Air Quality Help

The Air Emissions Guide to DAF Stationary Sources (Stationary Source Guide) provides guidance for estimating emissions for stationary sources of pollutant emissions commonly found at DAF installations. This guide provides updated emission factors and recommended calculation methodologies for these common sources associated with processes frequently occurring at DAF installations. The pollutants of concern addressed within this guide include criteria pollutants, Hazardous Air Pollutants (HAPs), Volatile Organic Compounds (VOCs), and greenhouse gases (GHGs). The June 2026 guide supersedes all prior versions of the Stationary Source Guide; older versions are considered obsolete.

The Air Emissions Guide to DAF Mobile Sources (Mobile Source Guide) provides guidance for estimating emissions for mobile sources of pollutant emissions commonly found at DAF installations. This guide provides updated emission factors and recommended calculation methodologies for processes and sources such as flight operations, Aerospace Ground Equipment (AGE) use, and both non-road vehicles/equipment and on-road vehicle operation. The pollutants of concern addressed within this guide include criteria pollutants, Hazardous Air Pollutants (HAPs), Volatile Organic Compounds (VOCs), and greenhouse gases (GHGs). The June 2026 guide supersedes all prior versions of the Mobile Source Guide; older versions are considered obsolete.

The Air Emissions Guide to DAF Transitory Sources (Transitory Source Guide) provides guidance for estimating emissions for transitory sources of pollutant emissions found at DAF installations. Transitory sources of emissions are those that are non-routine and/or seasonal sources (which may be stationary, mobile, or neither) that are short-term in nature. The sources included in this guide include bulk storage tank cleaning, seasonal equipment, fuel spills, hot mix asphalt plants, prescribed burns, wildfires, construction, site restoration/remediation, and land use changes. Transitory sources have historically often been erroneously included in stationary or mobile source air emission inventories, though these sources should only be accounted for in evaluating potential air quality impacts of proposed actions under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA); National Environmental Policy Act (NEPA); General Conformity; etc.. The pollutants addressed within this guide include criteria pollutants, Hazardous Air Pollutants (HAPs), Volatile Organic Compounds (VOCs), and greenhouse gases (GHGs). The June 2026 guide supersedes all prior versions of the Transitory Source Guide; older versions are considered obsolete.

This guidance document replaces the "DAF Greenhouse Gas (GHG) & Climate Change Assessment Guide." How to address GHGs and their impacts within the National Environmental Policy Act (NEPA) process has been bounced around with each changing Presidential Administration since 2009 through The Council on Environmental Quality (CEQ) guidance and regulations. This Guide provides up to date guidance and specific procedures on how to assess GHG emissions and impacts (e.g. climate change) associated with DAF projects (actions) within the NEPA process.

This guide provides guidance in assessing the air quality impacts associated with DAF proposed actions (activities that DAF or an instrumentality of the DAF engages in or supports in any way, e.g., construction project, permits applications, land management, etc.). The procedures in this Guide are consistent with current Federal air quality laws and regulations affecting the DAF mission including the National Environmental Policy Act as amended by the Fiscal Responsibility Act of 2023; Council on Environmental Quality (CEQ) guidance; the Clean Air Act as amended; and other related statutes, regulations, directives, and orders. This guide supersedes all previous versions.

The Evaluation of Air Force and Army Categorical Exclusions for Air Quality evaluates potential impacts to air quality (it does not account for non-air quality impacts) from each of the DAF and DA established CATEXs, and reevaluates potential extraordinary circumstances associated with the air quality impacts through an air quality extraordinary circumstances screening. This evaluation used the most current DAF standardized guidance for air emissions estimating (i.e., the Air Emissions Guide for Air Force Stationary, Mobile, and Transitory Sources), DAF emissions Insignificance Indicators, and the Air Conformity Applicability Model (ACAM). Other DoW components¡¯ CATEXs will be evaluated in future iterations of this guide.

The Air Quality Quantitative Assessment, Insignificance Indicators provides the technical basis of the DAF established significance indicators. Air emissions insignificance indicators are annual net change in emissions values that have been documented as clearly insignificant and therefore they do not cause or contribute to exceeding one or more NAAQSs. Insignificance indicators are used in NEPA/Conformity net-change inventory analyses to screen out DAF actions from further assessment when an action clearly has an insignificant impact on air quality. While insignificance indicators do not identify if actions are significant, they do allow for identifying actions that are truly de minimis or clearly insignificant impacts. This guide also discusses the assessment of greenhouse gas insignificance, which is when an action does not significantly cause or contribute to increase adverse climate change.

The PTE Guide provides standardized guidance and methodologies for establishing base-level PTE estimates for major source determinations. The guide evaluates DAF sources for physical and/or operational limitations to establish DAF-specific PTEs for individual source categories based on the Environmental Protection Agency's historic guidance and methodologies.

