Quality Assurance Requirements for

Continuous Opacity Monitoring Systems at

Stationary Sources

Response to Comments
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Quality Assurance Requirements for

Continuous Opacity Monitoring Systems at

Stationary Sources

Response to Comments

Air Quality Assessment Division

Office of Air Quality Planning and Standards

U.S. Environmental Protection Agency

Research Triangle Park, NC 27711

March 2013
(This page intentionally left blank.)
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Table of Contents

LIST OF ACRONYMS AND ABBREVIATIONS iii

1.0 Introduction 1

1.1 Background 1

1.2 Commenters 1

1.3 Organization of this Document 1

2.0 Administrative Comments 3

2.1 Legal Authority for Rule 3

2.2 Procedure 3 vs. SIP Requirements 4

2.3 Procedure 3 vs. Part 63 Rules 4

2.4 Applicability 5

2.5 Compliance Deadline 6

2.6 Statutory and Executive Order Reviews 6

2.6.1 Paperwork Reduction Act 6

2.6.2 National Technology Transfer and Advancement Act 6

2.7 Terminology 7

2.7.1 Consistently Achieve Quality Assured Data 7

2.7.2 Out-of-Control Period 7

2.7.3 Noncompliance vs. Failure to Meet 8

2.7.4 Water Droplets 8

2.7.5 Daily Calibrations 8

2.7.6 Quarterly Calibrations 9

2.7.7 Annual Zero Alignment Audit 9

2.7.8 Zero-jig 10

2.8 ASTM Reference 11

3.0 Technical Comments 11

3.1 Status Indicator Checks 11

3.2 Units with Automatic Zero Compensation 11

3.3 Calibration Attenuators (Neutral Density Filters)–Recalibration Frequency 12

3.4 Quarterly Optical Alignment Checks 12

3.5 COMS Removal for Annual Zero Alignment 13

3.6 Quarterly Performance Audit Criteria – Misalignment Error 13

3.7 Data Capture Criteria 14

3.8 Corrective Action 14

3.9 30-Day Use of a Temporary Monitor 15

3.10 QA/QC Reporting Requirements/Data Assessment Reports (DARs) 15
ii

3.11 Diagnostic Tests After Repairs (Table 17-1) 16

4.0 Miscellaneous Comments 17

4.1 Alternative Compliance Option 17

4.2 Employee Safety 17

4.3 Equipment, Supplies, and Reagents 17

4.4 QC Program 18

4.5 Record Retention of QA/QC Procedures 18

4.6 Consequences of Failing QC Audits 19

4.7 Calibration and Standardization Procedures 19

4.8 Quarterly Calculation of 95 Percent Confidence Interval 20

4.9 Intervals to Record Data 20

4.10 External Audit Device 20

4.11 Clear Path Zero Value 20

4.12 Limitations on the Use of COMS Data 21

4.13 Data Retention 22

4.14 Daily Calibration Drift Check Calculation 22

4.15 Performance Specification 1 vs. Procedure 3 22
iii

List of Acronyms and Abbreviations

§ Section (used in this document for sections of the CFR)

Act Clean Air Act (42 U.S.C. 7401 – 7671q)

ASTM American Society for Testing and Materials

CAA Clean Air Act (42 U.S.C. 7401 – 7671q)

CD Calibration Drift

CEMS Continuous Emission Monitoring Systems

COMS Continuous Opacity Monitoring Systems

DAR Data Assessment Report

EPA U.S. Environmental Protection Agency

FR Federal Register

QA/QC Quality Assurance/Quality Control

PS-1 Performance Specification 1

SIP State Implementation Plan
1

1.0 Introduction

1.1 Background

On February 14, 2012, the U.S. Environmental Protection Agency (EPA or “we”) 

published a parallel proposed rule1 with a direct final rule2titled Quality Assurance 

Requirements for Continuous Opacity Monitoring Systems at Stationary Sources. We proposed 

to establish quality assurance and quality control (QA/QC) procedures (referred to as Procedure 

3) for continuous opacity monitoring systems (COMS) used to demonstrate continuous 

compliance with opacity standards in EPA issued or approved regulations.

This document presents EPA’s responses to public comments received on the proposed 

rule. All significant issues raised in timely public comments have been addressed.

1.2 Commenters

The public comment period initially ended on March 15, 2012 but was subsequently

extended to April 30, 2012 via notices

3

published in the Federal Register on March 8, 2012. 

Since we received adverse comments, we published a notice4to withdraw the direct final rule on 

March 28, 2012. We received comments from 27 commenters. This total counts each entity one 

time even if they submitted more than one comment letter. A list of the commenters and their 

affiliations is on page 2. 

1.3 Organization of this Document

After this introductory section, this document is divided into three sections as follows:

 Section 2 – Administrative Comments

 Section 3 – Technical Comments

 Section 4 – Miscellaneous Comments

 

1

The proposed rule was published on February 14, 2012 in the Federal Register, Volume 77, beginning on page 

8209 (77 FR 8209, February 14, 2012).

2

The direct final rule was published at 77 FR 8160, February 14, 2012.

3

The extension of the public comment period was announced at 77 FR 13977, March 8, 2012 for the direct final 

rule and at 77 FR 13997, March 8, 2012 for the parallel proposed rule.

