1. DEPARTMENT OF ENVIRONMENTAL PROTECTION
      2. Bureau of Air Quality
      3. TABLE OF CONTENTS
      4. I. GENERAL INTENT
      5. II. PERMITTING: POTENTIAL TO EMIT
      6. III. STATIONARY SOURCE EMISSION TESTING
      7. IV. AIR QUALITY MODELING ANALYSES
      8. V. SAMPLING
      9. VI. CONTINUOUS SOURCE MONITORING
      10. VII. ANNUAL EMISSION INVENTORY AND EMISSION STATEMENT
      11. VIII. PERIODIC COMPLIANCE REPORTING
      12. IX. EMISSION INVENTORIES CONTAINED IN STATE IMPLEMENTATION PLANS

273-4110-002 / Draft Sept. 8, 2012 / Page i
DEPARTMENT OF ENVIRONMENTAL PROTECTION
Bureau of Air Quality
DOCUMENT NUMBER:
273-4110-002
TITLE:
Air Quality Program Guidance for Determination of Significant Figures
and Timeliness of Report Submittal for Evaluation of Air Contaminant
Emissions and Concentrations
EFFECTIVE DATE:
Upon publication as final in the
Pennsylvania Bulletin
AUTHORITY:
Air Pollution Control Act (APCA), 35 P.S. Sections 4001-4015
POLICY:
Air Quality Program staff and owners or operators of stationary air
contamination sources should adhere to the procedures in this policy in all
calculations and reports related to permitting (including potential to emit
calculations), stationary source emission testing, air quality modeling
analyses, sample evaluation, continuous source monitoring, Annual
Emission Inventory and Emission Statement, periodic compliance
reporting, emission inventories contained in State Implementation Plans
(SIPs) for attainment, Reasonable Further Progress and maintenance of
National Ambient Air Quality Standards and determinations or
demonstrations of compliance.
PURPOSE:
This policy is necessary to assure the accuracy of analyses and reports and
compliance with regulations and source permit conditions. It establishes
conventions for rounding, truncation, and determination of significant
figures for determining air contaminant emissions and ambient
concentrations and timeliness criteria for demonstrations and
determinations of compliance. DEP staff will need to carefully review
source data submissions and calculations, as well as their own internal
information processing and analyses to ensure adherence with this
guidance.
APPLICABILITY:
Air quality staff and the owners and operators of air contamination sources
subject to regulation under the APCA. The guidance specifies the level of
accuracy required in various actions such as: source emission reporting,
emission limit compliance determinations and emission inventory
development.
DISCLAIMER:
The policies and procedures outlined in this guidance are intended to
supplement existing requirements. Nothing in the policies or procedures
shall affect regulatory requirements.
The policies and procedures herein are not an adjudication or a regulation.
There is no intent on the part of the Department of Environmental
Protection (DEP) to give the rules in these policies that weight or
deference. This document establishes the framework within which DEP

273-4110-002 / Draft Sept. 8, 2012 / Page ii
will exercise its administrative discretion in the future. DEP reserves the
discretion to deviate from this policy statement if circumstances warrant.
PAGE LENGTH:
14 Pages

273-4110-002 / Draft Sept. 8, 2012 / Page iii
TABLE OF CONTENTS
Page
I.
General Intent............................................................................................................................
1
II.
Permitting: Potential to Emit ....................................................................................................
1
III.
Stationary Source Emission Testing .........................................................................................
1
IV.
Air Quality Modeling Analyses ................................................................................................
5
V.
Sampling ...................................................................................................................................
6
VI.
Continuous Source Monitoring ................................................................................................
6
VII.
Annual Emission Inventory and Emission Statement ..............................................................
8
VIII. Periodic Compliance Reporting ................................................................................................
9
IX.
Emission Inventories contained in State Implementation Plans (SIPs)
for Attainment, Reasonable Further Progress and Maintenance of
National Ambient Air Quality Standards .................................................................................. 10

