Federal Register / Vol. 89, No. 42 / Friday, March 1, 2024 / Proposed Rules 15101 

and low-income populations to the 

greatest extent practicable and 

permitted by law. EPA defines 

environmental justice (EJ) as ‘‘the fair 

treatment and meaningful involvement 

of all people regardless of race, color, 

national origin, or income with respect 

to the development, implementation, 

and enforcement of environmental laws, 

regulations, and policies.’’ EPA further 

defines the term fair treatment to mean 

that ‘‘no group of people should bear a 

disproportionate burden of 

environmental harms and risks, 

including those resulting from the 

negative environmental consequences of 

industrial, governmental, and 

commercial operations or programs and 

policies.’’ 

TDEC did not evaluate EJ 

considerations as part of its SIP 

submittal; the CAA and applicable 

implementing regulations neither 

prohibit nor require such an evaluation. 

EPA did not perform an EJ analysis and 

did not consider EJ in this proposed 

action. Due to the nature of the action 

being proposed here, this proposed 

action is expected to have a neutral to 

positive impact on the air quality of the 

affected area. Consideration of EJ is not 

required as part of this proposed action, 

and there is no information in the 

record inconsistent with the stated goal 

of E.O. 12898 of achieving EJ for people 

of color, low-income populations, and 

Indigenous peoples. 

List of Subjects in 40 CFR Part 52 

Environmental protection, Air 

pollution control, Incorporation 

byreference, Intergovernmental 

relations, Particulate matter, Reporting 

and recordkeeping requirements. 

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

Dated: February 26, 2024. 

Jeaneanne Gettle, 

Acting Regional Administrator, Region 4. 

[FR Doc. 2024–04362 Filed 2–29–24; 8:45 am] 

BILLING CODE 6560–50–P 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 63 

[EPA–HQ–OAR–2022–0491; FRL–9992–01– 

OAR] 

RIN 2060–AV81 

EPA Method 320—Measurement of 

Vapor Phase Organic and Inorganic 

Emissions by Extractive Fourier 

Transform Infrared (FTIR) 

Spectroscopy 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Proposed rule. 

SUMMARY: This action proposes editorial 

and technical revisions to the 

Environmental Protection Agency’s 

(EPA’s) Method 320 (Measurement of 

Vapor Phase Organic and Inorganic 

Emissions by Extractive Fourier 

Transform Infrared (FTIR) 

Spectroscopy). The proposed revisions 

include updating the validation and 

quality assurance (QA) spiking 

procedures of the method to provide a 

more performance-based approach with 

specified acceptance criteria. The 

proposed revisions will provide 

flexibility to the stack testing 

community while ensuring consistent 

implementation and quality of the 

measurement results across emissions 

sources and facilities. 

DATES: Comments. Comments must be 

received on or before April 30, 2024. 

Public Hearing. The EPA will hold a 

virtual public hearing on March 29, 

2024 if a request for a virtual public 

hearing is received on or before March 

8, 2024. Refer to the SUPPLEMENTARY

INFORMATION section for additional 

information on the virtual public 

hearing. 

ADDRESSES: You may submit comments, 

identified by Docket ID No. EPA–HQ– 

OAR–2022–0491, by any of the 

following methods: 

• Federal eRulemaking Portal: 

https://www.regulations.gov/ (our 

preferred method). Follow the online 

instructions for submitting comments. 

• Email: a-and-r-docket@epa.gov. 

Include Docket ID No. EPA–HQ–OAR– 

2022–0491 in the subject line of the 

message. 

• Fax: (202) 566–9744. Attention 

Docket ID No. EPA–HQ–OAR–2022– 

0491. 

• Mail: U.S. Environmental 

Protection Agency, EPA Docket Center, 

Docket ID No. EPA–HQ–OAR–2022– 

0491, Mail Code 28221T, 1200 

Pennsylvania Avenue NW, Washington, 

DC 20460. 

• Hand/Courier Delivery: EPA Docket 

Center, WJC West Building, Room 3334, 

1301 Constitution Avenue NW, 

Washington, DC 20004. The Docket 

Center’s hours of operation are 8:30 

a.m.—4:30 p.m., Monday—Friday 

(except Federal Holidays). 

Instructions: All submissions received 

must include the Docket ID No. for this 

rulemaking. Comments received may be 

posted without change to https://

www.regulations.gov/, including any 

personal information provided. For 

detailed instructions on sending 

comments and additional information 

on the rulemaking process, see the 

‘‘Public Participation’’ heading of the 

SUPPLEMENTARY INFORMATION section of 

this document. 

FOR FURTHER INFORMATION CONTACT: Dr. 

David Nash, Office of Air Quality 

Planning and Standards, Air Quality 

Assessment Division (E143–02), 

Environmental Protection Agency, 

Research Triangle Park, NC 27711; 

telephone number: (919) 541–9425; fax 

number: (919) 541–0516; email address: 

nash.dave@epa.gov. 

SUPPLEMENTARY INFORMATION: 

Preamble acronyms and 

abbreviations. Throughout this 

document, the use of ‘‘we,’’ ‘‘us,’’ or 

‘‘our’’ is intended to refer to the EPA. 

We use multiple acronyms and terms in 

this preamble. While this list may not be 

exhaustive, to ease the reading of this 

preamble and for reference purposes, 

the EPA defines the following terms and 

acronyms here: 

ASTM American Society for Testing and 

Materials 

CAA Clean Air Act 

CBI Confidential Business Information 

CFR Code of Federal Regulations 

CTS calibration transfer standard 

EPA Environmental Protection Agency 

FTIR Fourier Transform Infrared 

FTP File Transfer Protocol 

IR infrared 

NAICS North American Industry 

Classification System 

NESHAP National Emissions Standards for 

Hazardous Air Pollutants 

NIST National Institute of Standards and 

Technology 

NSPS New Source Performance Standards 

NTTAA National Technology Transfer and 

Advancement Act 

OAQPS Office of Air Quality Planning and 

Standards OMB Office of Management and 

Budget 

PRA Paperwork Reduction Act 

PTFE polytetrafluoroethane 

QA quality assurance 

RFA Regulatory Flexibility Act 

SF6 sulfur hexafluoride 

TTN Technology Transfer Network 

UMRA Unfunded Mandates Reform Act 

VCS Voluntary Consensus Standard 

WJC William Jefferson Clinton 

mm micron 

Organization of this document. 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? 

II. Public Participation 

A. Written Comments 

B. Participation in Virtual Public Hearing 

III. Background 

IV. Summary of Proposed Revisions to 

Method 320 

A. Section 1.0 (Introduction) 

B. Section 2.0 (Summary of Method) 

C. Section 3.0 (Definitions) 

D. Section 4.0 (Interferences) 


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E. Section 5.0 (Safety)

F. Section 6.0 (Equipment and Supplies)

G. Section 7.0 (Reagents and Standards)

H. Section 8.0 (Sampling and Analysis

Procedure)

I. Section 9.0 (Quality Control)

J. Section 10.0 (Calibration and

Standardization)

K. Section 11.0 (Data Analysis and

Calculations) 

L. Section 12.0 (Method Performance Data

Analysis and Calculations)

M. Section 13.0 (Method Validation

Procedure)

N. Section 14.0 (Pollution Prevention)

O. Section 15.0 (Waste Management)

P. Section 16.0 (References)

Q. New Section 17.0 (Tables, Diagrams,

Flowcharts, and Validation Data)

R. Addendum To Test Method 320

IV. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory

Planning and Review and Executive

Order 14094: Modernizing 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 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 and Executive Order 14096:

Revitalizing Our Nation’s Commitment 

to Environmental Justice for All 

I. General Information

A. Does this action apply to me?

The proposed amendments to Method

320 apply to industries that are subject 

to certain provisions of 40 CFR parts 60 

and 63. The source categories and 

entities potentially affected are listed in 

table 1 of this preamble. This table is 

not intended to be exhaustive, but rather 

provides a guide for readers regarding 

entities likely to be regulated by this 

action. This table lists the types of 

entities that EPA is now aware could 

potentially be affected by this action. 

Other types of entities not listed in the 

table could also be regulated. 

TABLE 1—POTENTIALLY AFFECTED SOURCE CATEGORIES

Category NAICSa Examples of regulated entities 

Industry ............................................ 321211 ........................................... Plywood and Composite Wood Products. 

324110 ........................................... Petroleum Refineries. 

325211 ........................................... Polyvinyl Chloride and Copolymers Production. 

327410 ........................................... Lime Manufacturing Plants. 

333242 ........................................... Semiconductor Manufacturing. 

562211 ........................................... Hazardous Waste Combustors. 

327993 ........................................... Mineral Wool Production. 

322120 ........................................... Kraft Pulp and Paper Mills. 

2211, 48621, 92811, 211111, 

211112, and 622110.

Stationary Reciprocating Internal Combustion Engines. 

a North American Industry Classification System (2022). 

If you have any questions regarding 

the applicability of the proposed 

changes to Method 320, contact the 

person listed in the preceding FOR

FURTHER INFORMATION CONTACT section. 

B. Where can I get a copy of this

document and other related

information?

The docket number for this action is 

Docket ID No. EPA–HQ–OAR–2022– 

0491. In addition to being available in 

the docket, an electronic copy of the 

proposed method revisions is available 

on the Technology Transfer Network 

(TTN) website at https://www3.epa.gov/ 

ttn/emc/methods/. The TTN provides 

information and technology exchange in 

various areas of air pollution control. 

II. Public Participation

A. Written Comments

Submit your comments, identified by

Docket ID No. EPA–HQ–OAR–2022– 

0491, at https://www.regulations.gov 

(our preferred method), or the other 

methods identified in the ADDRESSES

section. Once submitted, comments 

cannot be edited or removed from the 

docket. The EPA may publish any 

comment received to its public docket. 

Do not submit to EPA’s docket at 

https://www.regulations.gov any 

information you consider to be 

Confidential Business Information (CBI), 

Proprietary Business Information (PBI), 

or other information whose disclosure is 

restricted by statute. Multimedia 

submissions (audio, video, etc.) must be 

accompanied by a written comment. 

The written comment is considered the 

official comment and should include 

discussion of all points you wish to 

make. The EPA will generally not 

consider comments or comment 

contents located outside of the primary 

submission (i.e., on the web, cloud, or 

other file sharing system). Please visit 

https://www.epa.gov/dockets/ 

commenting-epa-dockets for additional 

submission methods; the full EPA 

public comment policy; information 

about CBI, PBI, or multimedia 

submissions; and general guidance on 

making effective comments. 

B. Participation in Virtual Public

Hearing

If a request for a virtual public hearing 

is received on or before March 8, 2024 

the EPA will hold a virtual public 

hearing on March 29, 2024. To request 

a virtual public hearing or to register to 

speak at the virtual hearing, please 

contact Mr. David Nash at (919) 541– 

9425 or nash.dave@epa.gov. The last 

day to pre-register to speak at the 

hearing will be March 22, 2024. On 

March 26, 2024, the EPA will post a 

general agenda for the hearing that will 

list pre-registered speakers in 

approximate order at: https://

www3.epa.gov/ttn/emc/methods. 

