gas spike for at least twice the DS response time of your 

CEMS or until the consecutive measurements agree within 5.0 percent. Collect two independent 

measurements of the native plus spiked HCl concentration. 
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8.2.5.3 Stop the flow of spike gas for at least twice the DS response time of your 

CEMS or until the consecutive measurements agree within 5.0 percent. Collect two independent 

measurements of the native HCl concentration. 

8.2.6 Repeat the collection of sample measurements in section 8.2.5 until you have 

data for each spike concentration including a final set of unspiked sample measurements 

according to section 8.2.5.3. 

8.2.7 Verify that the CEMS responded as expected for each spike gas injection, and 

that the data quality is not impacted by large shifts in the native source concentration. Discard 

and repeat any spike injections as necessary to generate a complete set of the required replicate 

spike measurements. 

8.2.8 Calculate the standard addition response (SAR) for extractive CEMS, using 

Equation A4 in section 11.2, of this appendix. 

8.2.9 If the DS results do not meet the specifications for the appropriate performance 

test in PS-18 or Procedure 6 of appendix F of this part, you must take corrective action and 

repeat the DS procedure. 

8.3 SA Procedure for IP-CEMS (Static Spiking). 

8.3.1 For IP-CEMS, you must make measurements of native source gas HCl 

concentration and an HCl standard addition using a calibration cell added to the optical 

measurement path. 

8.3.2 Introduce zero gas into a calibration cell located in the optical measurement 

path of the instrument. Continue to flush the zero gas into the cell for at least the SA response 

time of your CEMS or until two consecutive measurements taken are within 5.0 percent, then 
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collect two independent measurements. Alternatively you may measure native concentrations 

without the calibration cell in the optical path. 

8.3.3 Introduce the HCl spike gas into the calibration cell. Continue to flush the spike 

gas into the cell for at least the SA response time of your CEMS or until two consecutive 

measurements taken are within 5.0 percent of one another. Then collect two independent 

measurements of the SA addition to the native concentration. Alternatively you may insert a 

sealed calibration cell, containing HCl at the appropriate concentration, into the optical path to 

measure the SA addition to the native concentration. 

8.3.4 Repeat the collection of SA-elevated and native HCl measurements in sections 

8.3.2 and 8.3.3 until you have data for each SA concentration. Then, make a final native HCl 

measurement. The measured concentrations must be corrected for calibration cell and stack 

temperature, pressure and stack measurement path length. 

8.3.5 Calculate the standard addition response (SAR) for an IP-CEMS, using 

Equation A8 in section 11.3 of this appendix. 

8.3.6 If the SA results do not meet the specifications for the appropriate performance 

test in PS-18 or Procedure 6 of appendix F of this part, you must take corrective action and 

repeat the SA procedure. 

9.0 Quality Control. [Reserved] 

10.0 Calibration and Standardization. [Reserved] 

11.0 Calculations and Data Analysis. Calculate the SA response for each measurement and its 

associated native HCl measurement(s), using equations in this section. 

(Note: For cases where the emission standard is expressed in units of lb/MMBtu or corrected to 

a specified O2 or CO2 concentration, an absolute accuracy specification based on a span at stack 
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conditions may be calculated using the average concentration and applicable conversion factors. 

The appropriate procedures for use in cases where a percent removal standard is more restrictive 

than the emission standard are the same as in 40 CFR part 60, PS-2, sections 12 and 13.) 

11.1 Nomenclature 

Cspike = Actual HCl reference gas concentration spiked (e.g., bottle or reference gas 

concentration) ppmv; 

Ctracer spiked = Tracer gas concentration injected with spike gas (“reference concentration”) 

ppmv; 

DF = Spiked gas dilution factor; 

DSCD = Calibration drift determined using DS procedure (percent); 

DSE = Dynamic spike error (ppmv); 

ESA = Effective spike addition (ppmv); 

MCSA = Measured SA-elevated source gas concentration (ppmv); 

MCspiked = Measured HCl reference gas concentration i (ppmv); 

MCnative = Average measured concentration of the native HCl (ppmv); 

Mnative tracer = Measured tracer gas concentration present in native effluent gas (ppmv); 

Mspiked tracer = Measured diluted tracer gas concentration in a spiked sample (ppmv); 

Qspike = Flow rate of the dynamic spike gas (Lpm); 

Qprobe = Average total stack sample flow through the system (Lpm); 

S = Span (ppmv); 

SAR = Standard addition response (ppmv) 

11.2 Calculating Dynamic Spike Response and Error for Extractive CEMS. 
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11.2.1 If you determine your spike DF using spike gas and stack sample flow 

measurements, calculate the DF using equation A1: 

ܨܦ ൌ 	 ொೞ೛೔ೖ೐

ொ೛ೝ೚್೐

 Eq. A1 

11.2.2 If you determine your spike DF using an independent stable tracer gas that is not 

present in the native source emissions, calculate the DF for DS using equation A2: 

ܨܦ 	ൌ 	 ெೞ೛೔ೖ೐೏	೟ೝೌ೎೐ೝ

େ౪౨౗ౙ౛౨	౩౦౟ౡ౛ౚ

 Eq. A2 

11.2.3 If you determine your spike dilution factor using an independent stable tracer that 

is present in the native source emissions, calculate the dilution factor for dynamic spiking using 

equation A3: 