273-4110-002 / Draft Sept. 8, 2012 / Page 1
I.
GENERAL INTENT
The Pennsylvania Department of Environmental Protection (Department) believes that timely
and consistent determinations of air contaminant emissions and concentrations are necessary to
ensure that the air quality needs of the Commonwealth are fully met. As a result, this guidance is
intended to establish conventions for rounding, truncation and determination of significant
figures for determining air contaminant emissions and ambient concentrations, and timeliness
criteria for demonstrations and determinations of compliance.
II.
PERMITTING: POTENTIAL TO EMIT
Applicants for Plan Approvals, Operating Permits or authorizations to use General Plan
Approvals or General Operating Permits are encouraged not
to round “Potential to Emit” (PTE)
values. The Department discourages any PTE calculation, whether based on emissions test data,
emission factors or any other basis, where valid significant figures have been truncated or
additional significant figures have been added beyond those demonstrated to be valid within the
limits of dependability of the analytic or reference methods used to generate the data. In any
calculation of PTE, all known significant figures should be maintained throughout calculations,
and reported to the Department according to the established dependability of the test procedures
or references used in their generation. The only exception would be if a rounding convention
were to be implemented that resulted in a more restrictive estimate. Any rounding of source test
emissions data that would affect the status of a major source or synthetic minor source
classification determination should also be avoided.
III.
STATIONARY SOURCE EMISSION TESTING
A.
Rounding and Truncation
The Department will adhere to conventions for rounding and truncation of emissions data
established in reference test methods and regulations, to the extent that those reference
test methods or regulations may be determined by the Department to be applicable for
purposes of determining compliance with the standards being evaluated.
B.
Determination of Significant Figures
In the absence of a strictly applicable method, the Department will adhere to the Final
“Clean Air Act National Stack Testing Guidance,” issued by the United States
Environmental Protection Agency (EPA) on September 30, 2005, as the default criteria
for all required source testing and related compliance determinations, to ensure program-
wide consistency.
The “Clean Air Act National Stack Testing Guidance” refers to the June
6, 1990,
Performance Test Calculation Guidelines of William G. Laxton, Director, Technical
Support Division, and John S. Seitz, Director, Stationary Source Compliance Division,
Office of Air Quality Planning and Standards (OAQPS), EPA, which provides that all
emission standards are considered to have at least two significant figures for purposes of
compliance determination. For example, an emission limit stated as “0.1” is considered
to be “0.10” for compliance determination purposes. This approach should be considered
in evaluating any emissions testing for compliance purposes.

273-4110-002 / Draft Sept. 8, 2012 / Page 2
However, the “Clean Air Act National Stack Testing Guidance” assumes that no
emission standards exist that have more than three significant figures. Since emission
limits exist with more than three significant figures, calculated emission numbers will be
rounded to the number of significant figures in the emission limit, when using the “Clean
Air Act National Stack Testing Guidance” to determine compliance for a limit that has
four or more significant figures.
Any rounding of source test emissions data that would affect a major source or synthetic
minor source classification determination by an applicant should be avoided.
For purposes of determining compliance with emission limits established in Department
Plan Approvals, Operating Permits, General Plan Approvals, General Operating Permits
or Orders to meet performance testing requirements in Standards of Performance for New
Stationary Sources, under 40 CFR Part 60, the Department will round excess emissions
data to the same number of significant figures as used in the applicable subparts to
specify the emission limit, after conversion to the units of the standard using the
applicable conversion procedures in the subparts, in accordance with 40 CFR 60.13(h)(3).
C.
Timeliness
1.
Source Test Notification
Procedural Protocols, when required by a regulation, Plan Approval, Operating
Permit, General Plan Approval, General Operating Permit, or Order issued by the
Department, should be submitted to the Department at least 30 days prior to
source emission testing or in accordance with any other time limit specified in a
Plan Approval, Operating Permit, General Plan Approval, General Operating
Permit or Order issued by the Department, whichever is earlier, to ensure
adequate time for review. The Procedural Protocol should contain all of the
information required by the Pretest Procedural Protocols Section of the current
revision of the Department‟s Source Testing Manual, Technical
Guidance
Document number 274-0300-002. If a Procedural Protocol is not required, a test
plan should be maintained at the facility and be made available to the
Department‟s observer during the conduct of the test, unless otherwise approved
by the Department in writing before commencement of the test. A copy of the test
plan should be submitted with the final test report.
The Department‟s Regional Office with jurisdiction over the source(s) to be tested
should be notified of the anticipated testing at least 15 days in advance of the start
of testing or in accordance with any other time limit specified in a Plan Approval,
Operating Permit, General Plan Approval, General Operating Permit or Order
issued by the Department, whichever is earlier, unless specified otherwise in
applicable regulatory requirements or otherwise approved by the Department in
writing before commencement of the test. If the Department is not provided
timely notification and an opportunity to observe the source test consistent with
applicable regulatory requirements, the resulting test data may be rejected and a
new source test may be required. If this situation prevents the facility owner or
operator from completing a valid stack test within the requisite time frame, the