The EPA encourages commenters to 

provide the EPA with a copy of their 

oral testimony electronically by 

emailing it to Mr. David Nash at nash.

dave@epa.gov. The EPA also 

recommends submitting the text of your 

oral comments as written comments to 

the rulemaking docket. 

The EPA may ask clarifying questions 

during the oral presentations but will 

not respond to the presentations at that 

time. Written statements and supporting 

information submitted during the 

comment period will be considered 

with the same weight as oral comments 

and supporting information presented at 

the public hearing. 

Please note that any updates made to 

any aspect of the hearing are posted 

online at https://www3.epa.gov/ttn/ 


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emc/methods. The EPA does not intend 

to publish a document in the Federal 

Register announcing updates. 

III. Background 

Method 320 describes the procedures 

for the measurement of vapor phase 

organic and inorganic emissions by 

Fourier Transform Infrared (FTIR) 

spectroscopy. The EPA promulgated 

Method 320 along with the National 

Emissions Standards for Hazardous Air 

Pollutants (NESHAP) for Portland 

Cement Manufacturing Industry (40 CFR 

part 63, subpart LLL) on June 14, 1999 

(64 FR 31898) under section 112 of the 

Clean Air Act (CAA) as amended. Since 

promulgation, the EPA has incorporated 

the use of Method 320 for demonstrating 

compliance with emissions standards 

into numerous NESHAP and New 

Source Performance Standards (NSPS). 

Over the 24-year period since 

promulgation, the use of FTIR 

spectroscopy has evolved as testing 

contractors, analytical laboratories, the 

EPA, and State entities have developed 

new standard operating procedures and 

methods to reflect improvements in 

sampling and analytical techniques. In 

2017, the EPA held a series of informal 

discussions with stakeholders in the 

measurement community to identify 

technical issues related to measuring 

emissions using FTIR spectroscopy and 

potential revisions to Method 320. The 

stakeholders consisted of a cross-section 

of interested parties including 

representatives from State regulatory 

entities, various EPA offices, analytical 

laboratories, emission testing firms, 

analytical standards vendors, 

instrument vendors, and others with 

experience in FTIR spectroscopy and 

Method 320. The docket for this action 

contains summaries of the stakeholder 

discussions. 

IV. Summary of Proposed Revisions to 

Method 320 

In this action, the EPA proposes 

technical revisions that update the 

validation and quality assurance (QA) 

spiking procedures of Method 320 to 

provide a more performance-based 

approach. The proposed revisions 

would more closely align Method 320 

with the EPA’s approach to emissions 

measurement, which emphasizes 

specifying performance-based criteria in 

test methods. Instead of specifying 

exactly how stack testers should use or 

perform a particular method procedure, 

the method defines the criteria that 

must be met for a specific method 

element, which provides stack testers 

with flexibility while maintaining the 

quality and reliability of the 

measurement results. The EPA is also 

proposing technical revisions and 

editorial changes to clarify and update 

the requirements and procedures 

specified in Method 320, including 

removing the batch sampling 

procedures. 

A. Section 1.0 (Introduction) 

In this action, the EPA proposes to 

revise the name of section 1.0 from 

‘‘Introduction’’ to ‘‘Scope and 

Application,’’ to update the 

introductory paragraph to remove 

references to the FTIR Protocol, and to 

remove the note regarding use of sample 

conditioning systems. The EPA also 

proposes to renumber and update 

sections 1.1.1 (Analytes) and 1.1.2 

(Applicability) to sections 1.1 and 1.2, 

respectively, and to replace the existing 

sections 1.2 (Method Range and 

Sensitivity), 1.3 (Sensitivity), and 1.4 

(Data Quality) with a revised section 1.3 

(Data Quality Objectives). 

B. Section 2.0 (Summary of Method) 

In this action, the EPA proposes to 

update section 2.0 by revising sections 

2.1 (Principle) and 2.2 (untitled) and 

removing sections 2.3 (Reference 

Spectra Availability) and 2.4 (Operator 

Requirements). In section 2.1, the EPA 

proposes to remove the title and 

consolidate sections 2.1.1 through 2.1.5 

and the introductory paragraph to 

section 2.2 (Sampling and Analysis) into 

a single paragraph. In section 2.2, the 

EPA also proposes to remove the 

discussion of Beer’s Law in section 2.2.1 

and to update the references to method 

evaluation and validation and pre-test 

procedures. 

C. Section 3.0 (Definitions) 

In this action, the EPA proposes to 

remove the following definitions for 

technical terms that are not needed in 

the proposed Method 320 and for terms 

commonly used in the emissions 

measurement community for which a 

definition is unnecessary: 

• Batch Sampling. 

• Concentration. 

• Continuous Sampling. 

• Emissions Test. 

• Gas Cell. 

• Independent Sample. 

• Interferant. 

• Measurement. 

• One Hundred Percent Line. 

• Quantitation Limit. 

• Reference Calibration Transfer 

Standard (CTS). 

• Root Mean Square Difference. 

• Sample Analysis. 

• Sampling Resolution. 

• Sampling System. 

• Screening. 

• Sensitivity. 

• Standard Spectrum. 

• Surrogate. 

• Test CTS. 

• Truncation. 

• Zero Filling. 

• Validation. 

• Validation Run. 

The EPA also proposes revisions to 

five definitions currently used in 

Method 320. Table 2 of this preamble 

presents the proposed revisions for each 

definition. 

TABLE 2—PROPOSED REVISIONS TO EXISTING DEFINITIONS

Term Revision Proposed definition 

Analyte ................................. Clarify that Method 320 can measure more than one 

analyte per test.

Analyte means a compound that the method is intended to measure. This method is a multi-component method; therefore, several analytes may be targeted for a given test. 

Background Deviation .......... Move the performance criteria from the definition to revised section 13.2 (Background Deviation).Background deviation means a deviation from 100% 

transmittance in any region of the 100% line. 

CTS [Calibration Transfer 

Standard] Standard.

Update the definition to remove the redundant ‘‘standard’’ in the term and to specify the acceptable CTS 

gases.

Calibration transfer standard (CTS) means a certified 

gas calibration standard used to verify instrument 

stability. For the purposes of this method, the CTS 

must be ethylene, methane, or carbon dioxide. Other 

compounds may be used only with the Administrator’s approval. 


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TABLE 2—PROPOSED REVISIONS TO EXISTING DEFINITIONS—Continued 

Term Revision Proposed definition 

Reference Spectrum ............ Change the term to plural (i.e., ‘‘Reference Spectra’’), 

clarify the definition, and remove the reference to the 

FTIR Protocol.

Reference spectra means a spectra of a pure sample 

gas obtained at a known concentration under controlled conditions of pressure, temperature, and 

pathlength. 

Run ....................................... Replace ‘‘measurements’’ with ‘‘samples’’ and remove 

the minimum requirement specifications.

Run means a series of samples taken successively 

from the stack or duct. A test normally consists of a 

specific number of runs. 

The EPA also proposes to add 

definitions for the key technical terms 

shown in table 3 of this preamble to 

improve the clarity of the principles and 

procedures used in Method 320. 

TABLE 3—PROPOSED NEW DEFINITIONS

Term Proposed definition 

Absorbance .......................... The negative logarithm of transmission represented by the relationship A = ¥log(I/I0), where I is the transmitted 

intensity of light, and I0 is the incident intensity of light upon a molecule. 

Absorptivity ........................... The amount of infrared radiation absorbed by each molecule. 

Analyte Spiking .................... The process of quantitatively adding calibration standards to source effluent. Analyte spiking is used to evaluate 

the ability of the sample transport and FTIR measurement systems to quantify the target analyte(s). 

Analytical Algorithm .............. The method used to quantify the concentration of both target analyte(s) and additional compounds in a sample 

matrix that may introduce analytical interferences in each FTIR spectrum. 

Analytical Interference .......... A spectral feature that complicates, and may even prevent, the analysis of an analyte. Analytical interferences 

can be background or spectral interferences. Background interferences result from a change in light throughput 

relative to the single beam background. This can be due to factors such as deposits on reflective surfaces and 

windows, temperature changes, a change in detector sensitivity, a change in infrared source output, or instrument electronics failure. Spectral interferences arise due to the presence of interfering compounds that have 

overlapping absorption features with the analytes of interest. 

Apodization ........................... A mathematical transformation that is used to adjust the instrument line shape for measured peaks. There are 

various types of apodization functions; the most common are boxcar, triangular, Happ-Genzel, and Beer-Norton 

functions. 

Background Spectrum .......... A spectrum taken in the absence of absorbing species or sample gas matrix, typically conducted using nitrogen 

or zero air. 

Bandwidth ............................. The width of a spectral feature. This width is commonly listed as the full width at half the maximum of the spectral feature. 

Beam Splitter ........................ A device located in the interferometer that divides the incoming infrared radiation into two separate beams that 

travel two separate paths before recombination. 

Classical Least Squares ...... A method of analyzing multicomponent spectra by scaling reference absorbance spectra to unknown measured 

spectra. 

Double Beam Spectrum ....... A transmission or absorbance spectrum derived by dividing the sample single beam spectrum by the background 

spectrum. 

Fourier Transform ................ A mathematical transform that allows the conversion of the detector response as a function of time to intensity as 

a function of frequency. 

Fundamental CTS ................ An NIST-traceable CTS reference spectrum with known temperature and pressure that has been obtained using 

an absorption cell with an accurately known optical pathlength. 

Interferogram ........................ A pattern that contains the effects of the wave interference that are produced from an interferometer. 

Interferometer ....................... A device used to produce interference spectra, by dividing a beam of radiant energy into two or more paths. One 

path strikes a fixed mirror and the second path strikes a moving mirror generating an optical path difference 

that varies over time between them. The recombined beams produce constructive and destructive interference 

as a function of changing pathlength. The Michelson interferometer, used in FTIR instruments, performs this 

function. 

Partial Least Squares ........... A method for analyzing multicomponent spectra by combining features from principal component and multiple regression analysis. It has been found to be most useful when predicting a set of dependent variables from a 

large set of independent variables. 

Resolution ............................ The minimum separation that two spectral features must have to distinguish one feature from the another. 

Retardation ........................... The optical path difference between two beams in an interferometer. 

Single Beam Spectrum ........ The Fourier transformed interferogram representing detector response versus wavenumber. 

Test ...................................... The series of runs required by the applicable regulation. 

Tracer Gas ........................... A stable, non-reactive species that is easily transportable and can be blended in a gas cylinder with a target 

analyte to confirm the dilution ratio of a dynamic spike. 

Transmittance ....................... The amount of infrared radiation that is not absorbed by the sample. Percent transmittance is represented by the 

following equation: %T = (I/I0) × 100. 

D. Section 4.0 (Interferences) 

In section 4.0 (Interferences), the EPA 

proposes to consolidate sections 4.1 

(Analytical Interferences) and 4.2 

(Sampling System Interferences) into 

revised section 4.0 and to incorporate 

the discussion of background and 

spectral interferences in sections 4.1.1 

and 4.1.2, respectively, into the 


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definition of ‘‘Analytical Interference.’’ 

The EPA also proposes to remove 

sections 4.1.1, 4.1.2, and 4.2. 