4

The notice to withdraw the direct final rule was published at 77FR 18709, March 28, 2012.
2

Commenters on COMS Procedure 3

Proposed February 14, 2012

EPA-HQ-OAR-2010-0873

ID Commenter Affiliation

0003 Stephenie Moyer Nebraska Air Quality Division

0004 Donivan Porterfield ---

0006 Marsha Layman Quality Assurance Support Group, LLC

0009 Andy Seeber Wisconsin Department of Natural Resources

0010 Basil G. Constantelos Midwest Generation LLC & Homer City EME Generation

0011 Douglas B. Price Tesoro Companies, Inc.

0012 Monica Lopes NAES Corporation

0013 Lauren Freeman Utility Air Regulatory Group (UARG) – (pre-submittal - see 0029)

0014 Lisa Pongnon Calpine Corporation

0015 Anthony C. Sullivan Indianapolis Power & Light Co. (IPL)

0016 Cathe Kalisz American Petroleum Institute (API) – (pre-submittal – see 0036)

0017 Robert A. Hirsch Portland Cement Association (PCA) – (pre-submittal – see 0025)

0018 James S. Willis, III Titan America

0019 Ross May Searles Valley Minerals

0021 Jason Goodwin CARBO Ceramics, Inc.

0022 Bob Machaver ---

0023 Jim Peeler Emission Monitoring Inc. – (pre-submittal – see 0032)

0024 Jeffrey Poulton Energy Recovery Operations, Inc.

0025 Robert A. Hirsch Portland Cement Association (PCA)

0026 Christine Wyman Class of ‘85 Regulatory Response Group

0027 Robert Bessette Council of Industrial Boilers (CIBO)

0028 Mark Sedlacek Los Angeles Department of Water and Power (LADWP)

0029 Lauren Freeman Utility Air Regulatory Group (UARG) – w/ RMB comments attached

0030 Michael Bradley The Clean Energy Group

0031 Kevin Dempsey American Iron and Steel Institute (AISI)

0032 Jim Peeler Emission Monitoring, Inc.

0033 Randal Oswald Integrys Energy Group

0034 Gregory Wilkins Marathon Petroleum Company

0035 Lee Lemke Georgia Mining Association

0036 Cathe Kalisz American Petroleum Institute (API)

0037 Jay Hudson Santee Cooper
3

2.0 Administrative Comments

2.1 Legal Authority for Rule

Comment:

Four commenters (0025, 0029, 0034, and 0036) commented on our legal authority to 

impose the Procedure 3 QA/QC requirements. One of these commenters (0025) stated that we 

did not provide the CAA provision that allows us to impose the QA/QC requirements, and 

another one of the commenters (0029) requested that we identify the circumstances and legal 

authority for imposing the QA/QC requirements. 

Response:

Section 301(a) of the CAA authorizes the EPA Administrator to prescribe such 

regulations as are necessary to carry out his functions under the CAA and CAA section 114 

authorizes the EPA Administrator to require any person who owns or operates an emission 

source to, among other things, install, use, and maintain such monitoring equipment and use 

such audit procedures, or methods as may be necessary to determine whether the 

owner/operator is in violation of a standard of performance under CAA section 111. EPA has 

previously determined that the use of COMS is, in appropriate circumstances, necessary to 

ensure continuous compliance with opacity standards. EPA has now determined that the 

Procedure 3 QA/QC requirements are necessary to ensure that COMS used to demonstrate 

continuous compliance with opacity standards are properly maintained and operated.. Procedure 

3 applies to all COMS used to demonstrate continuous compliance with opacity standards 

specified in new source performance standards (NSPS) promulgated by EPA pursuant to section 

111(b) of the Clean Air Act, 42 U.S.C. §4211(b).

Comment:

The final two commenters (0034, 0036) stated that without amending individual subparts 

to reference Procedure 3, we don’t have the authority to impose Procedure 3 on any COMS 

except those used for continuous compliance under Part 60 and that were constructed or 

modified after Procedure 3 was proposed.

Response:

As stated above, we believe that we have the authority to impose COMS Procedure 3 

QA/QC requirements to ensure that COMS used to demonstrate continuous compliance with 

opacity standards are properly maintained and operated. We believe that this authority extends 

to requiring sources constructed, reconstructed or modified before COMS Procedure 3 was 

proposed to comply with the requirements to ensure that COMS used to demonstrate continuous 

compliance with opacity standards as required by a section 111(b) new source performance 

standards (NSPS) are properly maintained and operated. Part 60.13(a) of title 40 of the Code of 
4

Federal Regulations (CFR) specifically contemplates this We added a statement noting this 

authority in the paragraph titled “Background” in the preamble.

2.2 Procedure 3 vs. SIP Requirements

Comment:

Six commenters (0012, 0025, 0027, 0028, 0029, 0030) commented on Procedure 3 

requirements vs. SIP requirements. Commenter 0012 noted that Procedure 3 does not clarify if 

sources located in a state that has issued COMS QA guidance would be required to implement 

both state COMS QA guidance & Procedure 3. Another one of the commenters (0025) stated that 

source owners and operators should not have to comply with federal and state opacity monitoring 

and related QA requirements, and commenter 0027 stated that it is not clear as to whether a 

source will have to comply with state QA/QC procedures, EPA procedures, or both. Another one 

of the commenters (0028) stated that the applicability statement may not be specific enough to 

prevent sources subject to Title V Operating Permits or state regulations from being required to 

comply with Procedure 3. Commenter 0029 requested that we clarify that Procedure 3 would not 

apply to COMS required under a SIP unless the SIP specifically states that Procedure 3 applies. 

The final commenter (0030) stated that the Data Assessment Report (DAR) does not appear to be 

standardized and would not fit into what states require. The commenter recommended that for 

states with delegated air programs that source owners and operators not be required to submit 

duplicate DARs.