273-4110-002 / Draft Sept. 8, 2012 / Page 3
Department may consider the facility in violation of the requirement to conduct a
stack test to demonstrate compliance. However, if the facility owner or operator
provided timely notice and the Department did not respond or declined to observe
the test, the test results should not be rejected solely because the test was not
observed by the Department.
If the facility owner, operator or designated representative wishes to deviate from
a required test method, written approval should be obtained from the EPA or the
Department, as appropriate, in advance of the test.
For purposes of Standards of Performance for New Stationary Sources (NSPS)
and National Emission Standards for Hazardous Air Pollutants (NESHAP),
changes are divided into two categories: “minor” changes and “major”
changes
(described in the regulations as alternative or equivalent methods). Major
changes must be approved by the OAQPS, while minor changes may be approved
by the Department.
See
40 CFR § 60.8(b).
For purposes of the NESHAP Maximum Achievable Control Technology
(MACT) program, changes to test methods are divided into three categories:
“major,” “intermediate,” and “minor.” Major changes
are approved by OAQPS,
while intermediate and minor changes may be approved by the Department.
See
40 CFR § 63.91(g). Definitions of the three categories are provided in 40 CFR
§ 63.90(a).
The facility owner, operator or designated representative should receive prior
written approval for deviations from a test method from the appropriate agency.
If the deviation is to be approved by the Department, it should be in consultation
with EPA, or as otherwise required by delegation. See also “How to Review and
Issue Clean Air Act Applicability Determinations and Alternative
Monitoring,”
EPA 305-B-9-004, Section 4.2, pp. 19-22 (February 1999).
A request for a minor change or deviation from a required test method may be
submitted to the Department as part of the site-specific test protocol, while
intermediate and major changes or deviations to test methods should be requested
via written correspondence to the Department or EPA as appropriate. Requests
for all changes or deviations should document to the satisfaction of the
appropriate agency the requested change and the rationale for the change.
In addition to any deviations from required test methods, the owner or operator of
the facility should document within the test protocol any adjustments that will be
made prior to the source test such as tuning the burner or changing bags in a
baghouse. It is not necessary to describe normally scheduled periodic
maintenance that may occur in the normal course of operation and maintenance.
If an agency representative is present to observe the test, the owner or operator of
the facility also should notify the observer of such adjustments before the test
begins.

273-4110-002 / Draft Sept. 8, 2012 / Page 4
2.
Test Report
The test report should be submitted to the Department as soon as possible after
completion of the test and, at a minimum, in compliance with any underlying
regulatory requirements, within 60 days after completion of the last test run or in
accordance with any other time limit specified in a Plan Approval, Operating
Permit, General Plan Approval, General Operating Permit or Order issued by the
Department, whichever is earlier.
All submitted test reports should include information presented in the Source Test
Report Section of the Department‟s current version of the Source Testing Manual
(TGD No. 274-0300-002).
In order to facilitate the review of source test protocols and source test reports, all
submittals to the Department will be required to be made online with the
Pennsylvania Sourcetest Information Management System (PSIMS) when it
becomes available.
Pursuant to 25 Pa. Code Section 139.53(b), a complete test report should include a
summary of the emission results on the first page of the report. The test summary
results should include, at a minimum, the following information:
a.
A statement that the owner or operator has reviewed the report from the
emissions testing body and agrees with the findings.
b.
Permit number(s) and condition(s), which are the basis for the evaluation.
c.
A summary of results with respect to each applicable permit condition.
d.
A statement of compliance or non-compliance with each applicable permit
condition.
e.
A statement indicating whether each pollutant measured is within
permitted limits.
Any information determined by the Department to be missing from a test report
should be provided by the responsible official for the facility within seven days
after notification. Failure to provide the requested information within the
specified time frame may be cause to terminate review of the test report and
return it to the facility as an incomplete submission.