E. Section 5.0 (Safety) 

In this action, the EPA proposes 

updates to the language of section 5.0, 

including a recommendation to provide 

safety data sheets for gas standards to all 

personnel using the method. 

F. Section 6.0 (Equipment and Supplies) 

In this action, the EPA proposes to 

organize the equipment list in section 

6.0 into analytical instrumentation and 

sampling system components. The EPA 

also proposes to remove the 

descriptions of the following 

equipment, which are not needed to 

perform revised Method 320: 

• Calibration/Analyte Spike Assembly. 

• Mass Flow Meter. 

• Rotameter. 

• FTIR Cell Pump. 

In this action, the EPA proposes to 

revise the current descriptions for the 

equipment components shown in table 

4 of this preamble. 

TABLE 4—PROPOSED REVISIONS TO EXISTING DEFINITIONS

Equipment Revision Proposed description 

FTIR Analytical System ....... Change ‘‘FTIR Analytical System’’ to ‘‘FTIR Spectrometer,’’ clarify the description, and remove the requirement that the system include a personal computer 

and processing software.

An instrument that collects and digitizes the spectral interference pattern from an interferometer and mathematically transforms this signal into infrared frequency spectra. 

Gas Regulators .................... Clarify the description and add recommendations regarding materials of construction.A regulator used to introduce individual gas or gas mixtures from cylinders. Regulator should be constructed 

of the appropriate materials that minimize analyte adsorption and reactivity. 

Gas Sample Manifold .......... Change ‘‘Gas Sample Manifold’’ to ‘‘Gas Distribution 

Manifold’’ and clarify the description to include requirements for accurately diluting calibration gas, 

monitoring calibration gas pressure, and precisely introducing analyte spikes.

A manifold capable of delivering nitrogen or calibration 

gases through the sampling system or directly to the 

FTIR. The calibration gas manifold must provide accurate dilution of the calibration gas as necessary, 

monitor calibration gas pressure, and introduce 

analyte spikes into the sample stream (prior to the 

particulate filter) at a precise and known flowrate. 

Particulate Filters ................. Clarify the description and remove the example cited ... A glass wool plug (optional) inserted at the probe tip 

(for large particulate removal) and a filter (required) 

connected at the outlet of the heated probe and rated 

for 99% removal efficiency of 1 micron (μm) aerodynamic particulate. 

Polytetrafluoroethane Tubing Incorporate the description into a single description for 

‘‘Tubing’’.

Polytetrafluoroethane (PTFE), 316-stainless steel, or 

other inert material, of suitable length and diameter 

used to connect cylinder regulators to the gas manifold. 

Sampling Line/Heating System.Change ‘‘Sampling Line/Heating System’’ to ‘‘Sample 

Line’’ and clarify that the construction material should 

minimize adsorption of analytes and the length of line 

needed.

Heated to prevent sample condensation, and made of 

stainless steel, PTFE, or other material that minimizes adsorption of analytes. Line length should be 

the minimum necessary to reach sampling locations. 

Sample Pump ...................... Update the minimum flow rate requirements, clarify the 

options for pump placement, remove the requirement 

to record the gas cell sample pressure for pumps located downstream of the FTIR system, and remove 

the example cited.

A leak-free pump with bypass valve, capable of producing a sample flow rate equal to 5 cell volumes per 

sample cycle. The pump may be positioned upstream 

or downstream of the FTIR cell. If the pump is positioned upstream of the distribution manifold and FTIR 

system, use a heated head pump that is constructed 

from materials non-reactive with the analytes of interest. 

Sample Conditioning ............ Clarify the role of the optional sample conditioning in 

the sampling system.

An optional part of the sampling system used to dilute 

or remove particulate matter, water vapor, or other 

interfering species depending upon the source matrix 

composition. 

Sampling Probe ................... Clarify the description and remove the example for 

high-temperature stack samples and the recommendation to use a dilution probe for high-moisture sources.

Glass, stainless steel, PTFE, or other appropriate material to transport analytes to the IR gas cell. The sampling probe must be capable of sustained heating to 

prevent water condensation and adsorption of 

analytes. 

Stainless Steel Tubing ......... Incorporate the description into a single description for 

‘‘Tubing’’.

PTFE, 316-stainless steel, or other inert material, of 

suitable length and diameter used to connect cylinder 

regulators to the gas manifold. 

The EPA also proposes to add 

descriptions for the equipment 

components shown in table 5 of this 

preamble. 


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TABLE 5—PROPOSED NEW EQUIPMENT DESCRIPTIONS

Term Proposed description 

Computer/Data Acquisition 

System.

A computer with compatible FTIR software for control of the FTIR system, acquisition of infrared (IR) data, and 

analysis of resulting spectra. This system must have enough data storage space to archive all necessary infrared and meta data (see section 11.6 of this method). 

Gas Absorption Cell ............. The container through which the infrared beam interacts with the sample gas. The gas absorption cell must have 

the ability to monitor the pressure and temperature of the sample gas. 

Sampling System ................. The sampling system consists of the components listed in sections 6.2.1 through 6.2.9 of this method, validated 

as detailed in section 9.4. 

G. Section 7.0 (Reagents and Standards) 

In this action, the EPA proposes to 

rename current section 7.1 from 

‘‘Analyte(s) and Tracer Gas’’ to 

‘‘Analyte(s) and Tracer Standard Gases’’ 

and to require the use of EPA protocol 

gases (with expanded uncertainty ≤2%) 

be used for criteria pollutants. The EPA 

proposes to specify that other pollutants 

(non-criteria) be dual certified and that 

target analytes be within 25% of the 

emission source level or applicable 

compliance limit. The EPA also 

proposes to remove the suggestion 

regarding the use of sulfur hexafluoride 

(SF6) tracer gas. The EPA is specifically 

soliciting comment on the approach of 

using expanded uncertainty for criteria 

pollutants as well as not being 

prescriptive on the tracer that is used. 

In section 7.2 (Calibration Transfer 

Standard(s)), the EPA proposes to 

remove the requirements to select CTS 

according to section 4.5 of the FTIR 

Protocol and to obtain a NIST-traceable 

standard. The EPA also proposes to 

clarify that the CTS must be vendorcertified to ±2percent of the cylinder tag 

value and specifying the list of CTS 

standard gases that may be used. The 

EPA is soliciting comments regarding 

CTS gases and providing 

standardization there to ensure coverage 

over a wide wavelength range by using 

one of the listed gases. 

The EPA also proposes to change the 

name of section 7.3 from ‘‘Reference 

Spectra’’ to ‘‘Chemical Standards,’’ and 

to replace the reference to EPA reference 

spectra and procedures in the FTIR 

Protocol for preparing reference spectra 

with requirements to use NIST-certified 

or NIST-traceable, vendor-certified 

chemical standards that meet an 

accuracy specification of ±5 percent for 

preparing reference spectra. 

H. Section 8.0 (Sampling and Analysis 

Procedure) 

In this action, the EPA proposes to 

change the name of section 8.0 from 

‘‘Sampling and Analysis Procedure’’ to 

‘‘Sample Collection, Preservation, 

Storage, and Transport,’’ to clarify the 

purpose of the section in the 

introductory paragraph, and to remove 

the list of testing requirements. The EPA 

proposes to remove the 

recommendation to obtain an initial 

spectrum for determining a suitable 

operational path length and the 

reference to Figure 1 (sampling train). 

In section 8.1 (currently Pretest 

Preparations and Evaluations), the EPA 

proposes to rename the section to 

‘‘Pretest Preparations’’ and to remove 

reference to section 4 of the FTIR 

Protocol for determining the optimum 

sampling system configuration. In 

section 8.2 (Leak-Check), the EPA 

proposes to remove the hyphen from the 

section title, add a statement for the user 

to follow the leak check procedures in 

the proposed revised section 11.1 (Leak 

Check), and remove sections 8.2.1 

(Sampling System) and 8.2.2 (Analytical 

System Leak Check). 

In section 8.3 (Detector Linearity), the 

EPA proposes to replace the text with a 

statement for the user to follow the 

detector linearity verification 

procedures in proposed revised section 

11.2 (Detector Linearity). The EPA 

proposes to remove sections 8.3.1 and 

8.3.2, which provide the options to 

verify detector linearity by varying the 

power incident on the detector by 

modifying the aperture setting or by 

using neutral density filters to attenuate 

the infrared beam in current, 

respectively. The EPA also proposed to 

incorporate section 8.3.3 into the 

proposed revised section 11.2. 

For section 8.4 (Data Storage 

Requirements), the EPA proposes to 

replace the data storage requirements 

with a statement for the user to follow 

the data storage requirements in new 

proposed section 11.8 (Digital Data 

Storage). The EPA also proposes to 

remove the requirement to prepare a 

backup copy of the field test spectra and 

the requirement to record sample 

conditions, instrument settings, and test 

records. 

In section 8.5 (Background Spectra), 

the EPA proposes to remove the 

requirement to evacuate the gas cell and 

fill the cell with dry nitrogen to ambient 

pressure. The EPA also proposes to 

remove the requirement to create a 

backup copy of the background 

interferogram and processed singlebeam spectrum and remove sections 

8.5.1 (Interference Spectra) and 8.5.2 for 

collection of water vapor spectra. 

For section 8.6 (Pre-Test Calibrations), 

the EPA proposes to revise the 

requirements for the CTS in section 

8.6.1 (Calibration Transfer Standard) 

and to replace the QA spike 

requirements in section 8.6.2 (QA 

Spike) with a statement for the user to 

follow the QA spike requirements in 

new proposed section 11.4 (QA Spike). 

The EPA proposes to revise section 

8.7 (Sampling) by replacing the 

introductory paragraph with a statement 

for the user to follow the sampling 

procedures specified in new proposed 

section 11.5 (Stratification Check). The 

EPA also proposes to incorporate the 

requirements for the signal 

transmittance from section 8.9 

(Sampling QA and Reporting) into the 

introductory paragraph and to remove 

sections 8.7.1 (Batch Sampling) and 

8.7.2 (Continuous Sampling). 

For section 8.8 (Sampling QA and 

Reporting), the EPA proposes to rename 

the section ‘‘Post-Run CTS’’ and add a 

requirement to record a post-run CTS. 

The EPA proposes to incorporate the 

requirement that sample integration 

times be sufficient to achieve the 

required signal-to-noise ratio from 

section 8.8.1 into a proposed revised 

section 9.1.1.1. The EPA also proposes 

to remove sections 8.8.1, 8.8.2, 8.8.3, 

and 8.8.4 and instead specify the 

requirements to assign unique file 

names, store two copies of 

interferograms and spectra, and prepare 

sample spectrum documentation, 

respectively. 

For section 8.9 (Signal 

Transmittance), the EPA proposes to 

incorporate the requirements for the 

signal transmittance from section 8.9 

into revised section 8.7, and to replace 

the text in section 8.9 with a proposed 

requirement to perform post-run QA 

according to proposed revised section 

9.1.2 (Post-Run QA). 

In section 8.10 (Post-Test QA), the 

EPA proposes to move the post-test CTS 

requirements to new proposed section 

11.6 (Post-Test CTS). The EPA also 


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proposes to move section 8.11 (Post-Test 

QA) to proposed revised section 9.1.2 

(Post-Run QA). 