Most, if not all, DAF installations have some type of air permit. The permits range in complexity from a basic permit-by-rule (for small emission units) to a Title V permit (facility-wide permit for installations that are major sources). The Air Permitting Guide furnishes air quality personnel at DAF installations with the fundamental aspects of air permitting common to DAF installations. A well-written and relevant air permit simplifies the verification of compliance for both the permittee and regulating authorities, reducing the risk of noncompliance with air quality regulations.

New Source Review (NSR) is a preconstruction analysis and permitting program. When an NSR permit is required, an evaluation is necessary to ensure the most up to date pollution controls are utilized. Understanding the terms and concepts used in the NSR permitting program is essential. The Guide provides the DAF with a structured step-by-step approach for navigating through the applicability analysis and permitting complexities of NSR that are unique to DAF installations.

Most Air Force installations have some form of an Air Emission Inventory (AEI) requirement; however, preparing and updating an AEI for an Air Force installation is complex due to the unique and wide array of air emissions sources. The Air Program Information Management System (APIMS) AEI Procedures Guide provides instructions for producing a complete and accurate AEI for Air Force installations. The APIMS AEI Procedures Guide includes basic data set up along with specific instructions for most common air emission sources found on an Air Force installation. Each source category chapter details the specific data collection requirements and proper calculation methodologies specific to that air emissions source.

The purpose of the DAF Guide for boilers located at Area Sources of Hazardous Air Pollutants is to provide certain Air Force personnel (technicians, boiler operators, etc.) with a general understanding of key requirements for complying with 40 CFR 63 Subpart JJJJJJ, National Emission Standards for Hazardous Air Pollutants for Area Sources: Industrial, Commercial, and Institutional Boilers (commonly referred to as Subpart JJJJJJ). Subpart JJJJJJ applies to boilers located at commercial, industrial, and institutional Area Source facilities that burn coal, oil, biomass, or other solid and liquid non-waste materials. An "Area Source" HAP facility emits less than 10 tons per year of any single air toxic and less than 25 tons per year of any combination of air toxics.

The purpose of the United States Air Force (DAF) Stationary Internal Combustion Engine (ICE) Guide is to provide certain Air Force personnel (generator operators, Air Program Managers, etc.) with a general understanding of key requirements for complying with three interrelated stationary ICE air emission rules: National Emissions Standards for Hazardous Air Pollutants for Stationary Reciprocating Internal Combustion Engines (40 CFR Part 63, Subpart ZZZZ), New Source Performance Standards for Stationary Compression Ignition (40 CFR Part 60, Subpart IIII), and New Source Performance Standards for Stationary Spark Ignition Internal Combustion Engines (40 CFR 60, Subpart JJJJ). The DAF frequently uses stationary (e.g., remains in one location for more than 12 consecutive months) ICE to power equipment necessary to provide essential services (e.g., medical care, fire suppression) and critical mission support (e.g., flight line operations, communications).

The purpose of the DAF Guide for boilers located at Area Sources of Hazardous Air Pollutants is to provide certain Air Force personnel (technicians, boiler operators, etc.) with a general understanding of key requirements for complying with 40 CFR 63 Subpart DDDDD, National Emission Standards for Hazardous Air Pollutants for Major Sources: Industrial, Commercial, and Institutional Boilers (commonly referred to as Subpart DDDDD or Boiler MACT). A "Major Area Source" HAP facility emits 10 tons per year or more of any single air toxic and less than 25 tons or more per year of any combination of air toxics.

The United States Air Force Guide to the Mandatory Greenhouse Gas Reporting and Tailoring Rules discusses the applicability, requirements, and calculation methodologies for each rule as it pertains to the DAF. The first part of the Guide covers the Mandatory Greenhouse Gas Reporting Rule (MGHGRR) which requires large emitters of greenhouse gases (GHG) to collect GHG emissions data under a U.S. Environmental Protection Agency (EPA) reporting system. The second part of the Guide covers the "Tailoring Rule" which incorporates GHG emissions into the existing Title V and Prevention of Significant Deterioration ("PSD") permitting requirements. The Tailoring Rule regulates the same pollutants that are subject to reporting under the MGHGRR. While the court invalidated a portion of the Tailoring Rule, it held up EPA's ability to regulate GHG emissions for facilities already regulated for other pollutants under the PSD permit.

Earth's global temperature has risen by 1.5 °F over the past century, and is projected to continue to rise. Small changes in the global temperature can translate to large and potentially dangerous shifts in climate and weather on a global scale and even at the state level. Many states have seen changes in rainfall, resulting in more floods, droughts, or intense rain, as well as more frequent and severe heat waves. Click on the EPA Logo to view EPA published climate change fact sheets for each state and territory.

The first GHG Tailoring Rule Fact Sheet (May 13, 2010) summarizes the EPA's Final Rule for Step 1 and Step 2; phasing in the GHG emission thresholds, applicability, and requirements.

The first GHG Tailoring Rule Fact Sheet (May 13, 2010) summarizes the EPA's Final Rule for Step 1 and Step 2; phasing in the GHG emission thresholds, applicability, and requirements.