Clean Air Act
July 2000
Important Terms
Federal Agency Responsibility Under the CAA
Air Force Guidance
Major Provisions of the CAA
Regulatory Procedures
Impact on Air Force Operations
For More Information
Document References

A predominant portion of the nation's population is located in rapidly expanding metropolitan and urban areas. The increase in air pollution brought about by urbanization, industrial development, and the increased use of motor vehicles has resulted in dangers to the public health and welfare, including injury to agricultural crops and livestock, damage to property, and hazards to air and ground transportation. Air pollution prevention - that is, the control, reduction, or elimination of the amount of pollutants produced or created at a source - is primarily the responsibility of State and local governments. The authority for programs implemented by these agencies is derived from the federal Clean Air Act (CAA) and its amendments, which were passed to protect and enhance air quality for the benefit of the nation's public health, welfare, and productive capacity.

The Air Force (AF), like all federal agencies, must comply with the provisions of the CAA. This fact sheet provides a general overview of the provisions of the CAA for those unfamiliar with its intent and implementation. It is intended as a primer for PRO-ACT's three subject-specific fact sheets on the CAA detailing the Risk Management Program (RMP), the National Emission Standards for Hazardous Air Pollutants (NESHAPs) for Aerospace Facilities, the General Conformity Rule, and the New Source Review (NSR) Program. This fact sheet also summarizes areas of the CAA most likely to apply to AF activities, and includes document references and sources of information for those requiring more specific and detailed guidance on the various requirements of the CAA.

Important Terms
Actual Emissions are the rate of emissions from a source of any regulated pollutant, calculated using the unit's actual operating hours, production rates, and types of materials processed, stored, or combusted over a specified period of time, excluding excess emissions from a malfunction or startups and shutdowns associated with a malfunction.

Air Quality Control Region (AQCR) means a geographic area within a State, typically several counties or a large metropolitan area, within which concentrations of criteria pollutants are regulated and monitored. If the concentration of a particular criteria pollutant exceeds its corresponding National Ambient Air Quality Standard (NAAQS), the AQCR is classified as a nonattainment area for the pollutant. If the NAAQS for a pollutant is not exceeded, the AQCR is classified as an attainment area for the pollutant. Unclassifiable areas are those that cannot be classified on the basis of available information as meeting or not meeting the national primary or secondary ambient air quality standard for the pollutant. Maintenance areas are those which were formerly nonattainment areas for a criteria air pollutant, but have since achieved attainment status.

Air Toxics or Hazardous Air Pollutants (HAPs) (also referred to as Toxic Air Pollutants) means air pollutants listed in Section 112(b) of the CAA, of which there are currently 189 pollutants listed. Air toxics are emitted by a variety of industrial sources and by motor vehicles. Air toxics present a threat of adverse effects to human health and/or the environment, and may exist as particulate matter or vapors (gases). Air toxics include metals, other particles, gases adsorbed to particles, and certain vapors from fuels and other sources.

Area Source means a collection of similar emission units within a geographic area. Area sources collectively represent individual sources that are small and numerous, and that have not been inventoried as a specific point, mobile, or biogenic source. Area sources are grouped in such a way that they can be estimated collectively using one methodology. Examples of individual area sources are gasoline stations and dry cleaners. Other categories of area sources are pesticide use and consumer product use.

Attainment Area - see Air Quality Control Region.

Best Available Control Technology (BACT) means a control technology, based on the maximum degree of reduction for each regulated criteria pollutant that would be emitted from any new major stationary source in an attainment area, which the reviewing authority (on a case-by-case basis, taking into account energy, environmental, and economic impacts and other costs) determines is achievable for the new source through application of production processes or available methods, systems, and techniques, including fuel cleaning, treatment, or innovative fuel combination techniques for control of such pollutant.

Conformity, as it relates to air quality, is compliance with an implementation plan by eliminating or reducing the severity and number of violations of the NAAQS.

Criteria Pollutants are pollutants for which the Environmental Protection Agency (EPA) has promulgated a National Ambient Air Quality Standard. They include ozone [O3], lead [Pb], sulfur dioxide [SO2], particulate matter [PM10 and PM2.5], carbon monoxide [CO], and oxides of nitrogen [NOx]. Criteria pollutants are generated in large quantities by motor vehicles and industrial operations powered by fossil fuels.

[NOTE: For more about recent changes in air quality standards for ozone and particulate matter, see National Ambient Air Quality Standard (NAAQS) later in this section.]

Emissions Offsets are reductions of criteria pollutant emissions that are quantifiable, are surplus to reductions required by applicable State Implementation Plan (SIP) provisions, and are permanent within the specified timeframe.