I. Section 9.0 (Quality Control) 

In this action, the EPA proposes to 

rename section 9.0 to ‘‘Quality 

Assurance and Quality Control’’ and to 

remove the introductory sentence. The 

EPA proposes to replace section 9.1 

(Spike Materials), which specifies the 

accuracy requirements for spike 

materials, with revised section 9.1 

(Quality Assurance) and to add 

requirements for performing pre-test 

QA. The EPA proposes to move the 

existing section 8.11 to the proposed 

revised section 9.1.2 and to remove the 

reference to the FTIR Protocol. 

For section 9.2 (Spiking Procedure), 

the EPA proposes to replace the spiking 

procedures with a proposed revised 

section 9.2 (Quality Control) stating that 

analyte spike procedure in new 

proposed section 9.3 (Spike Procedure) 

and the validation procedure in new 

proposed section 9.4 (Method 

Validation Procedure) evaluate the 

sampling system performance and 

quantify sampling system effects on the 

measured concentrations. The EPA also 

proposes to clarify that the method is 

self-validating, provided that the results 

meet the performance requirement of 

the QA spike in new proposed section 

11.4, and to remove the requirement 

that the results from a previous method 

validation support the use of this 

method in the application. 

J. Section 10.0 (Calibration and 

Standardization) 

In this action, the EPA proposes 

updates to section 10.0 by replacing 

section 10.1 (Signal-to-Noise Ratio) with 

a revised section 10.1 (Analytes) that 

specifies the procedures for calibrating 

and standardizing analytes, replacing 

section 10.2 (Absorbance Path Length) 

with a revised section 10.2 

(Interferents), and replacing section 10.3 

(Instrument Resolution) with revised 

section 10.3 (CTS Absorption Bands). 

The EPA proposes to replace section 

10.4 (Apodization Function) with a 

revised section 10.4 (Reference Spectra), 

which would provide users with 

procedures for collecting reference 

spectra, and to replace section 10.5 

(FTIR Cell Volume) with a revised 

section 10.5 (Absorption Cell Path 

Length Determination), which would 

specify the revised procedures for 

determining the absorption cell path 

length. The EPA also proposes to add 

new section 10.6 (Instrument 

Resolution) to revise procedures for 

determining instrument resolution. 

K. Section 11.0 (Data Analysis and 

Calculations) 

In this action, the EPA proposes to 

change the title of current section 11.0 

to ‘‘Method Procedures.’’ The EPA 

proposes to replace section 11.1 

(Spectral De-Resolution) with a revised 

section 11.1 that would provide two 

options to verify that there are no 

significant vacuum-side leaks (i.e., the 

low-flow test and the vacuum-decay 

test) and to replace section 11.2 (Data 

Analysis) with a revised section 11.2 

that would incorporate the requirements 

in the current introductory paragraph 

for section 8.3 and requirements in 

section 8.3.3. The EPA also proposes to 

add several new sections as summarized 

in table 6 of this preamble. The EPA 

requests comment on these leak check 

approaches. 

TABLE 6—PROPOSED ADDITIONS TO SECTION 11 

Section Description 

11.3 (Gas Cell Pathlength) .. Requires verification of the gas cell pathlength according to the procedures in revised section 10.6.4. 

11.4 (QA Spike) ................... Clarifies that the QA spike procedure assumes that the method has been validated for each of the target analyte 

at the source, rather than for only some of the target analytes as specified in current section 8.6.2 and presents the revised QA spike procedures for use of a certified standard or use of a non-certified standard. 

11.5 (Sampling) .................... Specifies the revised sampling procedures, including performing a stratification check. 

11.6 (Post-Test CTS) ........... Requires comparison of the pre- and post-test CTS spectra. 

11.7 (Record and Report) .... Specifies the revised recording and reporting requirements. 

11.8 (Digital Data Storage) .. Incorporates the requirements from section 8.4. 

L. Section 12.0 (Method Performance 

Data Analysis and Calculations) 

For section 12.0, the EPA proposes to 

rename the section ‘‘Data Analysis and 

Calculations’’ and to replace section 

12.1 (Spectral Quality) with a revised 

section 12.1 that specifies the required 

capabilities of the concentration 

algorithm. The EPA also proposes to 

remove section 12.2 (Sampling QA/QC). 

M. Section 13.0 (Method Validation 

Procedure) 

In this action, the EPA proposes to 

rename current section 13.0 from 

‘‘Method Validation Procedure’’ to 

‘‘Method Performance’’ and to remove 

the introductory paragraph. The EPA 

also proposes to replace section 13.1 

with a revised section 13.1 (Detection 

Level), which would include the 

proposed requirement that the detection 

level must be within 20 percent of the 

applicable compliance limit, and to 

replace section 13.2 (Batch Sampling) 

with a revised section 13.2 (Background 

Deviation), which would incorporate 

the performance criteria in the current 

definition of ‘‘Background Deviation.’’ 

N. Section 14.0 (Pollution Prevention) 

In section 14.0, the EPA proposes to 

remove the sentence describing the 

mass of HAP that may be emitted by the 

extracted sample gas for a typical 3-hour 

validation run. 

O. Section 15.0 (Waste Management) 

The EPA is not proposing any changes 

to section 15.0 in this action. 

P. Section 16.0 (References) 

In section 16.0, the EPA proposes to 

remove references 1, 2, 4, and 5 through 

7, and to add the reference citation and 

link for the FTIR Protocol (the current 

addendum to Method 320). 

Q. Section 17.0 (Tables, Diagrams, 

Flowcharts, and Validation Data) 

In this action, the EPA proposes to 

add new section 17.0, to update Figure 

1 (Extractive FTIR Sampling System), 

and to remove Table 1 (Example 

Presentation of Sampling 

Documentation) and Figure 2 

(Fractional Reproducibility). 

R. Addendum to Test Method 320 

In this action, the EPA proposes to 

remove the addendum and associated 

appendices from Method 320. The 

proposed revised section 16.0 will 

include a reference citation and link for 

the FTIR Protocol. 

IV. Statutory and Executive Order 

Reviews 

Additional information about these 

statutes and Executive orders can be 

found at https://www2.epa.gov/lawsregulations/laws-and-executive-orders. 


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A. Executive Order 12866: Regulatory 

Planning and Review and Executive 

Order 14094: Modernizing Regulatory 

Review 

This action is not a significant 

regulatory action as defined in 

Executive Order 12866, as amended by 

Executive Order 14094, and was 

therefore not subject to a requirement 

for Executive Order 12866 review. 

B. Paperwork Reduction Act (PRA) 

This action does not impose an 

information collection burden under the 

PRA. The revisions being proposed in 

this action to Method 320 do not add 

information collection requirements but 

make corrections, clarifications, and 

updates to existing testing methodology. 

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 proposed action 

will not impose any requirements on 

small entities. The proposed revisions to 

Method 320 do not impose any 

requirements on regulated entities. 

Rather, the proposed changes improve 

the quality of the results when required 

by other rules to use Method 320. 

Revisions proposed for Method 320 

allow contemporary advances in 

analysis techniques to be used. 

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. This 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 

This action does not have Tribal 

implications as specified in Executive 

Order 13175. The revisions being 

proposed in this action make 

corrections, clarifications, and updates 

to existing testing methodology. 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. 

Therefore, this action is not subject to 

Executive Order 13045 because it does 

not concern an environmental health 

risk or safety risk. Since this action does 

not concern human health, EPA’s Policy 

on Children’s Health also does not 

apply. 

H. Executive Order 13211: Actions 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 action involves technical 

standards. While the EPA identified 

ASTM D6348 as being potentially 

applicable, the Agency does not propose 

to use it. Currently, ASTM International 

(formerly the American Society for 

Testing and Materials) is revising ASTM 

D6348 (Standard Test Method for 

Determination of Gaseous Compounds 

by Extractive Direct Interface FTIR 

Spectroscopy), which specifies 

sampling and analytical procedures that 

are similar to EPA Method 320. Because 

the revised ASTM D6348 may be an 

equivalent method, the EPA will 

reconsider it when the revised ASTM 

D6348 becomes available. 

J. Executive Order 12898: Federal 

Actions To Address Environmental 

Justice in Minority Populations and 

Low-Income Populations and Executive 

Order 14096: Revitalizing Our Nation’s 

Commitment to Environmental Justice 

for All 

The EPA believes that this type of 

action does not concern human health 

or environmental conditions and, 

therefore, cannot be evaluated with 

respect to potentially disproportionate 

and adverse effects on communities 

with environmental justice concerns. 

This action would correct, update, and 

clarify Method 320 to improve the 

quality of the results when used. 

List of Subjects in 40 CFR Part 63 

Environmental protection, Air 

pollution control, Hazardous air 

pollutants, Method 320, FTIR, Test 

methods. 

Michael S. Regan, 

Administrator. 

For the reasons stated in the 

preamble, the Environmental Protection 

Agency proposes to amend title 40, 

chapter I of the Code of Federal 

Regulations as follows: 

PART 63—NATIONAL EMISSION 

STANDARDS FOR HAZARDOUS AIR 

POLLUTANTS FOR SOURCE 

CATEGORIES 

■ 1. The authority citation for part 63 

continues to read as follows: 

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

■ 2. Appendix A to part 63 is amended 

by revising Test Method 320 to read as 

follows: 

Appendix A to Part 63—Test Methods 

* * * * * 

Test Method 320—Measurement of Vapor 

Phase Organic and Inorganic Emissions by 

Extractive Fourier Transform Infrared 

(FTIR) Spectroscopy 

1.0 Scope and Application 

This method describes the extractive 

sampling and quantitative analysis of gaseous 

compounds in stationary source effluent 

using Fourier transform infrared (FTIR) 

spectrometry. Analysis procedures, quality 

control, and quality assurance requirements 

are included to assure that you, the tester, 

collect data of known and acceptable quality 

for each testing program. 

1.1 Analytes. This method is designed to 

measure individual gas phase hazardous air 

pollutants (HAPs) for which reference spectra 

have been developed. Other gas phase 

compounds can also be measured with this 

method so long as reference spectra obtained 

according to section 10.5 of this method are 

used. Candidate gaseous compounds must 

have infrared features (i.e., a non-zero dipole 

moment) to be detected using this method. 

1.2 Applicability. This method applies to 

the analysis of vapor phase compounds that 

absorb energy in the mid-infrared spectral 

region, from about 400 to 4000 cm¥1 (25 to 

2.5 mm). The method is used to determine 

compound-specific concentrations in a multicomponent gas sample extracted from a stack 

or ducted source. 

1.3 Data Quality Objectives (DQOs). 

Method 320 contains performance-based 

DQOs to provide data of known quality. With 

this method, you must evaluate the accuracy 

and precision of data in each gas matrix and 

at actual emissions concentrations that are 

encountered during its application. Data 

quality requirements include appropriate 

field evaluation procedures. 

