[Federal Register Volume 89, Number 42 (Friday, March 1, 2024)]
[Proposed Rules]
[Pages 15101-15115]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-04359]


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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: [email protected]. 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: [email protected].

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
[micro]m 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)

[[Page 15102]]

    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
------------------------------------------------------------------------
                                                   Examples of regulated
           Category                 NAICS \a\             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,       Stationary
                                 92811, 211111,     Reciprocating
                                 211112, and        Internal Combustion
                                 622110.            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 
[email protected]. 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 
[email protected]. 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/

[[Page 15103]]

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   Analyte means a
                               320 can measure       compound that the
                               more than one         method is intended
                               analyte per test.     to measure. This
                                                     method is a multi-
                                                     component method;
                                                     therefore, several
                                                     analytes may be
                                                     targeted for a
                                                     given test.
Background Deviation........  Move the performance  Background deviation
                               criteria from the     means a deviation
                               definition to         from 100%
                               revised section       transmittance in
                               13.2 (Background      any region of the
                               Deviation).           100% line.
CTS [Calibration Transfer     Update the            Calibration transfer
 Standard] Standard.           definition to         standard (CTS)
                               remove the            means a certified
                               redundant             gas calibration
                               ``standard'' in the   standard used to
                               term and to specify   verify instrument
                               the acceptable CTS    stability. For the
                               gases.                purposes of this
                                                     method, the CTS
                                                     must be ethylene,
                                                     methane, or carbon
                                                     dioxide. Other
                                                     compounds may be
                                                     used only with the
                                                     Administrator's
                                                     approval.

[[Page 15104]]

 
Reference Spectrum..........  Change the term to    Reference spectra
                               plural (i.e.,         means a spectra of
                               ``Reference           a pure sample gas
                               Spectra''), clarify   obtained at a known
                               the definition, and   concentration under
                               remove the            controlled
                               reference to the      conditions of
                               FTIR Protocol.        pressure,
                                                     temperature, and
                                                     pathlength.
Run.........................  Replace               Run means a series
                               ``measurements''      of samples taken
                               with ``samples''      successively from
                               and remove the        the stack or duct.
                               minimum requirement   A test normally
                               specifications.       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) x 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

[[Page 15105]]

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         An instrument that
                               Analytical System''   collects and
                               to ``FTIR             digitizes the
                               Spectrometer,''       spectral
                               clarify the           interference
                               description, and      pattern from an
                               remove the            interferometer and
                               requirement that      mathematically
                               the system include    transforms this
                               a personal computer   signal into
                               and processing        infrared frequency
                               software.             spectra.
Gas Regulators..............  Clarify the           A regulator used to
                               description and add   introduce
                               recommendations       individual gas or
                               regarding materials   gas mixtures from
                               of construction.      cylinders.
                                                     Regulator should be
                                                     constructed of the
                                                     appropriate
                                                     materials that
                                                     minimize analyte
                                                     adsorption and
                                                     reactivity.
Gas Sample Manifold.........  Change ``Gas Sample   A manifold capable
                               Manifold'' to ``Gas   of delivering
                               Distribution          nitrogen or
                               Manifold'' and        calibration gases
                               clarify the           through the
                               description to        sampling system or
                               include               directly to the
                               requirements for      FTIR. The
                               accurately diluting   calibration gas
                               calibration gas,      manifold must
                               monitoring            provide accurate
                               calibration gas       dilution of the
                               pressure, and         calibration gas as
                               precisely             necessary, monitor
                               introducing analyte   calibration gas
                               spikes.               pressure, and
                                                     introduce analyte
                                                     spikes into the
                                                     sample stream
                                                     (prior to the
                                                     particulate filter)
                                                     at a precise and
                                                     known flowrate.
Particulate Filters.........  Clarify the           A glass wool plug
                               description and       (optional) inserted
                               remove the example    at the probe tip
                               cited.                (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 ([mu]m)
                                                     aerodynamic
                                                     particulate.
Polytetrafluoroethane Tubing  Incorporate the       Polytetrafluoroethan
                               description into a    e (PTFE), 316-
                               single description    stainless steel, or
                               for ``Tubing''.       other inert
                                                     material, of
                                                     suitable length and
                                                     diameter used to
                                                     connect cylinder
                                                     regulators to the
                                                     gas manifold.
Sampling Line/Heating System  Change ``Sampling     Heated to prevent
                               Line/Heating          sample
                               System'' to           condensation, and
                               ``Sample Line'' and   made of stainless
                               clarify that the      steel, PTFE, or
                               construction          other material that
                               material should       minimizes
                               minimize adsorption   adsorption of
                               of analytes and the   analytes. Line
                               length of line        length should be
                               needed.               the minimum
                                                     necessary to reach
                                                     sampling locations.
Sample Pump.................  Update the minimum    A leak-free pump
                               flow rate             with bypass valve,
                               requirements,         capable of
                               clarify the options   producing a sample
                               for pump placement,   flow rate equal to
                               remove the            5 cell volumes per
                               requirement to        sample cycle. The
                               record the gas cell   pump may be
                               sample pressure for   positioned upstream
                               pumps located         or downstream of
                               downstream of the     the FTIR cell. If
                               FTIR system, and      the pump is
                               remove the example    positioned upstream
                               cited.                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   An optional part of
                               the optional sample   the sampling system
                               conditioning in the   used to dilute or
                               sampling system.      remove particulate
                                                     matter, water
                                                     vapor, or other
                                                     interfering species
                                                     depending upon the
                                                     source matrix
                                                     composition.
Sampling Probe..............  Clarify the           Glass, stainless
                               description and       steel, PTFE, or
                               remove the example    other appropriate
                               for high-             material to
                               temperature stack     transport analytes
                               samples and the       to the IR gas cell.
                               recommendation to     The sampling probe
                               use a dilution        must be capable of
                               probe for high-       sustained heating
                               moisture sources.     to prevent water
                                                     condensation and
                                                     adsorption of
                                                     analytes.
Stainless Steel Tubing......  Incorporate the       PTFE, 316-stainless
                               description into a    steel, or other
                               single description    inert material, of
                               for ``Tubing''.       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.