Major Source, as defined in Title I Air Pollution Prevention and Control of the CAA means any stationary source or group of stationary sources located on one or more contiguous or adjacent properties, under common control, belonging to a single major industrial grouping (as described in the Standard Industrial Classification (SIC) Manual, 1987) and described below:

  1. In ozone nonattainment areas, sources with the potential to emit (PTE) volatile organic compounds (VOC) or oxides of nitrogen (NOx) in the following amounts:
    1. >100 tons per year (tpy) in areas classified as ''marginal'' or ''moderate,"
    2. >50 tpy in areas classified as ''serious,"
    3. >25 tpy in areas classified as ''severe,'' and
    4. >10 tpy in areas classified as ''extreme.''
  2. In ozone transport regions established pursuant to Section 184 of the CAA, sources with the PTE > 50 tpy of VOC;
  3. In CO nonattainment areas classified as ''serious,'' sources with the PTE > 50 tpy of CO and which contribute significantly to CO levels as determined under rules issued by the Administrator; and
  4. For particulate matter (PM10) nonattainment areas classified as ''serious,'' sources with the PTE > 70 tpy of PM10.
Major Stationary Source, as defined in Title 40 CFR Part 51, Subpart I, Review of New Sources and Modifications means any stationary source that (1) emits, or has the PTE, 250 tpy or more of any pollutant regulated under the CAA; (2) emits, or has the PTE, 100 tpy or more of a regulated pollutant within one of the 28 source categories listed in Table 1; or (3) as of August 7, 1980 is being regulated under Title I Air Pollution Prevention and Control of the CAA.

Examples of major stationary sources of air toxics include chemical plants, steel mills, oil refineries, and hazardous waste incinerators. Examples of major stationary sources of criteria pollutants include fossil fuel burning power plants and some metal and paper industrial facilities. Be sure to contact the base's Major Command (MAJCOM) or Regional Environmental Office (REO), or the State and local air quality authorities to ensure application of the correct section of the CAA and the correct criteria within that section to determine how a particular source/pollutant is regulated.

The EPA has prepared Major Source Guidance for Military Installations, which is the first reference to consult when an installation has a Major Stationary Source concern or question. Copies of this guidance are available from PRO-ACT or from EPA's Office of Air and Radiation (OAR) Policy and Guidance World Wide Web (WWW) site at

Mobile Sources are sources of regulated air emissions that are not fixed. Mobile sources are divided into two groups: road vehicles (cars, trucks, buses) and non-road vehicles (trains, planes, lawn mowers, aerospace ground equipment).

National Ambient Air Quality Standard (NAAQS) means a standard the EPA has promulgated pursuant to Section 109 of the CAA for each of the criteria pollutants. NAAQSs define levels of air quality that the EPA deems necessary, with an adequate margin of safety, to protect the public health (primary NAAQS), or that the EPA assesses are necessary to protect the public welfare from any known or anticipated adverse effects of a pollutant (secondary NAAQSs). EPA is required to review the NAAQSs every five years to assure that the standards provide adequate public health protections.

In 1997, the EPA published new O3 and PM10&2.5 NAAQSs after a lengthy scientific review process to be more protective of public health and the environment. PM10 refers to particles 10 microns or less in diameter and PM2.5 refers to particles 2.5 microns or less in diameter. It has been found that the smaller (or fine) particles - less than 2.5 microns in diameter - are largely responsible for the human health effects of greatest concern, as well as for visibility impairment (haze). The NAAQSs for ozone and particulate matter (including the revised NAAQS for PM10 and the new NAAQS for PM2.5) were issued as a final EPA rule on 16 September 1997 (EPA fact sheets on the new standards, and on the related Regional Haze Rule, are available on their WWW site). However, a lawsuit concerning the new NAAQSs was filed [American Trucking vs. EPA (D.C. Cir. 14 May 1994)]. The court determined that the new O3 standards were valid, but unenforceable, and they completely vacated the new PM10 standards, which means that they are essentially invalid. In reaching their decision, the court cited the lack of tools necessary to calculate emissions of PM2.5, as well as sufficient PM2.5 monitoring data. EPA has allocated funds to the States to monitor PM2.5 emissions for the next five years. At the conclusion of this monitoring period, the Clean Air Act Science Advisory Committee will assist EPA in reviewing the PM2.5 data and re-evaluate the standard.

National Emission Standard for Hazardous Air Pollutant (NESHAP) means a risk-based emission standard established prior to the 1990 CAA Amendments for asbestos, benzene, beryllium, coke oven emissions, inorganic arsenic, mercury, radionuclides, and vinyl chloride. As of 1990, NESHAP also means a technology-based emission standard reflecting Maximum Achievable Control Technologies (MACT) established for a 1990 list of 189 air toxics. All MACTs are to be published in the Federal Register by 15 November 2000. The terms "NESHAPs" and "MACT Standards" may be used interchangeably. Additional information on NESHAPs applicable to the aerospace industry can be found in PRO-ACT's NESHAP for Aerospace Facilities Fact Sheet.