Response:

In the final regulatory text we clarified that COMS Procedure 3 is only required to be 

used when a COMS is used to demonstrate continuous compliance with an opacity

standard specified in a new source performance standard (NSPS) promulgated by EPA 

pursuant to section 111(d) if the Clean Air Act, 42 U.S.C. §7411(b). Source owners and 

operators must comply with both state and EPA requirements where both sets of 

requirements apply. A state can choose to adopt Procedure 3 in lieu of state-specific 

requirements or determine that compliance with Procedure 3 satisfies the state-specific 

requirements if it wishes to do so. In addition, a source subject to state-specific QA/QC 

procedures applicable to COMS can request in writing, pursuant to 40 CFR 60.13(i), that 

the Administrator approve the use of those procedures in lieu of COMS Procedure 3. If 

the Administrator does approve the use of the state-specific procedures, those procedures 

become the applicable requirements under the relevant NSPS. We also believe that the 

information required by Procedure 3 to be included in the DAR is necessary and

appropriate and is consistent with what most states require.

2.3 Procedure 3 vs. Part 63 Rules

Comment:

One commenter (0036) noted the potential for overlaps and conflicts between existing 

rules and Procedure 3.
5

Response:

As reflected in the revised applicability statement, Procedure 3 only applies to COMS 

used to demonstrate continuous compliance with opacity standards specified in new source 

performance standards (NSPS) promulgated by EPA pursuant to section 111(b) of the Clean Air 

Act, 42 U.S.C. §7411(b). As a result, the commenter’s examples of potential overlap with 

specific requirements in rules promulgated pursuant to section 112 of the Clean Air Act, 42 

U.S.C. §7412, are not relevant. Further, he commenter did not demonstrate that an actual 

conflict exists. Our intention is, nevertheless, to avoid duplicative and conflicting requirements, 

so if a source owner or operator determines that the requirements in Procedure 3 are actually in 

conflict with requirements in an existing rule, we will appreciate it if the owner or operator 

notifies us of this fact.

2.4 Applicability

Comment:

Seven commenters (0015, 0025, 0027, 0028, 0029, 0034, 0036) expressed concerns about 

the applicability statement. Three of the commenters (0015, 0025, 0027) requested that we define 

or clarify “federally enforceable regulations”.

Response:

We agree that the phrase “federally enforceable regulations” is ambiguous and clarified 

our intent by changing the language to “new source performance standards (NSPS) promulgated 

by EPA pursuant to section 111(b) of the Clean Air Act, 42 U.S.C. §7411(b)”. 

Comment:

Three of the commenters (0029, 0034, 0036) noted that Procedure 3 refers to 

Performance Specification 1 (PS-1), and stated that PS-1 applies only to COMS installed after 

February 6, 2001. One of the three commenters (0029) recommended that we develop separate 

requirements for pre-and post-February 6, 2001 COMS.

Response:

PS-1 was developed to address the initial installation of COMS, whereas Procedure 3 

addresses on-going QA/QC requirements. When we developed PS-1, we realized that some 

existing COMS were not being used for compliance purposes, and it was not our intent to require 

these source owners and operators to purchase new COMS. To accommodate these source 

owners and operators, we established the cutoff date of February 6, 2001. In other words, all new 

COMS installed after February 6, 2001 are required to meet PS-1 requirements.

Furthermore, Procedure 3 applies to all COMS (regardless of installation date) that are 

used to demonstrate continuous compliance with opacity standards in federally enforceable 

regulations as defined above. Procedure 3 does not prohibit source owners and operators from 

using COMS installed prior to February 6, 2001.

Comment:
6

The final commenter (0028) recommended that Procedure 3 allow different QA/QC 

requirements for sources depending on opacity limits. For example, sources subject to an opacity 

limit less than 10 percent could be required to perform QA/QC semi-annually, and sources 

subject to an opacity limit greater than 10 percent could be required to perform QA/QC annually.

Response:

We believe that the requirements in Procedure 3 are comprehensive and appropriate for

all COMS regardless of their opacity limit(s). Procedure 3 will result in national consistency in 

the application of QA/QC procedures by applicable sources using COMS.

2.5 Compliance Deadline 

Comment:

Fifteen commenters (0010, 0012, 0019, 0022, 0025, 0026, 0027, 0028, 0029, 0031, 0032, 

0033, 0034, 0036, 0037) urged us to increase the compliance deadline beyond 60 days after the 

date of publication of the rule. One commenter (0014) stated that for COMS installed and 

certified prior to the rule effective date, the rule should provide grandfathering such that the 

COMS would need to be removed no later than three years from the effective date of the rule and 

every three years thereafter. Most commenters requested that the compliance deadline be either 

four or six months after the rule publication date to allow sufficient time to develop QA/QC 

procedures, provide training, etc. 

Response:

We agree that 60 days from the date Procedure 3 is published in the Federal Register may

not allow adequate time for all sources to comply with the QA/QC requirements. Therefore, we 

extended the compliance deadline to 180 days from the date Procedure 3 is published.

2.6 Statutory and Executive Order Reviews

2.6.1 Paperwork Reduction Act

Comment:

Three commenters (0025, 0027, 0036) mentioned that Procedure 3 will result in 

implementation costs and budgetary impacts.

Response:

We believe that the requirements in applicable regulations are broad enough to include 

the information collection requirements specified in Procedure 3. In addition, the requirements in 

Procedure 3 are modeled after manufacturers’ maintenance recommendations. As a result, EPA 

believes that most, if not all, owners/operators are already following procedures similar to those 

specified in Procedure 3. Therefore, there are no additional costs, or reporting burden, associated

with implementing Procedure 3. 

