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Air Permitting Guidance for Using the Decision Support System

Explains the components of this tool for applicants for air operating permits and how to use each of those components.

The Decision Support System provides several Operating Permit documents linked together to aid in the Title V Operating Permit application and review process. Those documents are:

  • Rule Text
  • Requirements Reference Tables
  • Flowcharts

The purpose of the Relationship Entry Screens (RES) is to ambulate the standards for a particular rule and associate all the standard, monitoring, recordkeeping, reporting, and testing citations related to that main standard. The purpose of the flowchart is to quickly determine applicability of the rule to an emission unit. These documents are designed to provide guidance in completing Title V applications, particularly Form OP-REQ2 entitled "Negative Potentially Applicable Requirement Determinations" and Form OP-REQ3 entitled "Applicable Requirements Summary." They will also be used by the permit review engineers to review applications and draft the Title V permit, particularly Attachment A (Applicable Requirements Summary). Guidance is provided in the following areas:

Relationship Entry Screen

Relationship Entry Screen

The RES is a table containing the column headings: Standard, Monitoring/Testing, Recordkeeping, and Reporting. There is a row for each main standard. A main standard is typically the emission limitation for an emission unit during a specific operating scenario and will appear as the first entry in the standard column of each row. There may be other standards related to the main standard for that unit. A typical row of a RES will look like the following example, which is a row in a RES for main standard under 40 CFR 60.112b(a)(1) excerpted from 40 CFR Part 60, Subpart Kb.

Example of Relationship Entry Screen for main standard under 40 CFR 60.112b(a)(1)

Some important features of the table are defined below:



Denotes a citation that is "required" and is always associated with the main standard. This citation is needed in the permit to fully define the requirements for the emission unit, or is needed to provide operational flexibility. For instance, if it is determined that the unit is subject to 40 CFR 60.112b(a)(1), then that unit will subsequently be subject to all citations designated with an [R].


Denotes a citation that is "dependent" and additional information is needed to determine if the requirement is applicable. Such information may include a choice of unit attributes, monitoring, or testing. For instance, if it is determined that the unit is subject to 40 CFR 60.112b(a)(1), then that unit may be subject to some or all of the citations designated with a [D].

[GR] or [GD]

Denotes a citation that is "grouped," meaning that all citations under the grouped citation will apply as a group. The citation may either be group-required [GR] or group-dependent [GD]. If a main standard has been grouped it will appear in bold only. For example, 40 CFR 60.116b(e) appears as a group-required [GR] citation under the monitoring/testing column. Under 40 CFR 60.116b(e), there are paragraphs (1)-(3), which have been included with 40 CFR 6 0.116b(e). All the citations pertain to determining the true vapor pressure of the volatile organic compound (VOC) and have been grouped together to allow the owner/operator some flexibility in determining the true vapor pressure of the stored VOC.


Please note the [T] notation may lie in front of a citation in the Monitoring/Testing column in the RRT. This [T] notation indicates that a test which is required as an initial test or on a multi-annual basis, such as every two or five years. The [T] also serves as an aid to our enforcement personnel during their site inspections as a method of distinguishing particular varieties of Testing requirements from others.


Citations that appear indented and in braces below a dependent citation are listed to show the place in the rule where the determination of applicability can be made. If there are no braces beneath a dependent citation, the applicability determination is contained within the citation itself.

Italicized text

A related standard is a standard that is in addition to the main standard and does not replace the main standard. Related standards will appear in the standard column below the main standard. If the citation is from the same rule as the main standard, it will be italicized. If the citation is from a different rule, it will not be italicized. An example of a related standard is an emission limitation set in the main standard and the related standard contains the averaging time for measuring the emission limitation.

There are some parts of the rule that will not be included in the RES. These are identified as follows:

  • Applicability
  • Definitions
  • Site-wide Requirements
  • Past Compliance Dates
  • Delegation of Authority

Site-wide requirements are included in Form OP-REQ1 (Application/Permit-Wide Applicability Determinations) and codified in the Special Provisions subsection of the Site Operating Permit and the General Provisions in the General Operating Permit.


The flowchart is designed to determine applicability of the rule and provide the main standard citation and associated standard, monitoring, recordkeeping, reporting and testing requirements that are applicable to the emission unit. Thus, the flowchart will provide the same level of detail as the RES.


Each emission unit must flow through the flowchart separately for each operating scenario identified.

An example of a flowchart, from 40 CFR Part 63, Subpart Q, is found below. The RES for 40 CFR Part 63, Subpart Q is also provided so that the user can see the relationship between the RES and the flowchart.

Example flowchart of a flowchart, from 40CFR Part 63, Subpart Q

There are several features built into the flowchart to aid the user in making these determinations.

There are several features built into the flowchart to aid the user in making these determinations.

  • There will always be a citation somewhere below each decision box (represented by a diamond shape). This citation gives the location in the rule where the question originated. If further clarification is needed for the question in the decision box, the user can refer back to the rule text.

  • After the applicability determinations, there will either be a box that says the subpart does not apply or a box that will contain the applicable main standard and associated required citations. The main standard will appear as a red underlined citation and will be linked to the corresponding main standard row in the RES. For the Subpart Q flowchart, the main standard would be 40 CFR 63.402. These same citations will also appear in the relationship entry screen with either an [R] or [GR] preceding the citation. All these citations would be listed in Form OP-REQ3.

  • The next series of applicability questions will aid the user in determining which dependent citations apply to the affected unit. After the determination is made, there will be another box containing the applicable citations. In the Subpart Q flowchart, if initial start-up was after September 8, 1994, the affected facility would pick up the additional reporting requirement, 40 CFR 63.405(a)(2). This citation will have a [D] denotation in the relationship entry screen. This citation would also be listed in Form OP-REQ3.

  • When the flowchart is longer than one page, a connector, represented by a circle, will provide a number to continue to a different page of the flowchart. These connectors will be linked to the appropriate page in the flowchart.

  • If at any point in the flowchart an "End" box, represented by an oval, is encountered, there is no need to continue with the flowchart. All applicable citations have been determined for that specific emission unit and operating scenario.

  • Citations that are listed under the decision box that would enable a potentially affected facility to be exempted from the rule can be listed in Form OP-REQ2 (Negative Potentially Applicable Requirement Determinations). For example, if the source is not a major source or an integral part of a major source, the source is not subject to 40 CFR 63, Subpart Q. The citation 40 CFR 63.400(a) would be listed on Form OP-REQ2.