New Source means any major stationary source of criteria pollutants, the construction or modification of which is commenced after the proposal or publication of an applicable New Source Performance Standard (NSPS).

New Source Performance Standard (NSPS) means a standard for emissions of criteria pollutants, applicable to a new source, which reflects the degree of emission limitation achievable through the application of the best system of emission reduction which the EPA determines has been adequately demonstrated.

Nonattainment Area - see Air Quality Control Region.

Operating Permit, as established under Title V of the Clean Air Act, is a permit that is intended to facilitate and enhance air quality planning, emission controls, compliance, and improve current emission inventories for existing and new major stationary sources.

Potential to Emit (PTE) means the maximum capacity of a stationary source to emit any air pollutant under its physical and operational design.

Precursor means a pollutant that is transformed in air to form another air pollutant. For example, precursors to the formation of ground level ozone (urban smog) include NOX and VOCs.

Prevention of Significant Deterioration (PSD) means a review and pre-construction permitting process applicable to new major stationary sources in attainment areas that restricts emissions of additional pollutants and may also allow incremental increases in emissions. PSD does not apply to mobile sources.

Site means the total of all stationary sources located on one or more contiguous or adjacent properties which are under common control of the same person (or persons).

Source Categories is a list of approximately 175 categories and subcategories of major stationary sources and area sources of air toxics. The current list of source categories may be found in a notice published in 63 Federal Register (FR) 29, 12 February 1998.

State Implementation Plan (SIP) is an EPA-approved plan developed by a State or other local governing body as required under Titles I & II of the CAA. SIPs provide for implementation, maintenance, and enforcement of NAAQSs in each AQCR.

Stationary Source means any building, structure, facility, or installation that emits or may emit any regulated air pollutant or any pollutant listed under Section 112(b), List of Pollutants, of the CAA.

Stratospheric Ozone Depletion is a form of air pollution thought to be caused by certain man-made chemicals that migrate to the upper atmosphere and react photochemically to convert stratospheric ozone to other, less beneficial, forms of oxygen. These ozone depleting substances (ODSs) are primarily organic chemicals containing chlorine, fluorine, and/or bromine which have been very useful in industry as solvents, refrigerants, and propellants. Examples include chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), carbon tetrachloride, and 1,1,1-trichloroethane (1,1,1-TCA).

Federal Agency Responsibility under the CAA
Federal facilities are not exempt from the provisions of the CAA. The following sections of the CAA apply specifically to federal agencies:

Section 118 waives federal immunity to fines and penalties from failure to comply with the CAA and States that all federal agencies will comply with federal, State, interstate, and local requirements in the same manner and to the same extent as any nongovernmental entity. (Current disputes concerning the authority of states to administer Inspection and Maintenance (I/M) programs at federal installations are expected to be resolved through future EPA rulemaking.)

Section 176 prohibits any federal department, agency, or instrumentality of the federal government from engaging in any activity which does not conform with a SIP after the SIP has been approved or promulgated.

The President has also issued two Executive Orders involving air pollution. Although neither are directly related to the CAA, they do impact Air Quality Programs at federal facilities:

Executive Order (EO) 12843, "Procurement Requirements and Policies for Federal Agencies for Ozone-Depleting Substances," 21 April 1993, requires federal agencies to implement cost-effective programs to minimize the procurement of materials that deplete stratospheric ozone, and to give preference to the procurement of alternate products.

EO 13149, "Greening the Government Through Federal Fleet and Transportation Efficiency," 22 April 2000, orders the federal government to exercise leadership in the reduction of petroleum consumption through improvements in fleet fuel efficiency and the use of alternative fueled vehicles (AFVs). (Supersedes EO 13031).

Air Force Guidance
Air Force Instruction (AFI) 32-7040, Air Quality Compliance, 9 May 1994, outlines Air Force responsibilities for complying with the CAA. This instruction requires Air Force activities to comply with all applicable federal, State, and local air quality regulations and standards. The AFI does not duplicate these standards, but is designed to provide a framework for compliance. The following guides are available to assist Air Force air program managers:
  • AF Clean Air Act Reference Guide, HQ USAF/CEV, January 1993.
  • US Air Force Guide to Air Quality Management, HQ USAF/CEV, January 1993.
  • US Air Force Conformity Guide, HQ USAF/CEV, August 1995.
  • Clean Air Act Impact Interactive Training Compact Disc - V. 1.0, HQ USAF/CEV, May 1996.
In addition, HQ USAF/ILEV has issued the following policy letters that pertain to ODSs and reduction of air pollution:
  • Air Force Ban on Purchase of Ozone Depleting Chemicals (ODCs), 7 January 1993.
  • Air Force Pollution Prevention Program, 7 January 1993.
  • Interim Air Force Contracting Policy for Elimination of Class I Ozone Depleting Substances, 26 May 1993.
  • Air Force Ozone Depleting Chemical (ODC) Interim Waiver Application, Approval Procedures, and Reporting Requirements, 14 July 1993.