2.6.2 National Technology Transfer and Advancement Act
7

Comment:

Two commenters (0004, 0031) commented on the National Technology Transfer and 

Advancement Act (NTTAA) language in the preamble of the Procedure 3 rule. The commenters 

noted that Procedure 3 involves technical standards.

Response:

Upon further review, the Agency agrees that Procedure 3 involves technical standards 

and revised the NTTAA language in the final rule.

2.7 Terminology

2.7.1 Consistently Achieve Quality Assured Data

Comment:

Six commenters (0011,0025, 0028, 0029, 0030, 0036) commented on the provision in 

§2.0(3) that allows owners and operators who consistently achieve quality assured data to request 

a semi-annual audit frequency by submitting the request in writing to the Administrator. Three of 

the commenters (0011, 0025, 0029) noted that the phrase “consistently achieves quality assured 

data” is vague and undefined, and the other three commenters (0028, 0030, 0036) requested that 

this provision be self-implementing or automatic (i.e., not require a petition to the 

Administrator).

Response:

We deleted the ambiguity in this provision, and specified in §2.0(2) that owners and 

operators who achieve quality assured data for four consecutive quarters may reduce their 

auditing frequency to semi-annually. If a performance audit is failed, the source must resume 

quarterly testing for that audit requirement until such time that it has again demonstrated 

successful performance over four consecutive quarters. In addition, we agreed to allow this 

provision to be self-implementing. In other words, we deleted the requirement to submit the 

request in writing to the Administrator. 

2.7.2 Out-of-Control Period

Comment:

One commenter (0028) requested that we redefine the out-of-control period to match the 

definition in Procedure 1 for gas CEMS. 

Response:
8

The commenter provided no basis for this request, and we believe that our proposed 

definition is appropriate for COMS. Therefore, we did not make any changes to the proposed 

definition.

2.7.3 Noncompliance vs. Failure to Meet

Comment:

One commenter (0029) requested that we change the term noncompliance to the phrases 

“fails to meet” and “failure to meet” for the out-of-control period for annual zero alignments and 

quarterly performance audits. The commenter noted that failure to meet a QA criterion indicates 

that the COMS data is not quality assured and does not indicate that a source is in a state of 

noncompliance.

Response:

We agree and replaced the term “noncompliance” with “fails to meet” and “failure to 

meet”.

2.7.4 Water Droplets

Comment:

Three commenters (0029, 0031, 0036) commented on §4.0 that discusses avoiding water 

droplet interferences. One of the commenters (0029) is concerned that the statement indicating 

that opacity compliance determinations cannot be made when water droplets are present is too 

narrow. The commenter noted that whether used for continuous compliance determinations or 

not, COMS are not accurate in the presence of water droplets. The other two commenters (0031, 

0036) noted that the proposed language could be interpreted to require a reheater.

Response:

To address the concerns of all three commenters and to be consistent with the language in 

PS-1, we replaced the term “water droplets” with “condensed water vapor” and added the 

statement “Therefore, COMS must be located where condensed water vapor is not present.”

2.7.5 Daily Calibrations

Comment:

Six commenters (0006, 0010, 0012, 0022, 0030, 0036) commented on the system checks 

required to be conducted daily. Three of the commenters (0006, 0010, 0030) requested that we 

define daily by specifying a minimum number of operating hours to qualify as a day, and one of 

the commenters (0036) requested that we clarify that daily means calendar days. Another one of 

the commenters (0012) requested that we consider allowing sources to discontinue daily
9

calibration checks for units that don’t operate for one week or more and require those sources to 

resume daily calibration checks the day before the unit is scheduled to resume operations. 

Response:

We re-defined daily to mean any portion of a calendar day that a unit operates and 

believe that by doing so, we have addressed the commenters’ concerns.

Comment:

The final commenter (0022) stated that daily calibrations should only be required on 

days that the unit is operating on a fuel subject to opacity monitoring. 

Response:

We believe this level of detail is inappropriate to include in Procedure 3.

2.7.6 Quarterly Calibrations

Comment:

Eight commenters (0006, 0012, 0022, 0026, 0029, 0030, 0033, 0036) requested that we 

define quarterly (i.e., include the minimum number of operating hours to qualify as an operating 

quarter), and five of the commenters (0006, 0012, 0026, 0029, 0033) recommended that we 

define quarter as one in which the unit operates at least 168 hours in a calendar quarter.

Response:

We agreed to clarify the term “quarterly” and defined it in the final rule as a calendar 

quarter in which a unit operates at least 168 hours.

2.7.7 Annual Zero Alignment Audit

Comment:

Six commenters (0012, 0021, 0026, 0028, 0030, 0036) commented on the annual zero 

alignment audit requirement. Two of the commenters (0030, 0036) mentioned that the term 

“annual” was unclear and requested that we define annual (e.g., specify minimum number of 

operating hours to qualify as a year), and one commenter (0012) inquired about whether the zero 

alignment audit should be performed annually or every 12 months. 

Response:

We added clarity by defining “annually” as a period wherein the unit is operating at least 

28 days in a calendar year.

Comment:
10

One commenter (0026) requested that the rule provide a grace period for completion of 

audits and stated that the annual zero alignment must be conducted while the unit is offline. 

Response:

However, the rule does not require that the annual zero alignment be conducted while the 

unit is offline.

Comment:

Another commenter (0021) stated that the annual zero alignment audit should not be 

required unless the COMS is replaced. 

Response:

We disagree. Based on input from COMS manufacturers, to ensure that the zero 

alignment is accurate, it is necessary to conduct this audit annually. 