2.0 Summary of Method 

2.1 A sample is extracted from the source 

at a constant rate. Samples are conditioned, 

if necessary, and transported via heated lines 

composed of inert material (to prevent 


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condensation of the measured compounds) 

from the source to a heated cell in the FTIR, 

wherein data are generated by directing an 

infrared beam through the sample to a 

detector. Most molecules absorb infrared 

radiation, and the absorbance occurs in a 

characteristic and reproducible pattern. FTIR 

data are transformed into a frequency-based 

spectra and curve fitting calculations (e.g., 

classical least squares, partial least squares) 

are used to determine compound quantities 

and minimize residuals. Target compound 

concentrations are determined using their 

unique infrared absorption features and 

reference calibration spectra. This method 

may be used simultaneously for multiple 

gaseous components. 

2.2 Measurement evaluation and 

validation for a source gas matrix are 

described in section 9.2 of this method. Pretest preparation and procedures are described 

in section 8.1 of this method. These 

procedures are designed to verify that an 

appropriate sampling system has been 

chosen and performs in a manner that 

provides results of known and acceptable 

quality is also discussed. Dynamic spiking is 

used to confirm target compound transport 

accuracy in potentially complex matrices. 

3.0 Definitions 

3.1 Absorbance means the negative 

logarithm of transmission represented by the 

relationship A = ¥log(I/I0), where I is the 

transmitted intensity of light, and I0 is the 

incident intensity of light upon a molecule. 

3.2 Absorptivity means the amount of 

infrared radiation absorbed by each 

molecule. 

3.3 Analyte means a compound that the 

method is intended to measure. This method 

is a multi-component method; therefore, 

several analytes may be targeted for a given 

test. 

3.4 Analyte spiking means the process of 

quantitatively adding calibration standards to 

source effluent. Analyte spiking is used to 

evaluate the ability of the sample transport 

and FTIR measurement systems to quantify 

the target analyte(s). 

3.5 Analytical algorithm means the 

method used to quantify the concentration of 

both target analyte(s) and additional 

compounds in a sample matrix that may 

introduce analytical interferences in each 

FTIR spectrum. 

3.6 Analytical interference means a 

spectral feature that complicates, and may 

even prevent, the analysis of an analyte. 

Analytical interferences can be background 

or spectral interferences. Background 

interferences result from a change in light 

throughput relative to the single beam 

background. This can be due to factors such 

as deposits on reflective surfaces and 

windows, temperature changes, a change in 

detector sensitivity, a change in infrared 

source output, or instrument electronics 

failure. Spectral interferences arise due to the 

presence of interfering compounds that have 

overlapping absorption features with the 

analytes of interest. 

3.7 Apodization means a mathematical 

transformation used to adjust the instrument 

line shape for measured peaks. There are 

various types of apodization functions; the 

most common are boxcar, triangular, HappGenzel, and Beer-Norton functions. 

3.8 Background deviation means a 

deviation from 100% transmittance in any 

region of the 100% line. 

3.9 Background spectrum means a 

spectrum taken in the absence of absorbing 

species or sample gas matrix, typically 

conducted using nitrogen or zero air. 

3.10 Bandwidth means the width of a 

spectral feature. This width is commonly 

listed as the full width at half the maximum 

of the spectral feature. 

3.11 Beam splitter means a device located 

in the interferometer that divides the 

incoming infrared radiation into two separate 

beams that travel two separate paths before 

recombination. 

3.12 Calibration transfer standard (CTS) 

means a certified gas calibration standard 

used to verify instrument stability. For the 

purposes of this method, the CTS must be 

ethylene, methane, or carbon dioxide. Other 

compounds may be used only with 

administrator approval. 

3.13 Classical least squares (CLS) means 

a method of analyzing multicomponent 

spectra by scaling reference absorbance 

spectra to unknown measured spectra. 

3.14 Double beam spectrum means a 

transmission or absorbance spectrum derived 

by dividing the sample single beam spectrum 

by the background spectrum. 

Note: The term ‘‘double-beam’’ is used 

elsewhere to denote a spectrum in which the 

sample and background interferograms are 

collected simultaneously along physically 

distinct absorption paths. In this method, the 

term denotes a spectrum in which the sample 

and background interferograms are collected 

at different times along the same absorption 

path. 

3.15 Fourier transform means a 

mathematical transform that allows the 

conversion of the detector response as a 

function of time to intensity as a function of 

frequency. 

3.16 Fundamental CTS means an NISTtraceable CTS reference spectrum with 

known temperature and pressure, that has 

been obtained using an absorption cell with 

an accurately known optical pathlength. 

3.17 Interferogram means a pattern that 

contains the effects of the wave interference 

that are produced from an interferometer. 

3.18 Interferometer means a device used 

to produce interference spectra, by dividing 

a beam of radiant energy into two or more 

paths. One path strikes a fixed mirror, and 

the second path strikes a moving mirror 

generating an optical path difference that 

varies over time between them. The 

recombined beams produce constructive and 

destructive interference as a function of 

changing pathlength. The Michelson 

interferometer, used in FTIR instruments, 

performs this function. 

3.19 Partial least squares means a method 

for analyzing multicomponent spectra by 

combining features from principal 

component and multiple regression analysis. 

It has been found to be most useful when 

predicting a set of dependent variables from 

a large set of independent variables. 

3.20 Reference spectra means a spectra of 

a pure sample gas obtained at a known 

concentration under controlled conditions of 

pressure, temperature, and pathlength. 

3.21 Resolution means the minimum 

separation that two spectral features must 

have to distinguish one feature from the 

another. 

3.22 Retardation means the optical path 

difference between two beams in an 

interferometer. 

3.23 Run means a series of samples taken 

successively from the stack or duct. A test 

normally consists of a specific number of 

runs. 

3.24 Single beam spectrum means the 

Fourier transformed interferogram 

representing detector response versus 

wavenumber. 

3.25 Test means the series of runs 

required by the applicable regulation. 

3.26 Tracer gas means a stable, nonreactive species that is easily transportable 

and can be blended in a gas cylinder with a 

target analyte to confirm the dilution ratio of 

a dynamic spike. 

3.27 Transmittance means the amount of 

infrared radiation that is not absorbed by the 

sample. Percent transmittance is represented 

by the following equation: %T = (I/I0) × 100. 

4.0 Interferences 

Interferences to precise, accurate 

measurement using FTIR include both 

analytical interferences defined in section 3.6 

of this method, and sampling system 

interferences. Sampling system interferences 

are conditions that prevent analytes from 

reaching the instrument due to factors such 

as sample line temperature, sample line 

materials, condensation, and sample 

transport time. 

5.0 Safety 

This method does not address all potential 

safety risks associated with its use. The 

hazards of performing this method are those 

associated with any stack sampling method. 

Anyone performing this method must follow 

safety and health practices consistent with 

stationary source sampling, including 

applicable legal and site-specific safety 

requirements. Many HAPs measured by this 

method are suspected toxic or hazardous and 

may present serious health risks. Exposure to 

these compounds from stack gas or from 

spiking standards should be avoided. Ensure 

safety data sheets (SDS) for gas standards are 

available to all personnel using this method. 

When using analyte standards, ensure that 

gases are properly vented and that the gas 

handling system is leak free. 

6.0 Equipment and Supplies 

The equipment and supplies described in 

this section are based on the schematic of the 

example sampling system shown in Figure 1. 

6.1 Analytical Instrumentation. 

6.1.1 Fourier Transform Infrared (FTIR) 

Spectrometer. An instrument that collects 

and digitizes the spectral interference pattern 

from an interferometer and mathematically 

transforms this signal into infrared frequency 

spectra. 

6.1.2 Computer/Data Acquisition System. 

A computer with compatible FTIR software 

for control of the FTIR system, acquisition of 

infrared (IR) data, and analysis of resulting 

spectra. This system must have enough data 


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storage space to archive all necessary infrared 

and meta data (see section 11.6 of this 

method). 

6.1.3 Gas Absorption Cell. The container 

through which the infrared beam interacts 

with the sample gas. The gas absorption cell 

must have the ability to monitor the pressure 

and temperature of the sample gas. 

6.2 Sampling System. The sampling 

system consists of the components listed in 

sections 6.2.1 through 6.2.9 of this method 

and validated as detailed in section 9.4. 

6.2.1 Sampling Probe. Glass, stainless 

steel, polytetrafluoroethane (PTFE), or other 

appropriate material to transport analytes to 

the IR gas cell. The sampling probe must be 

capable of sustained heating to prevent water 

condensation and adsorption of analytes. 

Note: High stack sample temperatures may 

require special steel or cooling of the probe. 

For very high moisture sources, it may be 

desirable to use a dilution probe. Special 

materials or configurations may be required 

for probes to traverse ducts or stacks. 

6.2.2 Particulate Filters. A glass wool 

plug (optional) inserted at the probe tip (for 

large particulate removal) and a filter 

(required) connected at the outlet of the 

heated probe and rated for 99% removal 

efficiency of 1 micron aerodynamic 

particulate. 

6.2.3 Sampling Line. Heated to prevent 

sample condensation, and made of stainless 

steel, PTFE, or other material that minimizes 

adsorption of analytes. Line length should be 

the minimum necessary to reach sampling 

locations. 

6.2.4 Sample Pump. A leak-free pump 

with bypass valve, capable of producing a 

sample flow rate equal to 5 cell volumes per 

sample cycle. The pump may be positioned 

upstream or downstream of the FTIR cell. If 

the pump is positioned upstream of the 

distribution manifold and FTIR system, use 

a heated head pump that is constructed from 

materials non-reactive with the analytes of 

interest. 

6.2.5 Gas Distribution Manifold. A 

manifold capable of delivering nitrogen or 

calibration gases through the sampling 

system or directly to the FTIR. The 

calibration gas manifold must provide 

accurate dilution of the calibration gas as 

necessary, monitor calibration gas pressure, 

and introduce analyte spikes into the sample 

stream (prior to the particulate filter) at a 

precise and known flowrate. 

6.2.6 Sample Conditioning. An optional 

part of the sampling system used to dilute or 

remove particulate matter, water vapor, or 

other interfering species depending upon the 

source matrix composition. 

6.2.7 Gas Regulator. A regulator used to 

introduce individual gas or gas mixtures from 

cylinders. Regulator should be constructed of 

the appropriate materials that minimize 

analyte adsorption and reaction with the 

regulator. 

6.2.8 Tubing. PTFE, 316-stainless steel, or 

other inert material, of suitable length and 

diameter used to connect cylinder regulators 

to the gas manifold. 

7.0 Reagents and Standards 

7.1 Analyte(s) and Tracer Standard Gases. 

Analyte(s) and tracer gases must come from 

gas cylinder(s). Criteria pollutants must use 

EPA Protocol gases, or equivalent (i.e., 

compressed gas standards with an expanded 

uncertainty of ≤2%). All other pollutants 

must use ‘‘dual certified’’ compressed gas 

standards (i.e., standards certified by two 

independent techniques). Target analyte 

concentrations should be within ±25% of the 

emission source levels or the applicable 

compliance limit unless otherwise prescribed 

in the applicable standard. If practical, the 

analyte standard cylinder shall also contain 

the tracer gas at a concentration that gives a 

measurable absorbance at a dilution factor of 

at least 10:1. 

7.2 Calibration Transfer Standard (CTS). 

The CTS standard must be NIST-traceable, 

per methods specified in the EPA 

Traceability Protocol for Assay and 

Certification of Gaseous Calibration 

Standards, to ±2% of the cylinder tag value. 