Major Provisions of the Clean Air Act
The Clean Air Act (42 United States Code 7401 et seq.) has been amended several times since it was first enacted in 1963. The most significant and sweeping changes, 13 years in development, were the Clean Air Act Amendments of 1990 (PL 101-549). Title 40 Code of Federal Regulations (CFR) Parts 50-87 contain regulations promulgated under the authority of the CAA. The CAA mandates the ongoing promulgation of a variety of emission standards and controls; a rulemaking process that has been in progress for many years and is expected to extend well into the future.

The Regional Approach to Air Pollution
Attainment Areas
One of the goals of the CAA is to attain concentrations of certain air pollutants below which no adverse human health or environmental effects will be experienced. To this end, EPA promulgated NAAQS for six criteria pollutants in 1970. In attainment areas, EPA does not consider the NAAQS a ceiling to which the criteria pollutant concentration can climb. In fact, the CAA contains special provisions to prevent further deterioration of air quality in attainment areas.

The CAA recognizes the effect a stringent air quality standard can have on economic growth and development and, therefore, allows for incremental increases of certain criteria pollutants in a given attainment area. In contrast, to ensure unlimited growth is not allowed to degrade air quality, new major stationary sources in attainment areas are subject to Prevention of Significant Deterioration (PSD) regulations, which require the new source to obtain a preconstruction permit. Before obtaining the permit, a new source in an attainment area must evaluate the effect of emissions on existing levels of criteria pollutants and demonstrate it will use the Best Available Control Technology (BACT) to control all criteria pollutants it emits. In attainment areas, the new source must also undergo an air quality analysis for criteria pollutants to ensure that its BACT-controlled emissions will not cause an allowable increment to be exceeded, or the permit will not be issued.

Nonattainment Areas
Nonattainment areas are AQCRs where one or more of the NAAQS are exceeded. The Clean Air Act Amendments of 1990 contained provisions to bring all nonattainment areas into attainment for three criteria pollutants: (1) ground level ozone; (2) carbon monoxide; and (3) particulate matter, within a specified time frame. Nonattainment areas were further classified based on the extent to which they fail to meet the NAAQS for these three criteria pollutants. Emission controls for new major stationary sources in nonattainment areas become more stringent as the classification of the area becomes more severe. The nonattainment area classifications are:

  • For ozone: marginal: (0.121 up to 0.138 parts per
    million (ppm)) moderate: (0.138 up to 0.160 ppm)
    serious: (0.160 up to 0.180 ppm)
    severe: (0.180 up to 0.280 ppm)
    extreme: (0.280 ppm and above)
  • For carbon monoxide: moderate: (9.1 - 16.4 ppm)
    serious: (16.5 ppm and above)
  • For particulate matter: moderate: (initial classification for all nonattainment areas)
    serious: (areas that cannot attain NAAQS by attainment date)
New major stationary sources in nonattainment areas, or existing sources with major modifications, must also obtain a preconstruction permit and undergo a New Source Review (NSR - additional information can be found in PRO-ACT's The Clean Air Act: PSD and NSR Fact Sheet). It is important to remember that this requirement applies to process changes as well as to new construction activities (e.g., a change in paint VOC levels could trigger the requirement). A new or existing major stationary source in a nonattainment area is defined differently from a new major stationary source in an attainment area. In an ozone nonattainment area, any site that has the potential to emit the following quantities of VOCs or NOx, both precursors of ground level ozone, would be considered to be a new major source:

>100 tpy in marginal or moderate nonattainment areas.
>50 tpy in serious nonattainment areas.
>25 tpy in severe nonattainment areas.
>10 tpy in extreme nonattainment areas.
>50 tpy in ozone transport regions* (VOCs only).

*Note: A region where interstate transport of air pollutants from one or more states contributes significantly to a violation of a NAAQS in one or more other states.

In a CO nonattainment area, classified as moderate or serious, a major stationary source is one that has the PTE > 50 tpy of CO. The nonattainment area must be one in which the source contributes significantly to CO levels.

In a PM10 nonattainment area, classified as serious, a new source is one that has the potential to emit >70 tpy of PM10.