Comment:

The final commenter (0028) requested that the zero alignment be conducted every three 

years instead of annually and stated that testing annually will require a substantial amount of 

manpower that may not significantly improve the value of the data. The commenter 

recommended that we allow incentives based on system performance criteria instead of imposing 

a mandatory annual requirement.

Response:

Section 10.3(2) allows owners and operators to use an external zero device to determine 

the zero alignment. In other words, source owners and operators are not required to remove the 

COMS annually if they use the external zero device alternative.

2.7.8 Zero-jig

Comment:

Two commenters (0026, 0033) commented on the term zero-jig in the annual zero 

alignment alternative in §10.3(2). Both commenters indicated that the use of the term zero-jig 

was unclear and inadequately defined. They also requested that we consult with COMS 

manufacturers to identify appropriate methods for conducting the annual zero alignment audit.

Response:

We agree with the commenters that the term zero-jig was not well-defined in the 

proposed rule and deleted the term from the final rule. The final rule uses the term external zero 
11

device only. We also discussed the annual zero alignment method with COMS manufacturers 

and confirmed that the method in the rule is appropriate.

2.8 ASTM Reference

Comment:

One commenter (0032) requested that Procedure 3 reference the most recent version of 

the ASTM D 6216 only. Another commenter (0029) noted that the proposed rule suggests that 

source owners and operators must comply with all three versions of the ASTM and suggested 

that we specify that source owners and operators may comply with the version in effect when the 

COMS was certified or, using their opinion, either of the two later versions. 

Response:

We believe that only the latest ASTM version should be referenced since the prior 

versions may contain obsolete information. Therefore, we referenced only the latest ASTM 

version (ASTM D6216-12) in the final rule.

3.0 Technical Comments

3.1 Status Indicator Checks

Comment:

Eight commenters (0006, 0010, 0022, 0027, 0029, 0034, 0036, 0037) noted that a fault 

status indicator does not necessarily mean that the data is invalid, and one commenter (0015) 

asked for clarification regarding whether corrective action, recordkeeping, and reporting are 

required when status indicator checks illuminate. 

We agree that a status indicator is a warning that opacity readings are nearing the limit 

and that the data is not necessarily invalid. Therefore, we deleted the statement in §10.1(3), “All 

COMS data recorded during periods in which the fault status indicators are illuminated are to be 

considered invalid.” You must continue to record data when the status indicator check 

illuminates. 

As stated in §10.1(3), you must take appropriate corrective action based on the 

manufacturer’s recommendations when the COMS is operating outside preset limits. Section 

10.5 requires you to have a corrective action program to address the repair and/or maintenance of 

your COMS. Although it is a good practice to keep records, recordkeeping and reporting are not 

required for daily status indicators.

3.2 Units with Automatic Zero Compensation

Comment:
12

One commenter (0014) asked that we clarify that §10.2(1) applies only to COMS with 

automatic zero compensation, and two commenters (0026, 0033) requested that we delete the 

requirement to record the value of the compensation applied to the effluent because some COMS 

are not equipped to record or display the zero compensation value. 

Response:

The language in §10.2(1) states “For units with automatic zero compensation...”. In 

other words, §10.2(1) only applies to COMS equipped with automatic zero compensation.

3.3 Calibration Attenuators (Neutral Density Filters)–Recalibration Frequency

Comment:

Five commenters (0021, 0027, 0029, 0034, 0036) commented on the recalibration 

frequency of calibration attenuators (or neutral density filters). Three of the commenters (0021, 

0027, 0029) stated that the requirement to inspect and calibrate neutral density filters (calibration 

attenuators) every six months is overly burdensome. The other two commenters (0034, 0036)

requested that Procedure 3 require calibration attenuators to be recalibrated annually in lieu of 

semi-annually. In addition, one of the commenters (0036) suggested that we replace the term 

“neutral density filters” with “calibration attenuators, either primary or secondary” to be 

consistent with language in Performance Specification 1.

Response:

We agree that inspecting and calibrating neutral density filters (attenuators) every six 

months is overly burdensome and revised the language in §10.2(2) to require source owners and 

operators to inspect and calibrate attenuators annually as opposed to every six months. In

addition, if two consecutive annual calibrations are within 0.5 percent opacity, the attenuators 

can be inspected and calibrated once every five years. We agree with the terminology suggestion 

and replaced the term “neutral density filters” with “calibration attenuators, either primary or 

secondary”.

3.4 Quarterly Optical Alignment Checks

Comment:

Five commenters (0026, 0027, 0028, 0030, 0033) noted that it is not feasible to check the 

optical alignment when the stack T is +/-50% of the typical operating T, and one commenter 

(0015) noted that §10.2(3) requires a unit to be online on a quarterly basis even if it would not be 

required otherwise. 

Response:
13

We agree and revised the language in §10.2(3) as follows. “You must check the optical 

alignment of the COMS in accordance with the instrument manufacturer’s recommendations. If 

the optical alignment varies with stack temperature, perform the optical alignment test when the 

unit is operating.”

3.5 COMS Removal for Annual Zero Alignment

Comment:

Nine commenters (0011, 0015, 0021, 0024, 0026, 0027, 0029, 0034, 0036) remarked that 

removing the COMS from the stack exposes the COMS to potential damage, presents a safety 

hazard, and is a monetary burden. Six of these commenters (0015, 0021, 0026, 0029, 0034, 

0036) requested that we delete the requirement to remove the COMS to conduct zero alignment 

audits, and one (0027) of the commenters suggested that the rule require the zero alignment audit 

when the boiler is down. 