273-4110-002 / Draft Sept. 8, 2012 / Page 5
IV.
AIR QUALITY MODELING ANALYSES
A.
Model Input Data
1.
Model Source Data
a.
Emission Rates
Emission rate calculations for stationary point sources that are part of an
air quality modeling analysis should conform to either Table 8-1 or
Table 8-2
of the “Guideline on Air Quality Models,” codified in 40
CFR
Part 51, Appendix W. The number of significant figures in the emission
limit and operating level should be maintained throughout the emission
rate calculation.
b.
Emission Parameters
The number of significant figures in the emission parameters (i.e., stack
coordinates, base elevation, release height, exit temperature, exit velocity,
exit diameter) that are used in an air quality modeling analysis should
appropriately take into consideration the accuracy of the measurement
methods (i.e., site surveys, stack testing, etc.) used in obtaining the
parameters.
c.
Building Downwash Data
The number of significant figures in the input data for the building
downwash preprocessor should appropriately take into consideration the
accuracy of the measurement methods used in obtaining the data. The
number of significant figures produced by the building downwash
preprocessor should not be altered for model input.
2.
Model Receptor/Terrain Data
In the preprocessing of terrain data from the United States Geological Survey
(USGS), the number of significant figures in the data elements should not be
altered for preprocessing. Likewise, the number of significant figures produced
by the terrain preprocessor should not be altered for model input.
3.
Model Meteorological Data
In the preprocessing of site-specific meteorological data, the number of
significant figures should be consistent with the sensitivity of the meteorological
measurement instrumentation. In the preprocessing of surface and upper air
meteorological data from the National Climatic Data Center (NCDC), the number
of significant figures in the data elements should not be altered. The number of
significant figures produced for each meteorological variable by the preprocessor
should not be altered for model input.

273-4110-002 / Draft Sept. 8, 2012 / Page 6
B.
Model Output Data
Model results should to be rounded to the number of significant figures that is appropriate
for comparison to the applicable ambient air quality standard or limit.
V.
SAMPLING
Compliance will be determined or demonstrated by comparing the sample or test result to the
limit established in the applicable regulation, Plan Approval, Operating Permit, General Plan
Approval, General Operating Permit or Order issued by the Department.
Rounding and Truncation
The Department will adhere to any conventions for rounding and truncation of sample or test
data, established in reference test methods and regulations, to the extent that those reference test
methods or regulations may be determined by the Department to be applicable for purposes of
determining compliance with the standards being evaluated. The sample or test result is to be
rounded to the appropriate significant figures using generally accepted rounding protocols,
according to the demonstrated reliability of the sample or test method.
The sample or test result is not to be rounded to the number of significant figures used to specify
the allowable limit, but is to be rounded to the level of confidence the limits of the testing
procedure allow.
VI.
CONTINUOUS SOURCE MONITORING
A.
Rounding and Truncation
Requirements for data reduction and quality assurance in quarterly source monitoring
reports, including rounding and truncation conventions for reported data, are established
in the Continuous Source Monitoring Manual (TGD No. 274-0300-001).
The Department will adhere to any conventions for rounding or truncation of emissions
data, established in reference test methods and regulations, to the extent that those
reference test methods or regulations are determined by the Department to be applicable
to the standards being evaluated.
1.
Emissions
Unless required by an applicable regulation or specified by an applicable
reference test method, the Department will not round emissions data submitted by
source owners or operators in quarterly source monitoring reports, for purposes of
determining compliance with applicable emission limits.
For purposes of determining compliance with emission limits established in Plan
Approvals, Operating Permits or General Plan Approvals and General Operating
Permits issued by the Department to meet requirements in Standards of
Performance for New Stationary Sources, under 40 CFR Part 60, the Department
may round reported emissions data to the same number of significant figures as