As part of the NSR, a new major stationary source seeking an operating permit in a nonattainment area must demonstrate it will achieve the Lowest Achievable Emission Rate (LAER). The LAER is the most stringent emission limitation within any State Implementation Plan, or the most stringent level of pollution control achievable in the related industry group. Economics is not a factor in implementing LAER. An area that is classified as nonattainment for one criteria pollutant can be in attainment for others. Therefore, the NSR for a new major stationary source in a nonattainment area also includes an air quality analysis for "attained" criteria pollutants (similar to the PSD process) to ensure allowable increments will not be exceeded by the new source. The CAA requires States with ozone nonattainment areas classified as moderate or worse, to impose emission controls on existing sources of VOCs and NOx. These limitations are based on Reasonably Available Control Technology (RACT). The EPA has not clearly defined RACT; however, the Agency has specified it will issue Control Technique Guidelines (CTGs) that will qualify as RACT for various types of pollutant sources. States can also determine RACTs on a case-by-case basis.

Applicants for new source preconstruction permits in ozone nonattainment areas must also demonstrate the production of a "net air quality benefit." Thus, if a new source releases any emissions, it must offset them at another source by an amount greater than the amount being released.

EPA's 22 April 1998 Potential to Emit (PTE) Guidance for Specific Source Categories is an important tool to use when conducting a new major stationary source analysis or major stationary source modification analysis as part of the NSR process. Copies of this guidance (Parts 1 & 2) are available from PRO-ACT or from EPA's OAR Policy and Guidance Memos WWW site at

Controlling Specific Source Emissions
The EPA has established uniform emission standards for over 60 specific categories of new sources such as fossil-fuel steam generators, incinerators, and petroleum dry cleaners. These standards, called New Source Performance Standards (NSPS) are nationwide, apply to all new sources within a category, and are not dependent on location. Since the pollutants typically emitted by these sources are criteria pollutants and not air toxics that must comply with MACT standards, new sources complying with NSPS must install Best Available Control Technologies (BACT) during construction.

The Air Toxics Approach
In 1970, the CAA authorized the EPA to identify hazardous air pollutants (HAPs) and establish risk-based National Emission Standards for Hazardous Air Pollutants (NESHAPs) for new and existing sources. Between 1970 and 1990, the EPA identified and published NESHAPs for only seven substances: arsenic, asbestos, benzene, beryllium, mercury, radionuclides, and vinyl chloride.

With the incorporation of the CAA amendments of 1990, the CAA now identifies 188 air toxics or HAPs. In addition, sources (major and area) of air toxics have been placed in approximately 175 categories and subcategories. The CAA requires the promulgation of technology-based emission control standards, by category, for existing and new major stationary sources of air toxics based on Maximum Achievable Control Technology (MACT). The MACT standards, which are based on the best-demonstrated control technologies and practices, are also referred to as NESHAPs. MACT standards are slightly different for new vs. existing sources, but strive to achieve the lowest emissions possible for a specific source category or subcategory. As of June 1999, EPA has issued 31 MACT standards affecting 48 categories of major stationary sources and close to 100 different air toxics.

Approaches for Protecting Stratospheric Ozone
Certain air pollutants have the capacity to cause local or global environmental harm by depleting stratospheric ozone. Stratospheric ozone depletion is thought to be caused primarily by certain manufactured chemicals released into the atmosphere. These chemicals are divided into two classes depending on their ozone-depletion potential. Class I ODSs have a high potential, while the ODS depletion potential for class II substances is lower.

EPA banned the production of all but one of the class I ODSs effective January 1996. The banned substances include all CFCs, halons, carbon tetrachloride, 1,1,1-TCA, and hydrobromofluorocarbons (HBFCs). The only class I ODS that continues to be produced is methyl bromide, which will be banned effective 1 January 2001.

Class II ODSs consist of HCFCs, which are currently used as substitutes for class I ODSs. However, HCFCs, too, have a phase-out schedule. HCFC-141b will be banned in 2003, HCFC-142b and HCFC-22 in 2020, and all other HCFCs in 2030.

The EPA has also established certification requirements for technicians who service, maintain, repair, and dispose of refrigeration and air conditioning systems containing CFCs and HCFCs. For all equipment, except motor vehicle air conditioners (MVACs), technicians must pass a certification examination, but are not required to take a training course. Technicians working on MVACs must take both a training course and pass an examination.

Another program developed in accordance with the CAA to combat ozone depletion is EPA's Significant New Alternatives Policy (SNAP) program. The objectives of SNAP are:

  • To identify substitutes for ODSs;
  • To evaluate the acceptability of these substitutes;
  • To promote the use of those substitutes believed to present lower overall risks to human health and the environment, relative to the class I and class II substances being replaced, as well as to other substitutes for the same end use; and
  • To prohibit the use of those substitutes found to increase overall risk.
The EPA intends to publish quarterly updates to the SNAP list as new substitutes are developed and approved.