Response:

The zero alignment test is necessary because the simulated zero device (an automated 

mechanism that produces a simulated clear path condition) is used daily to check the COMS's 

zero drift. If the simulated zero device is inaccurate, this will directly impact the instrument's 

daily zero drift readings. The accuracy of the simulated zero device is determined by comparing 

it to actual clear path conditions. The best way to establish this relationship between the 

simulated zero device and clear path conditions is by conducting the zero alignment test. The 

best way to ensure clear path conditions is by removing the COMS from it's monitoring location 

and setting it up at ground level. Based on input from COMS manufacturers, it was determined 

that the zero alignment test needs to be done off-stack annually unless you choose the alternative 

that allows the installation of an external zero device (which allows COMS removal from the 

stack every three years). In addition, based on our conversations with manufacturers, we believe 

that the risks for damage to occur when removing the COMS from the stack are minimal.

3.6 Quarterly Performance Audit Criteria – Misalignment Error

Comment:

Four commenters (0027, 0029, 0034, 0036) noted that the quarterly performance audit 

criterion in §10.4(3)(i) is problematic. The proposed rule states that the COMS is out-of-control 

if the results of a quarterly performance audit indicate noncompliance with the criterion that the 

optical alignment misalignment error exceeds 3 percent opacity. The commenters noted that 

there is no reliable methodology that relates the amount of misalignment with opacity, and one of 

the commenters (0029) suggested that we change the excessive inaccuracy criterion to adjust 

alignment relative to a specific reference mark or condition.

Response:
14

We agree with the commenters and changed the quarterly performance audit 

noncompliance criterion in §10.4(3)(i) to “the optical alignment indicator does not show proper 

alignment (i.e., does not fall within a specific reference mark or condition).”

3.7 Data Capture Criteria

Comment:

Nine commenters (0006, 0009, 0010, 0012, 0022, 0028, 0029, 0034, 0036) expressed 

concerns regarding the criterion for data capture and requested clarification regarding the 

definition of “operating hours” or that we delete the data capture criterion from Procedure 3 and 

address it in the applicable subpart.

Response:

We agree that data capture criterion should be addressed in the applicable subpart and 

revised §10.4(4) to reference the applicable subpart.

3.8 Corrective Action

Comment:

Six commenters (0006, 0010, 0014, 0025, 0029, 0036) commented on language in §10.5. 

Two commenters (0029, 0036) requested that we delete the specific corrective action 

requirements because they are too restrictive. 

Response:

We agree with these commenters and believe that it is appropriate to include corrective 

action maintenance and repair procedures in a guidance document. Therefore, we revised the 

language in §10.5 to reference a guidance document that discusses maintenance and repair 

procedures and diagnostic testing.

Comment:

Two of theses commenters (0006, 0010) requested that we allow the use of a 

probationary calibration test to conditionally validate data. Another one of these commenters

(0014) noted that there are five categories listed under §10.5, but the proposed rule mentioned

four classes of maintenance and repair procedures. The final commenter (0025) suggested that 

we consider changing §10.5 (Corrective Action) to §11.0 since §10.0 is entitled “What 

calibration and standardization procedures must I perform for my COMs?” 

Response:

Since we deleted the maintenance and repair categories and specific correction action 

maintenance and repair procedures, these comments are no longer applicable.
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3.9 30-Day Use of a Temporary Monitor

Comment:

Three commenters (0010, 0034, 0036) commented on the use of a temporary monitor in 

§10.6. Two of the commenters (0034, 0036) noted that §10.6 does not clearly define when a 

temporary COMS is collecting valid data.

Response:

We agree that we did not clearly define when a temporary COMS is collecting valid data. 

Therefore, we added a statement to §10.6 to indicate that data generated by the temporary COMS 

is considered valid when paragraphs (i) through (ix) of §10.6 (1) have been met.

Comment:

The other commenter (0010) stated that 30 days is not enough time to remove an existing 

monitor, ship it off-site for repairs, and return it to service. 

Response:

In the proposed rule, we based our decision to allow the use of a temporary monitor for 

30 days on discussions with COMS manufacturers. The manufacturers indicated that 30 days 

would be adequate time to troubleshoot, repair, and return COMS to owners and operators in 

most cases. However, to accommodate rare situations that may take longer, such as special 

orders, we have increased the timeframe for temporary monitor use from 30 days to 45 days.

3.10 QA/QC Reporting Requirements/Data Assessment Reports (DARS)

Comment:

Five commenters (0006, 0012, 0021, 0027, 0029) commented on the QA/QC reporting 

requirements referred to as Data Assessment Reports. One of the commenters (0006) asked for 

clarification regarding whether the reporting requirements in §10.9 includes daily status indicator 

checks, quarterly cumulative zero compensation checks, and annual primary zero alignment 

checks required in §10.0. Another commenter (0012) stated that it is unclear whether §10.9 

requires results of quarterly audits only or all daily zero and upscale drift checks performed 

during the quarter and the results of the quarterly audits to be included in the DAR.

Response:

The reporting requirements in §10.9 include daily status indicator checks, quarterly 

cumulative zero compensation checks, and annual primary zero alignment checks required in 

§10.0. To address both of these comments, we clarified the requirement by referencing §§10.1, 

10.2, and 10.3 in §10.9.
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Comment:

Two commenters (0021, 0027) noted that Procedure 3 refers to an example DAR in 

Procedure 1 but noted that the DAR in Procedure 1 is inconsistent with the requirements 

specified in §10.0 of Procedure 3. 

Response:

After reviewing §10.9, we realized that the DAR in Procedure 1 was not an appropriate 

example. The DAR in Procedure 1 addresses CEMS, whereas Procedure 3 deals with COMS. 