ܨܦ ൌ 	 ெೞ೛೔ೖ೐೏	೟ೝೌ೎೐ೝିெ೙ೌ೟೔ೡ೐	೟ೝೌ೎೐ೝ

஼೙ೌ೟೔ೡ೐	೟ೝೌ೎೐ೝିெ೙ೌ೟೔ೡ೐	೟ೝೌ೎೐ೝ

 Eq. A3 

11.2.4 Calculate the SA response using Equation A4: 

ܵܣܴ ൌ ܥܯ௦௣௜௞௘ௗ െ ሺ1 െ ܨܦሻ ∗ ܥܯ௔௡௧௜௩௘ Eq. A4 

11.2.5 Calculate the DS error using Equation A5. 

ܦܵܧ ൌ ܥܯ௦௣௜௞௘ௗ െ ܥܯ௔௡௧௜௩௘ െ ܨܦ ∗ ሺܥ௦௣௜௞௘ െ ܥܯ௔௡௧௜௩௘ሻ Eq. A5 

11.2.6 Calculating CD using DS. When using the DS option for determining mid-level 

CD, calculate the CD as a percent of span using equation A6: 

|ௌா 	 |஽ൌ ܦܥܵܦ

ௌ Eq. A6 

11.2.7 The effective spike addition (ESA) is the expected increase in the measured 

concentration as a result of injecting a spike. Calculate ESA using Equation A7: 

ܧܵܣ ൌ ܨܦ ∗ ሺܥ௦௣௜௞௘ െ ܥܯ௔௡௧௜௩௘ሻ Eq. A7 

11.3 Standard Addition Response for IP-CEMS. If you use an IP-CEMS and a 

calibration cell, calculate the SA response using Equation A8. 
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ܵܣܴ ൌ ܥܯௌ஺ െ ܥܯ௔௡௧௜௩௘ Eq. A8 

13. Tables and Figures. 

Table A1. Spike Data Sheet 

Facility name: Date: Time: 

Unit(s) tested: Test personnel: 

Analyzer make and model: 

Serial number: 

Calibration range: 

Qprobe 

(lpm) 

Qspike

(lpm) 

DF1 MCnative Actual Values DSE (ppmv) 

Pre Post Avg Cspike2

(ppmv) 

MCspiked3

(ppmv) 

 

 Average 

 SD 

1

 DF must be less than or equal to 10 percent for extractive CEMS. 

2

 Cspike = Actual HCl concentration of the spike gas, ppmv. 

3

 MCspiked = Measured HCl concentration of the spiked sample at the target level, ppmv. 

 
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3. Appendix F to part 60 is amended by adding “Procedure 6. Quality Assurance 

Requirements for Gaseous Hydrogen Chloride (HCl) Continuous Emission Monitoring Systems 

Used for Compliance Determination at Stationary Sources” to read as follows: 

Appendix F to Part 60 – Quality Assurance Procedures 

* * * * * 

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 (HCl) gas, CAS: 7647-01-0, continuous emission monitoring system (CEMS) 

that is used for determining compliance with emission standards for HCl 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 HCl 

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 
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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.) 

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; 
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(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 is being collected. 

4.1.5.1 Any time the average measured concentration of HCl exceeds 150 percent of 

the span value for greater than two hours, 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' HCl reference gas standard to the CEMS. Use `above span' 
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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 IPCEMS 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 fullscale 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 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: 

ൌ ݐ݈ݑݏ݁ݎ	ݏ݃ܽ	ܽܿ݇ݐݏ	݁݀ݖ݈݉ܽ݅ݎ݋ܰ

஼௘௥௧௜௙௜௘ௗ	௥௘௙௘௥௘௡௖௘	௚௔௦	௩௔௟௨௘

 .6-1Eq ݐ݈ݑݏ݁ݎ	ݏ݃ܽ	ܽܿ݇ݐݏ	݁݀ݎݑݏ݁ܽܯ	ݔ	 ௦௘	௢௙	௥௘௙௘௥௘௡௖௘	௚௔௨௔௟௩	ௗ௥௘௦௨௘௔ெ

4.2 Beam Intensity Requirement for HCl IP-CEMS. 
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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 
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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.

5.1 Temperature and Pressure Accuracy Assessment for IP CEMS. 

5.1.1 Stack or source gas temperature measurement audits for HCl IP-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 HCl 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 
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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 HCl 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 HCl 

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 values (or alternatively the emission standard) is used to assess the accuracy of the 
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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 HCl 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 HCl 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 
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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. You must calculate the dynamic 

spiking error (DSE) for each of the two upscale audit gases using the combination of Equation 

A5 and A6 in appendix A to PS-18 in appendix B to this part to determine CEMS accuracy. 

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 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 
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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 HCl 

concentration or in units of the emission standard. In cases where the RA is calculated on a 

concentration (ppmv) basis, if the average HCl concentration measured by the RM during the 

test is less than 75 percent of the HCl 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., outof-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 incontrol and if your source emits ≤ 75 percent of the HCl emission limit for each averaging period 

as specified in the relevant standard for eight consecutive quarters that include a minimum of 

two RATAs, 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). 
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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. 

ܴܣ ൌ ൣெேೌೡ೒ିோெೌೡ೒൧

ோெೌೡ೒

∗ 100 Eq. Eq. 6-2 

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 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. 

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∗ 100	 Eq. 6-3 

7.0 Reporting Requirements.
Page 88 of 89

This document is a prepublication version, signed by EPA Administrator, Gina McCarthy on 6/25/2015.  We have

taken steps to ensure the accuracy of this version, but it is not the official version.

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: 

 The RA for the RATA; 

 The accuracy for the CGA, RAA, or DSA; 

 Temperature and pressure sensor audit results for IP-CEMS; 

 The RM results, the reference gas certified values; 

 The CEMS responses; 

 The calculation results as defined in section 6; and 

 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. 
Page 89 of 89

This document is a prepublication version, signed by EPA Administrator, Gina McCarthy on 6/25/2015.  We have

taken steps to ensure the accuracy of this version, but it is not the official version.

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]