On August 11, 1992, the Under Secretary of Defense directed the Defense Logistics Agency (DLA) to establish and manage a Defense Reserve of ozone depleting chemicals (ODCs) to ensure that supplies are available for mission critical uses for which acceptable substitutes have not yet been found. All waiver applications must certify that non-ODC alternatives do not exist, are not economically feasible, or that recycled ODCs cannot meet mission requirements. All mission critical applications, including those sustainable using recycled ODCs from the DLA bank, require a waiver. The process for obtaining a waiver allowing use of supplies from this reserve is outlined in Chapter 4 of Air Force Instruction (AFI) 32-7086, Hazardous Materials Management, 1 August 1997.

DoD Pilot Program for the Sale of Air Pollution Emission Reduction Incentives
In December 1998, the Deputy Under Secretary of Defense (Acquisition and Technology) (DUSD(A&T)) delegated the responsibility for implementing the Pilot Program for the Sale of Air Pollution Emission Reduction Incentives to the individual military departments. Guidance for implementing the pilot program has been developed by the military services and approved by DUSD (Environmental Security) (DUSD (ES)). The purpose of the pilot program is to encourage military facilities to reduce air pollutant emissions beyond legal requirements by affording the facilities the opportunity to retain certain financial benefits from the sale of the economic incentives. The pilot program encourages surplus emission reductions by allowing a facility to use the net proceeds from such sales, subject to certain conditions, for its environmental programs. Legislation was recently passed to extend the pilot program for two more years in the Fiscal Year 2000 Department of Defense (DoD) Omnibus Bill. A recent interpretation of this legislation has concluded that the program has been extended to include the leasing of air emission credits. An Air Force policy memorandum published by HQ USAF/ILEV on 23 May 2000 encourages installations to participate in the air emission credit program whether they choose to retain the credits for their own future use, or sell or lease the credits to another entity. Copies of "Combined Services Guidance: Pilot Program for Sales of Air Pollution Emission Reduction Incentives" and HQ USAF/ILEV "Air Emissions Credit" policy memorandum are available from PRO-ACT.

Approaches to Mobile Sources of Emissions
One of the nation's most serious air pollution problems is created from our constant and growing use of motor vehicles. The 1970 amendments to the CAA established motor vehicle emission standards for criteria pollutants and air toxics. Consequently, automobiles today produce 60 to 80 percent less pollution than in the 1960s, and lead emissions have dropped dramatically. Still, motor vehicle emissions account for up to 50% of VOCs and NOx, more than 50% of air toxics, and up to 90% of CO found in urban air.

The CAA has implemented a series of programs designed to help deal with the air pollution problems caused by mobile sources. Because the volatile components of gasoline act as precursors to urban smog formation, refiners must now formulate low-VOC gasoline for distribution and sale in these areas. Additionally, in areas where wintertime CO is a problem, refiners will have to sell gasoline with oxygen added (oxyfuel) to make the fuel burn more efficiently and reduce CO emissions. All gasolines must contain detergents to prevent build-up of engine deposits to keep engines working smoothly and burning clean. Finally, the CAA requires the installation of evaporative emission recovery nozzles in ozone nonattainment areas classified as "moderate" or "worse."

The CAA also encourages the development and sale of "clean alternative" fuels such as alcohols, compressed natural gas, liquified natural gas, and liquified petroleum gas for use in clean-fueled vehicles. Information on the Air Force Alternative Fueled Vehicles (AFV) program can be found in PRO-ACT's AFV Fact Sheet.

In addition to promoting "clean alternative" fuels, the CAA requires the development of "clean" cars, trucks, and buses. Pollution control devices in vehicles must function properly for 100,000 miles. Automakers must build cars that can use clean fuels with reduced tailpipe emissions. Automakers are also required to develop and build electric cars to be marketed in certain areas with severe air pollution problems. By 1996, all new cars met emission limits specified in the CAA. Also, fleet operators (10 or more heavy-duty vehicles or light-duty passenger cars or trucks) in 22 designated cities with urban smog problems are required to purchase "clean" cars. Finally, new large diesel trucks and buses are being built to reduce soot and particle emissions by at least 90 percent.

Inspection and Maintenance (I/M) Programs - In accordance with EPA national policy, and to ensure that the implementation of clean fuel and clean car programs are effective, vehicle I/M programs are being implemented by States in many nonattainment metropolitan areas. To address a dispute involving some State I/M programs and their jurisdiction over federal vehicle fleets, EPA has published draft guidance to assist federal facilities in meeting the CAA I/M program requirements. Copies of the draft guidance, "Interim Guidance for Federal Facility Compliance with CAA Sections 118(c) and 118(d) and Applicable Provisions of State Vehicle I/M Programs," are available from PRO-ACT.