The CTS standard must be one of the 

following gases: ethylene, methane, or carbon 

dioxide. 

7.3 Chemical Standards. Chemical 

standards used to generate reference spectra 

must be NIST certified via gravimetric 

measurement, or NIST-traceable and vendorcertified accurate to within ±5%. 

8.0 Sample Collection, Preservation, 

Storage, and Transport 

8.1 Pretest Preparations. Determine the 

optimum sampling system configuration for 

measuring the target analytes. Use available 

information to make reasonable assumptions 

about moisture content and other 

interferences. 

8.1.1 Sampling System. 

8.1.1.1 Based on the source gas 

characteristics (e.g., temperature, pressure 

profiles, moisture content, target and 

interference physical characteristics, and 

particulate concentration), select the 

equipment for extracting and transporting gas 

samples. 

8.1.1.2 Select the techniques and/or 

equipment for the measurement of sample 

pressures and temperatures in the sample 

cell. 

8.1.1.3 Heat sample transport lines to 

maintain sample temperature at least 10 °F 

(5 °C) above the dew point for all sample 

constituents. Sample transport lines and 

system components must be heated 

sufficiently through their entire length to 

transport target compounds to the IR sample 

cell. 

8.1.2 Select Spectroscopic Setup. Select a 

spectroscopic configuration for the 

application. Approximate the absorption 

pathlength, sample pressure, absolute sample 

temperature, and signal integration period 

necessary for the analysis. Specify the 

nominal minimum instrumental linewidth 

(MIL) of the system. 

8.1.3 Analytical Program. 

8.1.3.1 Prepare an analysis algorithm for 

acquired spectra. Use as input, reference 

spectra of all target analytes and expected 

interferents. Include reference spectra of 

additional interferent compounds in the 

program if their presence (even if transient) 

in the samples is considered possible. The 

program output must be in ppmv (or parts 

per billion by volume [ppbv]) and must 

correct for differences between the reference 

pathlength (LR), temperature (TR), and 

pressure (PR), and the actual conditions used 

for collecting the sample spectra. 

8.1.3.2 Choose a mathematical technique 

(e.g., classical least squares, partial least 

squares, inverse least squares) for analyzing 

spectral data by comparison with reference 

spectra. 

8.1.3.3 Reference spectra incorporated in 

the program must either bracket the observed 

sample matrix concentration or use a direct 

injection to verify the calibration curve. 

Additionally, you must use a sufficient 

number (>3) of reference spectra (or reference 

spectra plus direct injection checks for low 

concentration regimes) in the bracketed range 

to demonstrate linearity in that concentration 

range. Alternatively, if the matrix 

concentration is expected to be within three 

times the detection limit of this method, you 

may use calculated reference spectra (i.e., 

HITRAN or PNNL) at the lower end of the 

bracketing range. 

8.1.3.4 Analysis regions selected for a 

target compound(s) must have an absorbance 

value of less than 1. You must select specific 

wavelengths in each region where the target 

analyte does not overlap with an interfering 

compound and use the selected wavelengths 

throughout the entire validation (section 9.4), 

QA spiking (section 11.4), and testing 

campaign. 

8.2 Leak Check. To conduct the leak 

check, follow the procedures specified in 

section 11.1. 

8.3 Detector Linearity. To verify detector 

linearity, follow the procedures specified in 

section 11.2. 

8.4 Data Storage Requirements. For these 

requirements, follow the procedures 

specified in section 11.8. 

8.5 Background Spectrum. Flow dry 

nitrogen through the gas cell and verify that 

no significant amounts of absorbing species 

are present. Collect a background spectrum, 

using a signal averaging period equal to or 

longer than that being used for averaging of 

source sample spectra. Assign a unique file 

name to the background spectrum. 

8.6 Pre-Test Calibrations. 

8.6.1 Calibration Transfer Standard. Flow 

the CTS gas through the cell and verify that 

the measured concentration is stable to 

within the uncertainty of the gas standard. 

Record the spectrum. Additionally, measure 

the linewidth of appropriate CTS band(s) to 

verify instrument resolution. Alternatively, 

compare CTS spectra to a reference CTS 

spectrum, if available, measured at the 

nominal resolution. 

8.6.2 QA Spike. Conduct a QA spike per 

the instructions in section 11.4 of this 

method. 

8.7 Sampling. See section 11.5 of this 

method. While sampling, monitor the signal 

transmittance. If the transmittance (relative to 

background) changes by 5% or more in any 

analytical spectral region, obtain a new 

background spectrum. 

8.8 Post-Run CTS. After the sampling 

run, record another CTS spectrum. 

8.9 Perform post-run QA per section 9.1.2 

of this method. 

9.0 Quality Assurance and Quality Control 

9.1 Quality Assurance (QA). 


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9.1.1 Pre-Test QA. 

9.1.1.1 Prior to testing, verify that the 

sample integration time is sufficient to 

achieve the required signal-to-noise ratio. 

9.1.1.2 Assign a unique file name to each 

spectrum. 

9.1.1.3 For reporting and recording 

requirements, see sections 11.6 and 11.7 of 

this method. 

9.1.2 Post-Test QA. 

9.1.2.1 Inspect the sample spectra 

immediately after the run to verify the gas 

matrix composition was close to the expected 

matrix composition. 

9.1.2.2 Verify that the sampling and 

instrumental parameters were appropriate for 

the actual stack conditions. For example, if 

the moisture of the sampled gas was much 

higher than anticipated, a shorter pathlength 

cell or more dilute sample may be needed. 

9.1.2.3 Compare the pre- and post-test 

CTS spectra. The peak absorbance in the preand post-test CTS must be ±5% of the mean 

value. 

9.2 Quality Control (QC). The analyte 

spike procedure in section 9.3 of this method 

and the validation procedure in section 9.4 

of this method are used to evaluate the 

performance of the sampling system and to 

quantify sampling system effects, if any, on 

the measured concentrations. This method is 

self-validating provided that the results meet 

the performance requirement of the QA spike 

in section 11.4 of this method. 

9.3 Spike Procedure. Spiking must be 

done per a standard addition procedure 

consisting of measuring the source emissions 

concentration (i.e., native source gas 

concentration), addition of reference gas, and 

measurement of the resulting standard 

addition (SA) elevated source gas 

concentration. Spiking must be done 

dynamically accounting for the spike 

dilution of sample gas with the addition of 

the reference gas. 

9.3.1 Each dynamic spike (DS) or SA 

replicate consists of a measurement of the 

source emissions concentration (native stack 

concentration) with and without the addition 

of the species of interest. With a single FTIR, 

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 

sampling system is challenged. Alternatively, 

you may use an independent FTIR and 

sampling system to measure the native 

source concentration throughout each 

standard addition. 

9.3.1.1 Pre and post-test spiking must 

consist of at least 3 replicates. A replicate is 

defined as the following measurement 

sequence: native gas concentration, SAelevated gas concentration, native gas 

concentration. In addition to the pre-test 

spike instance, spiking must also be 

performed post-test. 

9.3.1.2 It is recommended that spiking be 

performed after each run to ensure continued 

compliance with the required spike recovery 

criteria. If spiking is not performed after each 

run and the post-test spike fails, all data for 

that test are invalid. However, if spiking is 

performed after each run, data bracketed on 

each end by a successful spike are valid test 

data. 

9.3.2 Your spike gas flow rate must not 

contribute more than 10% of the total 

volumetric flow rate through the FTIR. 

9.3.3 Determine the response time (RT) of 

the system. First, inject zero air into the 

system. For standard addition RT 

determination, next measure the native stack 

concentration of the species to be spiked. The 

concentration has stabilized when variability 

appears constant for five minutes. 

9.3.4 You must determine a dilution 

factor (DF) for each dynamic spike. 

Determine the DF via a tracer, and use the 

following equation for a source where the 

tracer is not native to the source emissions: 

Where: 

Mspiked tracer = the measured diluted tracer gas 

concentration in a spiked sample. 

Ctracer spiked = the tracer gas concentration 

injected with the spike gas. 

Note: Use consistent concentration units 

for each variable in Equation 1. 

In instances where the tracer gas is native 

to the source emissions, use the following 

equation: 

Where: 

Mnative tracer = the measured tracer 

concentration present in the native 

effluent gas. 

Cnative tracer = the undiluted tracer gas 

concentration in the cylinder. 

Note: Use consistent concentration units 

for each variable in Equation 2. 

9.3.4.1 Standard Addition Response. The 

standard addition response (SAR) represents 

the difference between the measured native 

source concentration and the concentration 

measured upon introduction of the standard 

addition (source + SA) via dynamic spike. 

Calculate the SAR via the following equation: 

Where: 

MCspiked = the measured reference analyte 

concentration. 

MCnative = the measured concentration of the 

analyte in the native effluent. 

Note: Use consistent concentration units 

for each relevant variable in Equation 3. 

9.3.4.2 Effective Spike Addition. The 

effective spike addition (ESA) is the expected 

increase in the measured concentration as a 

result of injecting a spike. For the section 

11.4 QA spike, the ESA must be within 50% 

of the native stack concentration. Calculate 

the ESA with the following equation, for use 

when using a certified cylinder: 

Where: 

Cspike = the certified reference analyte 

concentration. 

When using a non-certified cylinder, replace 

the Cspike term in Equation 4, with 

MCspiked. 

Note: Use consistent concentration units 

for each relevant variable in Equation 4. 

9.3.4.3 Spike Recovery. The degree to 

which the SAR and the ESA agree represents 

the spike recovery (SR), or the ability to 

measure the spiked analyte on top of the 

amount of that analyte native to the stack. 


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DF= 

DF= 

Mspiked tracer 

C tracer spiked 

Mspiked tracer- Mnative tracer 

Cnative tracer- Mnative tracer 

Equation 1 

Equation 2 

SAR= MCspiked - (1- DF) * MCnative Equation 3 

ESA = DF * (Cspike - MCnative) Equation 4 
15112 Federal Register / Vol. 89, No. 42 / Friday, March 1, 2024 / Proposed Rules 

Spike recovery is calculated according to the 

following equation: 

9.3.4.4 Spiking Procedure for Highly 

Variable Sources. In some instances, a source 

may be encountered that is too variable for 

the procedures listed in sections 9.3 and 11.4 

of this method. A highly variable source, for 

which this procedure may be used is defined 

as a source that varies randomly and by more 

than 25% from data point to point, where 

two consecutive points are less than or equal 

to a minute apart. For these types of sources, 

the approach outlined in section 9.3.5.4.1 of 

this method may be used. 

9.3.4.4.1 Dual FTIR and Extractive 

Systems Approach. This field approach is 

performed using two independent FTIRs and 

sample extraction systems that use tubing of 

the same length and diameter and that pull 

the sample at approximately the same flow 

rate. One FTIR characterizes the fluctuations 

of the target analyte(s) over time and the 

second FTIR performs the spike recoveries. 

Note that testers can use either a single probe 

attached to both systems or separate probes 

for each system with the probe tips colocated (within 6 inches) in the sample duct. 

In either case, it is mandatory for the spike 

to occur prior to the PM filter. Perform the 

spiking procedure as follows. 