Therefore, we deleted the reference to the Procedure 1 DAR.

Comment:

One commenter (0029) noted that it is not appropriate to establish a reporting frequency

in a QA procedure and requested that we defer to the applicable regulation. 

Response:

We agree and deleted the reference to reporting results at the interval specified in this 

procedure. 

3.11 Diagnostic Tests After Repairs (Table 17-1)

Comment:

Five commenters (0011, 0022, 0029, 0034, 0036) provided comments regarding Table 

17-1 which included diagnostic tests after repairs. Four of these commenters (0011, 0029, 0034, 

0036) recommended that we delete the diagnostic test requirements (Table 17-1) from Procedure 

3, and three of these commenters (0011, 0029, 0036) further recommended that we specify

diagnostic test requirements in a guidance document. 

Response:

We decided to delete Table 17-1 because we realize that it is necessary to allow 

flexibility for repairs due to variations in COMS designs. Therefore, in lieu of the diagnostic 

tests required in Table 17-1, suggested diagnostic tests after repairs are given in a guidance 

document. 

Comment:

In addition, one of the commenters (0034) stated that Procedure 3 does not address how 

to handle COMS data collected during a diagnostic test event. 

Response:
17

Data collected during a diagnostic test event is considered invalid because the COMS is 

out-of-control during this time.

Comment:

One of the commenters (0022) suggested that in lieu of conducting a COMS 7-day

calibration drift (CD) check following certain maintenance activities that Procedure 3 should 

clarify that this audit check can be performed with the unit off-line. 

Response:

This comment no longer applies since we deleted Table 17-1.

4.0 Miscellaneous Comments

4.1 Alternative Compliance Option

Comment:

One commenter (0026) requested that we adopt an additional alternative compliance 

option that would allow sources to implement QA/QC requirements based on manufacturer and 

vendor recommendations in lieu of implementing Procedure 3. 

Response:

We believe that we allow the use of manufacturer’s recommendations where appropriate 

in Procedure3. Procedure 3 establishes the minimum QA/QC procedures for the entire QA/QC 

program.

4.2 Employee Safety

Comment:

One commenter (0025) stated that is is not appropriate to discuss employee safety in 

Procedure 3 and recommended that we delete the employee safety discussion in §5.0. 

Response:

However, we are not imposing safety regulations in Procedure 3. We are simply putting people 

on notice that there are safety concerns potentially associated with these QA/QC requirements. 

4.3 Equipment, Supplies, and Reagants

Comment:

One commenter (0029) requested that we delete the statements in §6.0 and §7.0 tying 

equipment and standards to PS-1 because the statements could be misread to require source 
18

owners and operators with COMS that were installed prior to 2001 to unnecessarily replace 

equipment that is still performing well. The commenter suggested that we indicate that §6.0 and 

§7.0 are reserved and stated that these sections are unnecessary since the relevant terms & 

equipment are defined elsewhere in the rule.

Response:

To clarify the Agency’s intent, we added the statement, “You are not required to purchase 

a new COMS if your existing COMS meets the requirements of Procedure 3” to §6.0 and §7.0.

4.4 QC Program

Comment:

Two commenters (0021, 0025) commented on the QC measures required in §9.0. One 

commenter (0021) stated that the requirement to develop a separate QC program is overly 

burdensome and redundant, and the other commenter (0025) requested that we change the 

requirement for the QC program to describe specific procedures to a recommendation to include 

the procedures. 

Response:

We believe that the QC measures in §9.0 are necessary and appropriate to ensure proper 

operation and maintenance of COMS. Your QC program may reference documents, such as, the 

manufacturer’s instructions for the COMS.

4.5 Record Retention of QA/QC Procedures

Comment:

One commenter (0029) noted that it is not appropriate to establish the record retention 

period in QA/QC procedures. The commenter also stated that we cannot require maintenance of 

records for more than three years without providing justification.

Response:

We agree with both of these comments and deleted the record retention period from §9.1. 

We retained the language in §10.11 that states that records must be kept for the period specified 

in the regulations requiring use of the COMS.

4.6 Consequences of Failing QC Audits

Comment:

Two commenters (0027, 0029) commented on the language in §9.2 regarding the 

consequences of failing QC audits. One commenter (0027) stated that it is not rational to 
19

mandate specific corrective actions and mentioned that the second audit failure may be caused by 

something totally unrelated to the first one. The other commenter (0029) stated that the 

requirement to revise QC procedures or repair or replace the COMS to correct deficiencies 

causing audit failures is unreasonable and beyond the scope of Procedure 3.

Response:

We revised the language in §9.2 as follows. “If you fail two consecutive annual audits, 

two consecutive quarterly audits, or five consecutive daily checks, you must either revise your 

QC procedures or determine if your COMS is malfunctioning. If you determine that your COMS 

is malfunctioning, you must then take the necessary correction action as specified in §10.5. If 

you determine that your COMS requires extensive repairs, you may use a substitute COMS 

provided the substitute meets the requirements in §10.6.”

4.7 Calibration and Standardization Procedures

Comment:

One commenter (0011) asked if the requirements of §10.0(1) to perform routine system 

checks would be met by performing daily calibrations and optical checks. The commenter also 

inquired about the difference between paragraphs 10.0(1) and 10.0(2).

Response:

The requirements of §10.0(1) to perform routine system checks would be met by

performing daily calibrations and optical checks. In response to the commenters’ second 

question, paragraph §10.0(1) discusses maintenance requirements that must occur more 

frequently than quarterly, such as, daily drift checks, and §10.0(2) discusses quarterly 

performance audit requirements.