General Conformity - As discussed above, the fundamental method by which the EPA tracks compliance with NAAQSs is through the designation of areas as attainment, nonattainment, maintenance, or unclassifiable. Air Force installations operating in nonattainment or maintenance areas must conform to the applicable SIP. On 30 November 1993, EPA finalized Determining Conformity of General Federal Actions to State or Federal Implementation Plans (58 FR 63247), a rule intended to ensure that federal actions do not adversely affect the timely attainment and maintenance of regional air quality standards. The Air Force is responsible for making its own conformity determinations prior to commencement of a potentially regulated action. A conformity analysis is conducted to examine the impacts of the direct and indirect air emissions from a proposed Air Force action and determines whether the action conforms to the applicable SIP. Each conformity analysis requires extensive coordination with federal, State, and Air Force officials (especially legal staff) to ensure proper compliance.

A detailed guide has been developed by Headquarters United States Air Force, Office of the Civil Engineer, Environmental Directorate (HQ USAF/CEV) entitled U.S. Air Force Conformity Guide, dated August 1995. The guide discusses, in part, when a conformity determination is required, a choice of methods for showing a positive conformity, excluded categories, air quality modeling, and typical emission rates for AF activities. A copy of this guide is available from PRO-ACT and is also available for viewing at

The Risk Management Approach
Section 112(r) of the Clean Air Act requires certain regulated facilities to develop risk management programs in order to prevent accidental releases to the atmosphere of dangerous chemicals in a process. Facilities were to submit risk management plans (RMPs) to the Environmental Protection Agency by 21 June 1999. The RMPs will then become electronically available to State and local governments and citizens to help them understand chemical hazards in their communities and take steps to prevent and respond to accidents. After 21 June 1999, RMPs are required to be complete before a new covered process is started. Updates are required every five years, or when a change occurs. Other deadlines apply for newly regulated substances and for changes to a covered process.

Regulatory Procedures
State Implementation Plans
Under the CAA, the EPA establishes the minimum requirements for achieving acceptable national air quality. This ensures all individuals will have the same basic health and environmental protection. The actual implementation of the CAA, however, lies with the States, primarily because addressing air pollution problems often requires local knowledge of industry, geography, climate, and demographics. To implement the CAA, each State must develop, and obtain EPA approval for, a State Implementation Plan (SIP).

Since each SIP is tailored for a particular State or region, they will differ from State to State, and in some States, from region to region. In some cases, States enact more stringent air pollution control regulations than those at the federal level. Under no circumstances, however, can SIPs require weaker pollution controls than those established by the EPA.

[NOTE: Air Force installations should proactively ensure that "emissions budgets" as specified in the applicable SIP include line item allocations for direct and indirect emissions from the base. This will make conformity determinations easier.]

Operating Permits
Title V of the CAA requires all States to develop operating permit programs that meet certain federal criteria. The States, in turn, require major stationary sources of air pollution to obtain permits that detail all CAA requirements applicable to the source. The permits are designed to enhance the ability of the EPA, State, and local regulatory agencies and private citizens to monitor and enforce CAA requirements. The permits will identify the pollutants emitted by a source, specify enforceable emission limits and standards, contain compliance schedules, emission monitoring requirements and reporting requirements, as well as any other conditions necessary to assure compliance. The States will charge each source an annual emission fee to cover the costs of administering the program. The recommended minimum is $25.00 per ton for each pollutant emitted.

Impact on Air Force Operations
Common sources of air pollution at Air Force installations include boilers, incinerators, fuel storage and transportation, parts cleaning, surface coating operations, and aircraft operations. The extent to which the CAA affects the operation of an Air Force facility will depend on the location of the installation and the types of industrial operations. If it is located in a nonattainment area, the installation will have to comply with strict regulations governing emissions from major stationary sources and the use of alternative fuels.