Note: This procedure assumes that the 

dilution factor is calculated as stated in EPA 

Method 320 or ASTM D6348–12e from either 

a spectroscopic tracer or metered flows. 

9.3.4.4.1.1 After positioning the FTIR 

probes accordingly, begin pulling sample gas 

into both FTIR sample analysis cells. Use the 

same sampling period and the identical 

quantification method (i.e., same reference 

spectra for construction and the same regions 

for quantification) for each FTIR. 

a. Sample the source gas stream for 

approximately 15 minutes, collecting at least 

8 spectra on each FTIR. 

b. Calculate the average concentration of 

the target analyte(s) for each FTIR. If the 

average concentrations determined using the 

two FTIRs are not within 10%, either the 

analysis routines were not identical, the 

timing was not consistent, or the sample 

system or FTIR cell in one of the FTIRs is 

reacting with the target analyte(s). Note: If the 

average concentrations are not within 10%, 

the spike recovery criterion will be more 

difficult to achieve. 

9.3.4.4.1.2 If the average concentrations 

agree within 10%, begin flow of the analyte 

spike into one of the FTIRs. At this point, the 

spiked FTIR should have a consistent offset 

to the unspiked FTIR. After this offset is 

consistent, collect a minimum of 8 data 

points. 

9.3.4.4.1.3 Calculate the difference 

between the average concentration of the 

spiked data and the average concentration of 

the unspiked data (i.e., the average 

concentration of the spike) using equation 6 

of this method. 

9.3.4.4.1.4 Calculate the recovery 

(equation 7) of the spike using the predicted 

spiked concentration by the dilution factor 

(as determined per the reference method 

used) and the resultant from Step 3 (equation 

6). 

Where: 

SV = Concentration of target analyte spiked 

into the extracted gas stream. 

Si = Individual concentration results from the 

spiked FTIR. 

n = Number of individual spiked 

concentration measurements collected. 

Up = Individual concentration results from 

the unspiked FTIR (native gas 

concentration). 

p = Number of individual, unspiked 

concentration measurements collected. 

Note: Use consistent concentration units 

for each relevant variable in Equation 6. 

Where: 

SV = Spiked concentration as calculated from 

Equation 6. 

DF = Dilution Factor as determined from 

tracer in spike gas standard or from 

flows. 

Spike Cylinder Concentration = 

Concentration of target analyte(s) from 

spike gas standard (e.g., determined from 

direct injection or from certified cylinder 

tag value). 

Note: Use consistent concentration units 

for each relevant variable in Equation 7. 

9.4 Method Validation Procedure. 

This validation procedure, which is based 

on EPA Method 301 (40 CFR part 63, 

appendix A), must be used to validate this 

method for the analytes in a gas matrix. 

Analytes that have not been validated for a 

particular source type may not be measured 

using Method 320. Validation at one source 

may also apply to another type of source, if 

it can be shown that the exhaust gas 

characteristics are similar at both sources. 

9.4.1 Use section 5.3 of Method 301 (40 

CFR part 63, appendix A), the Analyte Spike 

procedure, with these modifications. The 

statistical analysis of the results follows 

section 6.3 of EPA Method 301. Section 3 of 

this method defines terms that are not 

defined in Method 301. 

9.4.2 The analyte spike is performed 

dynamically. This means the spike flow is 

continuous and constant as spiked samples 

are measured. 

9.4.3 Introduce the spike gas at the back 

of the sample probe. 

9.4.4 Spiked effluent is carried through 

all sampling components downstream of the 

probe. 

9.4.5 A single FTIR system (or more) may 

be used to collect and analyze spectra (not 

quadruplicate integrated sampling trains). 

9.4.6 All of the validation measurements 

are performed sequentially in a single ‘‘run’’ 

(section 3.23 of this method). 

9.4.7 The measurements analyzed 

statistically are each independent (section 

3.22 of this method). 

9.4.8 A validation data set must consist of 

12 or more spike replicates. 

10.0 Calibration and Standardization 

10.1 Analytes. Select the required 

detection level (DLi) and maximum 

permissible analytical uncertainty (AUi) for 

each analyte (1 to i). The required DL must 

be equal to or greater than the method DL 

determined via section 13.1 of this method. 

Estimate, if possible, the maximum expected 

concentration for each analyte (CMAXi). The 

expected measurement range is then 

bounded by DLi and CMAXi for each analyte. 

10.2 Interferents. List all potential 

interferents applicable to your source matrix. 

Collect or obtain spectra of known and 

suspected interferences that were acquired 

using the same optical system that will be 

used in the field measurements. You may 

also use calculated spectra from sources such 

as HITRAN as long as the spectral resolution 

matches the resolution of source test sample 

spectra. These interferents must be included 

in the analytical algorithm used to fit FTIR 

spectra for quantitation. 


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SR= SAR 

ESA 

( sv ) Recover = Y (DF*Spike Cylinder Concentration) 

Equation 5 

Equation 6 

Equation 7 
Federal Register / Vol. 89, No. 42 / Friday, March 1, 2024 / Proposed Rules 15113 

10.3 CTS Absorption Bands. Absorption 

bands used for CTS quantitation must be at 

least ten times the root mean square (RMS) 

value of the noise equivalent absorbance 

(NEA) of a wavelength range nearest to that 

absorption band. This value, NEARMSCTS can 

be determined as follows: 

10.3.1 Determine the absolute noise 

equivalent absorption (NEA) for an analytical 

region by flowing nitrogen or zero air through 

the gas sample cell. The NEA is the peak-topeak noise in a spectrum resulting from 

collection of two successive background 

spectra. Therefore, collect two background 

spectra in succession while the nitrogen or 

zero air is continuously flowing through the 

cell. Note that the same averaging time must 

be used for NEA determination as will be 

used for actual sample collection. 

10.3.2 Calculate NEARMSCTS per the 

following equation: 

Where: 

NCTS = the number of absorbance points in 

the analysis region for the CTS. 

NEAi

CTS = the individual absorbance values 

of the noise spectrum in the analysis 

region, i. 

10.4 Reference Spectra. Obtain reference 

spectra for each analyte, interferant, 

surrogate, CTS, and tracer. 

10.4.1 The tester must report traceability 

and other pertinent information for each 

reference spectrum, for each compound, 

including: temperature, pressure, 

concentration, cylinder source and 

specifications, spectral regions of analysis 

used for quantitation (with specific 

wavelength ranges used), and calibration fit 

equations and correlations. 

10.4.2 If commercially prepared, or other 

available reference libraries are used to 

quantify data, the FTIR spectral resolution 

and line position, cell pathlength, 

temperature and pressure, and apodization 

function must be known and reported. 

Resolution, line position, and apodization 

function used for collection of sample spectra 

must be the same as those of the reference 

spectra used for quantitation. 

10.4.3 Reference spectra for each target 

compound must bracket the concentration of 

that compound in the sample stream. 

10.4.3.1 In the case where traceable 

reference spectra provided by the FTIR 

manufacturer do not bracket the 

concentration of a particular compound, two 

options are available. A direct injection of the 

compound of interest (NIST traceable and 

certified to ±5%) into the FTIR at a 

concentration lower than that found in the 

sample stream and within three times the 

method detection level, may be performed to 

demonstrate the appropriateness of the 

calibration line at this level. To perform this 

check, while directly injecting the compound 

of interest into the FTIR, wait for the 

concentration of the compound to stabilize. 

Once stable, verify that the concentration as 

determined via the calibration curve is 

within 10% of the cylinder value or else do 

not proceed with testing. 

10.4.3.2 Alternatively, calculated spectra, 

such as those from HITRAN or PNNL, may 

be used at the lower end of the bracketing 

range, within three times the method 

detection level, as well. 

10.4.4 Collecting Reference Spectra. In 

some cases, it may be necessary for the tester 

to collect reference spectra prior to testing. 

The procedure found in this section is to be 

used in such a case. 

10.4.4.1 Record a set of CTS spectra. 

10.4.4.2 Collect a set of the reference 

spectra at two or more concentrations in 

triplicate over the desired concentration 

range. The top of the concentration range 

must be less than 10 times that of the bottom 

of the range. 

10.4.4.3 Collect a second set of CTS 

spectra. The maximum accepted 

concentration for each compound shall be 

higher than the maximum estimated 

concentration for both analytes and known 

interferents in the effluent gas. For each 

analyte, the minimum accepted 

concentration shall be no greater than ten 

times the concentration-pathlength product 

of that analyte at its required detection limit. 

10.4.4.4 Permanently store the 

background and interferograms digitally, and 

separately. Document details of the 

mathematical process (i.e., apodization 

function) for generating the spectra from 

these interferograms. Record sample pressure 

(Pr), sample temperature (Tr), reference 

absorption pathlength (Lr), and interferogram 

signal integration period (tsr). 

10.5 Absorption Cell Path Length 

Determination. 

10.5.1 Flow the CTS through the FTIR 

cell. Once the absorbance of two consecutive 

spectra differ by less than or equal to the 

uncertainty of the cylinder standard, the CTS 

spectrum may be recorded. Note that the CTS 

gas must be one of the following gases: 

ethylene, methane, or carbon dioxide. 

10.5.2 Record a set of the absorption 

spectra of the CTS, and record the 

temperature, pressure, and concentration of 

the CTS. 

10.5.3 Record the instrument 

manufacturer’s nominal absorption 

pathlength, nominal spectral resolution, and 

the CTS signal integration period. 

10.5.4 Calculate the reference cell 

absorption pathlength, according to the 

following equation: 

Where: 

Lr = reference cell absorption pathlength. 

Lf = fundamental CTS absorption pathlength. 

Tr = absolute temperature of reference CTS 

gas. 

Tf = absolute temperature of fundamental 

CTS gas. 

Pr = absolute pressure of reference CTS gas. 

Pf = absolute pressure of fundamental CTS 

gas. 

Cr = concentration of the reference CTS gas. 

Cf = concentration of the fundamental CTS 

gas. 

{Ar/Af} = ratio of the reference CTS 

absorbance to the fundamental CTS 

absorbance, determined by classical least 

squares, integrated absorbance area, 

spectral subtraction, or peak absorbance 

techniques. 

10.6 Instrument Resolution. 

10.6.1 Flow ambient air through the gas 

cell. 

10.6.2 Verify the instrument resolution 

using a water absorbance peak near either 

1,918 cm¥1, 3,050 cm¥1, or 3,920 cm¥1. 

10.6.3 The absorbance of the peak being 

used for the resolution determination should 

be approximately 0.25 absorbance units. Mix 

additional humified air or nitrogen with the 

ambient flow, to achieve this absorbance. 

10.6.4 Record an absorbance spectrum 

and measure the FWHH of the chosen water 

peak. The measured FWHH of the water peak 

must be within 5% of the nominal 

instrument resolution to proceed with 

testing. 

11.0 Method Procedures 

11.1 Leak Check. Verify that there are no 

significant vacuum-side leaks using one of 

the leak tests described in this section. 