Comment:

Two commenters (0029, 0032) stated that the 90 to 110 percent criterion for the 

simulated clear path condition in the annual zero alignment as specified in §10.0(3) should be 

changed to 90 to 190 percent as specified in ASTM D 6216. However, one commenter (0032) 

retracted their request to change this criterion upon realizing that the intended range in ASTM D 

6216 is 90 to 110 percent and noted that they plan to change the range to 90 to 110 percent in the 

ASTM D 6216-12.

Response:

In response, the most recent version of the ASTM D 6216 (ASTM D 6216-12) specifies 

the criterion as 90 to 110 percent, and Procedure 3 should be consistent with this language. 

Therefore, we did not change the proposed criterion in the final rule. In other words, the final 

rule specifies 90 to 110 percent as did the proposed rule.
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4.8 Quarterly Calculation of 95 Percent Confidence Interval

Comment:

One commenter (0021) stated that it is overly burdensome to calculate a 95% confidence 

interval quarterly as required in §10.2(2). The commenter stated that the 95% confidence interval 

provides limited information and requested that the quarterly frequency be reduced to annually. 

Response:

We disagree that this requirement is overly burdensome. Furthermore, the commenter did 

not provide a rationale to support reducing the requirement from quarterly to annually.

Therefore, this requirement remains the same as proposed.

4.9 Intervals to Record Data

Comment:

One commenter (0028) requested that we specify the interval for recording data and 

noted that they currently record data at six-minute intervals. 

Response:

We believe most COMS record data at six-minute intervals, and we are not suggesting 

that owners/operators change that recording interval. Furthermore, we do not believe that it is 

necessary to specify intervals for recording data. 

4.10 External Audit Device

Comment:

One commenter (0022) requested that we clarify the requirement in §10.2(2) to confirm 

that the external audit device produces a zero value within one percent opacity. 

Response:

We agreed to clarify this language and re-worded the requirement in §10.2(2) to state 

“When the external audit device is installed, with no calibration filter inserted, the COMS 

measurement reading must be less than or equal to one percent opacity.”

4.11 Clear Path Zero Value

Comment:

Three commenters (0027, 0032, 0036) commented on the clear path zero value. One 

commenter (0032) requested that we delete the allowance to perform the primary clear path 
21

calibration for the COMS as installed if the process is not operating and the monitor path is free 

of particulate matter since this allowance conflicts with ASTM D 6216-07. 

Response:

We agree and deleted this allowance from §10.3(1). Therefore, allowing the COMS to be 

removed every three years is no longer permissible using the primary zero alignment method; for 

this method, the COMS must be removed annually. As a result of deleting this allowance, it was 

necessary to change “COMS may be removed” in the second sentence of §10.3(1) to “COMS 

must be removed”. Also, as a result of deleting the allowance in §10.3(1), it was necessary to 

delete §10.3(4) because the proposed language in §10.3(4) implied that the COMS would have to 

remain on the stack.

Comment:

Another commenter (0036) stated that the clear path zero determination should be based 

on an average value or some other statistically-derived value they believe is more representative 

and defensible in lieu of the minimum observed value. The commenter suggested that the zero 

value be based on the 5th percentile lowest value.

Response:

However, we deleted the option to perform the zero alignment test with the COMS on 

stack, with the monitor path free of particulate matter from §10.3(1). Therefore, this comment is 

no longer applicable.

Comment:

The final commenter (0027) noted that §10.3(1) allows an adjustment of the clear path 

zero as long as the two-hour readings don’t vary more than 3% opacity, whereas §10.4(2) defines 

the COMS as out of control if the zero alignment exceeds 2% opacity. The commenter believes 

that clear stack zero alignment should be acceptable if readings vary by less than 3% opacity.

Response:

Since we deleted reference to 3% opacity in §10.3(1), this comment is no longer 

applicable.

4.12 Limitations on the Use of COMS Data

Comment:

One commenter (0025) requested that we delete §10.8 which addresses limitations on the 

use of COMS data collected during out-of-control periods. 

Response:
22

We disagree. We believe that it is appropriate to address limitations on the use of COMS 

data in Procedure 3. We have consistently addressed these limitations in other QA/QC 

procedures (i.e., Procedures 1 and 2). 

4.13 Data Retention

Comment:

One commenter (0025) noted that §10.11 of Procedure 3 states that QA data must be 

maintained for the period in the applicable regulation, whereas §10.6(9) references permanently 

maintained records.

Response:

We agree that the language in §10.6(9) could be interpreted to imply that records for 

temporary monitors are to be kept on a permanent basis which was not our intent. Therefore, we 

have deleted the phrase “or in other appropriate permanently maintained records” from §10.6(9). 

All records generated as a result of meeting Procedure 3 requirements must be kept for the period 

specified in the applicable regulation as stated in §10.11.

4.14 Daily Calibration Drift Check Calculation

Comment:

One commenter (0012) stated that the daily calibration drift (CD) check calculations are 

not in §12.0 of PS-1 as stated in the proposed rule. 

Response:

We added the word “quarterly” to the question in §12.0 to make it clear that the 

calculations referred to in §12.0 are for quarterly performance audits.

4.15 PS-1 vs. Procedure 3

Comment:

One commenter (0028) recommended that we revise PS-1 prior to issuing the final 

Procedure 3 requirements.

Response:

We don’t believe that it is necessary to revise PS-1 prior to publishing the final Procedure 

3 because PS-1 deals with the initial installation of a COMS; Procedure 3 deals with the ongoing operation of a COMS and ensures the instrument continues to produce quality data. 

Revisions to PS-1 will have little to no impact on Procedure 3.