273-4110-002 / Draft Sept. 8, 2012 / Page 7
used in the applicable subparts to specify the emission limit, after conversion to
the units of the standard using the applicable conversion procedures in the
subparts, in accordance with 40 CFR 60.13(h)(3).
In the absence of any other conventions established by applicable test reference
method, regulation, Plan Approval, Operating Permit, General Plan Approval,
General Operating Permit or Order issued by the Department, the following
default truncation conventions will be used to establish the number of digits to be
displayed in Quarterly Continuous Source Monitoring Reports, and used to
determine compliance with emission limits:
a.
Visible Emissions
Opacity data will be evaluated to two figures beyond the decimal point.
b.
Gaseous Emissions
(1)
Hourly Averages of emissions data will be evaluated to one
additional digit beyond the number used in the applicable
regulation, Plan Approval, Operating Permit, General Plan
Approval, General Operating Permit or Order issued by the
Department, to specify the emission limit.
(2)
Daily Averages of reported hourly emissions data will be evaluated
to one additional digit beyond the number used in the applicable
regulation, Plan Approval, Operating Permit, General Plan
Approval, General Operating Permit or Order issued by the
Department, to specify the emission limit.
(3)
Thirty-day Averages of reported hourly emissions data will be
evaluated to two additional digits beyond the number used in the
applicable regulation, Plan Approval, Operating Permit, General
Plan Approval, General Operating Permit or Order issued by the
Department, to specify the emission limit.
(4)
Daily, monthly, 365-day, 12-month or Annual Sums or Averages
of reported hourly emissions data will be evaluated to one
additional digit beyond the number used in the applicable
regulation, Plan Approval, Operating Permit, General Plan
Approval, General Operating Permit or Order issued by the
Department, to specify the emission limit.
2.
Data Availability
For purposes of determining compliance with requirements for data availability
established in 25 Pa. Code Chapter 139, Subchapter C (relating to requirements
for source monitoring for stationary sources), the calculated percentage of valid
hours reported will be rounded to the nearest whole hour, by normal arithmetic
convention.

273-4110-002 / Draft Sept. 8, 2012 / Page 8
B.
Timeliness
Quarterly Source Monitoring Report Submittal
As required by 25 Pa. Code Chapter 139, Subchapter C, quarterly source monitoring
reports must be submitted in the formats specified by the Department and according to
the schedules established in the Continuous Source Monitoring Manual (CSMM) (TGD
No. 274-0300-001), unless otherwise stipulated in a condition of a Plan Approval or
Operating Permit issued by the Department under 25 Pa. Code Chapter 127, an Order
issued under the Air Pollution Control Act, or by a specific written exception provided by
the Department. Reports not submitted in the specified formats and within the
established time limits will be considered delinquent.
The Department has established timeliness requirements for submittal of a Quarterly
Source Monitoring Report under “Record Keeping and Reporting” in the CSMM. On a
case-by-case basis, an alternative to established monitoring requirements may be
requested in accordance with provisions established in the CSMM. The Department has
the authority to determine which alternatives are applicable.
VII.
ANNUAL EMISSION INVENTORY AND EMISSION STATEMENT
A.
Rounding and Truncation
The Department may not accept any emission calculation for Annual Emission Inventory
or Emission Statement, whether based on emissions test data, emission factors or any
other basis, where valid significant figures have been truncated or additional significant
figures have been added beyond those demonstrated to be valid within the limits of
dependability of the emission factor or analytic or reference method used to generate the
data. Known valid significant figures should be maintained throughout intermediate
calculations. Emissions data should then be rounded for reporting purposes, by normal
mathematical convention, to the units specified in the Department‟s „Instructions for
Completing the Annual Emission Statement
Reporting Forms‟:
www.dep.state.pa.us/dep/deputate/airwaste/aq/emission/emission_inventory.htm
B.
Significant Figures for Reporting
1.
Criteria Pollutants and Precursors
NOx, SOx, VOC, PM10, PM2.5, ammonia (NH3) and CO emissions of 1.0 ton
per year or more per sub facility must be reported on a sub facility basis, to the
nearest hundredth (0.00) of a ton.
2.
Hazardous Air Pollutants (HAPs)
a.
HAPs should be reported individually (speciated).