Perform the vacuum-side leak check after 

each installation at the sampling or 

measurement location. Leak check must be 

performed prior to the start of the field test, 

and after any relocation or maintenance to 

the sample transport system. A leak may be 

detected either by measuring a small amount 

of flow when there should be zero flow, or 

by measuring the vacuum decay rate. To test 

for leaks using loss of vacuum you must 

know the vacuum-side volume of your 

sampling system to within ±10% of its true 

volume. 


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NEAcrs _ .!:. ~f1:crs(NEAqrs)2 RMS - n,t.,J=l l Equation 8 

Equation 9 
15114 Federal Register / Vol. 89, No. 42 / Friday, March 1, 2024 / Proposed Rules 

11.1.1 Low-Flow Leak Test. Test a 

sampling system for leaks using low-flow 

measurements as follows: 

11.1.1.1 Seal the probe end of the system 

by capping or plugging the end of the sample 

probe. 

11.1.1.2 Start sampling pumps and 

operate them until the pressure stabilizes. 

11.1.1.3 Observe/measure the flow 

through the vacuum-side of the sampling 

system. A flow of less than 0.5% of the 

system’s normal in-use flow rate is 

acceptable. 

Note: For bypass systems, where the 

sample flow rate through the vacuum side of 

the sample system is greater than the FTIR 

cell flow rate, the higher flow rate (bypass 

plus analyzer/FTIR flow rate) is used as the 

in-use flow rate when calculating 

acceptability of the leak level. 

11.1.2 Vacuum-Decay Leak Test. Perform 

a vacuum-decay leak test as follows: 

11.1.2.1 Seal the probe end of the system 

as close to the probe opening as possible by 

capping or plugging the end of the sample 

probe. 

11.1.2.2 Operate all vacuum pumps. 

Draw a vacuum on the sampling system and 

let the pressure on the system stabilize. 

11.1.2.3 Turn off the sample pumps and 

seal the system under a vacuum of 250 

mmHg greater than the source static pressure. 

Record the absolute pressure and the system 

absolute temperature every 30 seconds for 5 

minutes. The leak rate must be equal to or 

less than 2.5 mmHg per minute. 

11.2 Detector Linearity. Observe the 

single beam instrument response in the 

frequency region below the detector cutoff 

(usually <400 cm¥1), where the detector 

response is known to be zero. Verify that the 

detector response is ‘‘flat’’ and equal to zero 

in this region, or at least 100 times less than 

the peak signal in the entire spectrum. If the 

response is not linear, decrease the aperture 

or attenuate the IR beam, and repeat the 

linearity check until the detector response is 

linear. 

11.3 Gas Cell Pathlength. Verify the gas 

cell pathlength of your instrument by 

following the procedure found in section 

10.6.4 of this method. 

11.4 QA Spike. This procedure assumes 

that the method has been validated for each 

of the target analytes at the source. Choose 

one of two options and perform the standard 

addition procedure listed in ection 9.3 of this 

method. 

Note: For unstable sources, QA spiking 

may be difficult. An alternative procedure for 

such a source is described in section 9.3.5.4. 

11.4.1 QA Spike Option 1. Use a certified 

standard (±2% accuracy) for an analyte that 

has been validated at the source. One may 

either spike each analyte of interest or choose 

an appropriate surrogate. An appropriate 

surrogate must have a vapor pressure that is 

less than or equal to the analyte of interest 

and be less soluble in water. The wavelength 

at which the surrogate is to be quantified 

must be reported and be within 100 

wavenumbers of a wavenumber that will be 

used to quantify the analyte of interest. 

Additionally, the pKa of a surrogate must be 

within 20% of the pKa of the analyte of 

interest. Surrogates are not allowed for the 

following analytes: formaldehyde, HCl, HF, 

NH3, and vinyl chloride. If the spike 

recovery, as calculated by Equation 5 of this 

method, is within 70–130% then proceed 

with the testing. 

11.4.2 QA Spike Option 2. Use a noncertified cylinder for an analyte that has been 

validated at the source. As with Option 1, 

one may either spike each analyte of interest 

or choose an appropriate surrogate. If the 

spike recovery, as calculated by equation 5 of 

this method, is within 90–110%, then 

proceed with the testing. 

11.5 Sampling. Sampling must be done 

using a continuous flow of source gas. 

11.5.1 Stratification Check. A 

stratification check must be performed, per 

the steps in this section, to justify sampling 

at a single location during testing. 

11.5.1.1 Use a probe of appropriate length 

to measure the analyte of interest at each of 

12 traverse points (MNi, where i = 1 to 12) 

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. 

11.5.1.2 Calculate the mean measured 

concentration for all sampling points 

(MNavg). 

11.5.1.3 Calculate the percent 

stratification (St) of each traverse point using 

the following equation: 

11.5.1.4 The gas stream is considered to 

be unstratified and you may perform 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 no more than 5.0% of 

the mean concentration. 

11.5.1.5 If the criteria for single point 

sampling is not met, but the concentration at 

each traverse point differs from the mean 

concentration by no more than 10% of the 

mean, the gas stream is considered minimally 

stratified, and you may sample using the ‘‘3- 

point short line.’’ 

11.5.1.6 If the concentration at any 

traverse point differs from the mean by more 

than 10%, the gas stream is considered 

stratified, and you must sample using the 

stratification check procedure specified in 

section 11.5.1.1 of this method. 

11.5.2 Assign a unique filename to each 

spectrum and separately to each 

corresponding interferogram. Spectra and 

interferograms must be providable in ‘‘.spc’’ 

format upon request. 

11.5.3 Temperature. The temperature of 

the gas cell must be measured directly. The 

temperature measurement device must be 

calibrated to within ±0.1 °C every 12 months. 

11.5.4 Pressure. The gas cell pressure 

must be measured empirically. The 

measurement device must be calibrated to 

within ±1 mmHg every 12 months. 

11.5.5 Inspect the sample spectra 

immediately after the run to verify that the 

gas matrix composition was close to the 

expected (assumed) gas matrix. Additionally, 

look at the residual spectra for each sample 

spectrum to confirm interferences have been 

accounted for. 

11.6 Post-Test CTS. At the end of each 

test, record another CTS spectrum. Compare 

the pre- and post-test CTS spectra. The peak 

absorbance in pre- and post-test CTS must be 

±5% of the mean value. 

11.7 Record and Report. 

11.7.1 The following must be 

documented and reported for each sample 

spectrum: sampling conditions, sampling 

time (# of scans per average and amount of 

time per scan), instrumental conditions 

(pathlength, temperature, pressure, 

resolution, laser frequency, instrument make 

and model), and spectral filename. 

11.7.2 Test Report. You must prepare a 

test report following the guidance in EPA 

Guidance Document 043 (Preparation and 

Review of Test Reports. December 1998). 

Additional minimum reporting requirements 

are listed here: 

11.7.2.1 Instrument and sampling system 

related items. 

a. Instrument make and model. 

b. Sampling line length, material, and 

temperature. 

c. Instrument resolution. 

d. Cell pathlength, pressure, and 

temperature. 

e. Laser frequency. 

f. Cylinder regulator type. 

11.7.2.2 Software/Algorithm related 

items. 

a. Gases included in the analysis 

(interferences + analytes of interest). 

b. Concentration values of reference 

spectra, as well as temperature and pressure. 

information for all interferences and analytes 

of interest. 

c. Analysis wavelength regions for each 

compound (interferences + analytes of 

interest). 

11.7.2.3 CTS, QA/QC and validation 

related items. 

a. A list of compounds that are being 

spiked. Note that Method 320 allows for use 

of qualified surrogates. Qualified surrogates 

should be appropriate for the compound 

actually being measured. It is preferable that 

the compound of interest always be spiked if 

it is available as a certified standard. 

b. Is/are the spike(s) being performed 

dynamically? 

c. Are spikes being introduced at the back 

of the sample probe and travelling through 

the entire sampling system? 

d. Are standards being used for QA spiking 

of appropriate quality? For example, (±2% for 

Protocol gases where available and ±5% for 

other certified gases? 


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Equation 11 
Federal Register / Vol. 89, No. 42 / Friday, March 1, 2024 / Proposed Rules 15115 

e. Has FTIR been validated for the source

under consideration? 

11.8 Digital Data Storage. All field test 

data must be electronically stored, readily 

available, and provided to the regulatory 

authority upon request. Stored information 

must include: sample interferograms, 

background interferograms, CTS sample 

interferograms, processed sample absorbance 

spectra, and processed CTS absorbance 

spectra. 

12.0 Data Analysis and Calculations 

12.1 Analyte concentrations must be 

measured using reference spectra as they are 

described in section 10.5 of this method. Use 

the algorithm developed in section 8.3 of this 

method to calculate the concentration of each 

species in the sample matrix as well as their 

respective residuals. Classical least squares, 

augmented classical least squares, or partial 

least squares algorithms must meet the 

following criteria: 

12.1.1 The algorithm must be capable of 

correcting for differences in gas cell 

pathlength, temperature, and cell pressure 

between sample and reference spectra. If the 

algorithm does not have this capability, 

perform this correction using equation 12: 

12.1.2 The algorithm must be capable of 

reporting spectral residuals for all 

compounds being analyzed as a function of 

its spectral fit using the techniques in section 

11.1 of this method. 

13.0 Method Performance 

13.1 Detection Level (DL). The DL of this 

method is defined as the SAR value where 

the SAR is greater than three times the 

residual value of the corresponding standard 

addition elevated concentration (MCspiked). 

The DL for this method must be less than or 

equal to 20% of the applicable compliance 

limit for the compound being measured. If 

this is not the case, Method 320 cannot be 

used for such an application. 

13.2 Background Deviation. Deviations in 

absorption greater than ±5% in an analytical 

region are unacceptable, and Method 320 

cannot be used under this condition. 

14.0 Pollution Prevention 

The extracted sample gas is vented outside 

the enclosure containing the FTIR system 

and gas manifold after the analysis. In typical 

method applications, the vented sample 

volume is a small fraction of the source 

volumetric flow and its composition is 

identical to that emitted from the source. 

When analyte spiking is used, spiked 

pollutants are vented with the extracted 

sample gas. Minimize emissions by keeping 

the spike flow off when not in use. 

15.0 Waste Management 

Small volumes of laboratory gas standards 

can be vented through a laboratory hood. 

Neat samples must be packed and disposed 

of according to applicable regulations. 

Surplus materials may be returned to 

supplier for disposal. 

16.0 References 

1. Protocol for the Use of Extractive Fourier

Transform Infrared (FTIR) Spectrometry in

Analyses of Gaseous Emissions from

Stationary Sources, https://www3.epa.gov/

ttn/emc/ftir/FTIRProtocol.pdf.

2. U.S. EPA. Method 301—Field Validation

of Pollutant Measurement Methods from

Various Waste Media, 40 CFR part 63,

appendix A.

3. EPA Traceability Protocol for Assay and

Certification of Gaseous Calibration

Standards, https://www.epa.gov/airresearch/epa-traceability-protocol-assayand-certification-gaseous-calibrationstandards.

17.0 Tables, Diagrams, Flowcharts, and 

Validation Data 

Figure 1. Schematic of FTIR Sampling 

System 

* * * * * 

[FR Doc. 2024–04359 Filed 2–29–24; 8:45 am] 

BILLING CODE 6560–50–P 


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