[[Page 15106]]



              Table 5--Proposed New Equipment Descriptions
------------------------------------------------------------------------
             Term                         Proposed description
------------------------------------------------------------------------
Computer/Data Acquisition      A computer with compatible FTIR software
 System.                        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 vendor-certified 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 single-beam 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

[[Page 15107]]

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/laws-regulations/laws-and-executive-orders.

[[Page 15108]]

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

0
1. The authority citation for part 63 continues to read as follows:

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

0
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 [mu]m). 
The method is used to determine compound-specific concentrations in 
a multi-component 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

[[Page 15109]]

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. Pre-test 
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, Happ-Genzel, 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 NIST-traceable 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, 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.
    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) x 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

[[Page 15110]]

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 vendor-certified 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 [deg]F (5 [deg]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).

[[Page 15111]]

    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 pre- and 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, SA-elevated 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:
[GRAPHIC] [TIFF OMITTED] TP01MR24.037

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:
[GRAPHIC] [TIFF OMITTED] TP01MR24.038

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:
[GRAPHIC] [TIFF OMITTED] TP01MR24.039

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:
[GRAPHIC] [TIFF OMITTED] TP01MR24.040

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.

[[Page 15112]]

Spike recovery is calculated according to the following equation:
[GRAPHIC] [TIFF OMITTED] TP01MR24.041

    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 co-located 
(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).
[GRAPHIC] [TIFF OMITTED] TP01MR24.042

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.
[GRAPHIC] [TIFF OMITTED] TP01MR24.043

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.

[[Page 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, NEARMS\CTS\ 
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-to-peak 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 NEARMS\CTS\ per the following 
equation:
[GRAPHIC] [TIFF OMITTED] TP01MR24.044

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:
[GRAPHIC] [TIFF OMITTED] TP01MR24.045

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{time}  = 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.

[[Page 15114]]

    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 non-certified 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:
[GRAPHIC] [TIFF OMITTED] TP01MR24.046

    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 [deg]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?

[[Page 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:
[GRAPHIC] [TIFF OMITTED] TP01MR24.047

    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/air-research/epa-traceability-protocol-assay-and-certification-gaseous-calibration-standards.

17.0 Tables, Diagrams, Flowcharts, and Validation Data
[GRAPHIC] [TIFF OMITTED] TP01MR24.048

Figure 1. Schematic of FTIR Sampling System

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