273-4110-002 / Draft Sept. 8, 2012 / Page 9
b.
Except as specified in subsection c, below, any HAP emissions greater
than 0.5 ton per speciated HAP per sub facility per year should be reported
on a sub facility basis, to the nearest hundredth (0.00) of a ton.
c.
As provided in Section 112 (c) (6) of the Clean Air Act, 42 U.S.C.
Section 7412(c)(6), certain HAPs are of special concern. For these HAPs
of special concern, owners or operators of facilities should report any
emissions above the following thresholds in the units specified below, to
two decimal places:
Polychlorobiphenols (PCB)
0.01 tons/yr per sub facility
Lead (Pb)
0.01 tons/yr per sub facility
Polycyclic Organic Matter (POM)
0.01 tons/yr per sub facility
Dioxins*
0.02 pounds/yr per sub facility
Furans*
0.02 pounds/yr per sub facility
Mercury (Hg)
- non coal fired electric generating units (EGU)
0.0005 tons/yr per sub facility
- coal-fired EGUs
0.0001 tons/yr per sub facility
- all other types of sub facilities
0.01 tons/yr per sub facility
* Submit only in pounds per year
d.
Additional special reporting thresholds for HAPS of special concern may
be established by the Department by amending the Department‟s
„Instructions for Completing the Annual Emission Statement Reporting
Forms.‟
VIII. PERIODIC COMPLIANCE REPORTING
A.
Rounding and Truncation
No demonstration of compliance, whether based on emissions test data, sampling,
emission factors, mass balance calculation or any other basis, should be accepted where
valid significant figures have been truncated or additional significant figures have been
added beyond those demonstrated to be valid within the limits of dependability of the
basis of measurement or the analytic or reference methods used to generate the data. All
known significant figures should be maintained throughout calculations. After
completion of calculations, final data may be rounded by normal mathematical
convention, for reporting purposes, to a number of significant figures sufficient to allow
the Department to determine compliance in accordance with subsection VIII. B.
B.
Determination of Compliance
1.
The Department will determine compliance with emission limits or standards in
accordance with any method specified in a strictly applicable regulation,
condition of a Plan Approval or Operating Permit, provision of a Department
policy, or an Order issued by the Department.

273-4110-002 / Draft Sept. 8, 2012 / Page 10
2.
In the absence of a strictly applicable method, the Department will adhere to the
Final
“Clean Air Act National Stack Testing Guidance,”
issued by the United
States Environmental Protection Agency (EPA) on September 30, 2005, as the
default criteria for all required periodic compliance reporting and related
compliance determinations, to ensure program-wide consistency.
The “Clean Air Act National Stack Testing Guidance” refers to provisions of the
June 6, 1990 Performance Test Calculation Guidelines of William G. Laxton,
Director, Technical Support Division, and John S. Seitz, Director, Stationary
Source Compliance Division, OAQPS, EPA, which provides that all emission
standards are considered to have at least two significant figures for purposes of
compliance determination. For example, an emission limit stated as “0.1” is
considered to be “0.10” for compliance determination purposes. This approach
should be considered in evaluating any periodic compliance report for compliance
purposes.
However, the “Clean Air Act National Stack Testing Guidance” assumes that no
emission standards exist that have more than three significant figures. Since
emission limits exist with more than three significant figures, calculated emission
numbers will be rounded to the number of significant figures in the emission
limit, when using the “Clean Air Act National Stack Testing Guidance” to
determine compliance for a limit that has four or more significant figures.
IX.
EMISSION INVENTORIES CONTAINED IN STATE IMPLEMENTATION PLANS
(SIPs) FOR ATTAINMENT, REASONABLE FURTHER PROGRESS AND
MAINTENANCE OF NATIONAL AMBIENT AIR QUALITY STANDARDS
Rounding and Truncation
The Department will adhere to conventions for rounding and truncation established in reference
test methods or in federal or state regulations, to the extent that those are determined by the
Department to be applicable.
Emission inventories for these SIPs include stationary permitted point sources, stationary area
sources, and highway and nonroad emissions for both historical and future years.
A.
The historical inventories are compiled through a variety of methods, including:
1.
CEMS and annual reporting (see above) for permitted point sources,
2.
Arithmetic calculations for stationary area and some nonroad sources, and
3.
EPA-approved models for all highway and most nonroad sources.
B.
The projected future-year inventories are compiled from:
1.
Economic models,
2.
Arithmetic calculations, and

273-4110-002 / Draft Sept. 8, 2012 / Page 11
3.
EPA-approved models.
C.
All known and model-generated significant figures are maintained throughout
calculations before aggregation.
D.
Because of the extensive use of models with associated uncertainty, emissions are
generally included in attainment demonstrations with no more than one significant figure.
E.
For highway vehicle emission budgets under transportation conformity, emissions should
be calculated in grams. Conversion to tons should be performed only after emissions are
aggregated.

Back to top