To date, NESHAPs or MACT Standards possibly having an effect on Air Force facilities have been promulgated for the following source categories:

  • Aerospace Manufacturing and Rework Facilities;
  • Chromium Electroplating and Chromium Anodizing Tanks;
  • Industrial Process Cooling Towers;
  • Perchloroethylene (PCE) Dry Cleaning Facilities;
  • Offsite Waste and Recovery Operations; and
  • Halogenated Solvent Cleaning.
Some of the NESHAPs scheduled for promulgation in the near future include those for the following categories:
  • Industrial Combustion Coordinated Rulemaking for Industrial Boilers, Institutional/Commercial Boilers, Process Heaters, and Stationary Internal Combustion Engines, and Stationary Turbines;
  • Organic Liquids Distribution (Non-gas);
  • Rocket Engine Test Firing;
  • Engine Test Facilities;
  • Paint Stripping Operations;
  • Site Remediation;
  • Reinforced Plastic Composites Production;
  • Asphalt Concrete Manufacturing;
  • Publicly Owned Treatment Works; and
  • Research and Development.
For more information on air toxics rule development and implementation, visit EPA's "Unified Air Toxics Website" at

Installations located in areas affected by the acid air pollution provisions of the CAA may have higher utility costs due to the increased emission control requirements placed on utility plants in the region.

Air Force installation managers are responsible for ensuring compliance with the CAA and are subject to strict enforcement actions. The burden of proof of compliance rests with the installation. All new sources at military installations, regardless of their location, will be required to submit to the NSR and PSD provisions of the CAA to obtain pre-construction and operating permits.

For More Information
The Environmental Protection Agency (EPA) maintains a comprehensive WWW site with links to a large variety of up-to-date regulatory and technical information pertinent to the Clean Air Act. The primary site for this information is EPA's Office of Air and Radiation WWW site located at In-depth coverage is available on a variety of topics including air quality trends, fuel economy, energy conservation, ozone depletion, air quality standards, acid rain, air toxics, and new legislation.

The Environmental Quality Directorate, Headquarters Air Force Center for Environmental Excellence (HQ AFCEE/EQ) offers program assistance and technical support to assist installation personnel with their pollution prevention and compliance needs. HQ AFCEE/EQT air quality experts include Ms. Teresa Green, DSN 240-6410, and Mr. William Moritz, DSN 240-6412.

The AFCEE P2 Resource Compact Disc (CD), Version 4.0, December 1999, is available from PRO-ACT. The P2 CD contains a large collection of documents, handbooks, and other resources to aid Air Force personnel in their P2 and compliance efforts. The P2 CD contains a number of air quality resources including handbooks and guides pertinent to hazardous air pollutants, fleet motor pools, CAA programming guidance, ODSs and the EPA SNAP program, setting MACT standards, as well as a toxic chemical air dispersion model.

The Environmental Conservation and Planning Directorate (HQ AFCEE/EC) provides support for the Air Force Environmental Impact Analysis Process (EIAP) and the Air Force Natural and Cultural Resources programs. Mr. Frank Castaneda, DSN 240-4202, can assist base-level personnel with air modeling and general conformity issues.

The AFCEE Regional Environmental Offices (REOs) play an important mediating role between Air Force installations and the States regarding the Clean Air Act. The REOs are located in San Francisco, CA; Dallas, TX; and Atlanta, GA. Services offered by the REOs include:

  • Coordinate with Air Force and other Department of Defense environmental personnel and regulatory agencies to identify regulatory issues and training opportunities;
  • Review existing and proposed federal and State agency policies, programs, regulations, and standards to determine impact on the Air Force and, as necessary, prepare, coordinate, and submit comments on proposed regulations that impact the Air Force;
  • Oversee Air Force compliance with State environmental program requirements to track status and to identify potential compliance problems;
  • Advise and assist MAJCOMs in determining regulatory requirements and in developing strategies for complying with environmental regulations and standards; and
  • Coordinate with HQ USAF, the MAJCOMs, and other staff members, as necessary, to present Air Force environmental strategies to regulatory agencies, resolve conflicts, and reach agreement on proposed compliance actions.
More Information about the Regional Environmental Offices, including contact information and maps of the regions covered by each REO, is available at AFCEE's WWW site:

The Defense Environmental Network & Information eXchange (DENIX) provides DoD personnel with timely access to environmental legislative, compliance, restoration, cleanup, and DoD guidance information. It is intended to serve as a central electronic "meeting place" where information can be exchanged among environmental professionals worldwide. The DENIX library WWW site contains links to a variety of useful information and documents to assist users with air quality issues. Visit the DENIX library site at

Document References
  1. Clean Air Act, as amended (42 U.S.C. 7401 et seq.).
  2. Title 40 CFR Parts 50-87 (Regulations promulgated under the CAA).
  3. AFI 32-7040, Air Quality Compliance, 9 May 1994.
  4. The Plain English Guide To the Clean Air Act, USEPA, EPA 400-K-93-001, April 1993.
  5. Taking Toxics Out of the Air, EPA 451/K-98-001, February 1998.
  6. AF Clean Air Act Reference Guide, HQ USAF/CEV, January 1993.
  7. US Air Force Guide to Air Quality Management, HQ USAF/CEV, January 1993.
  8. US Air Force Conformity Guide, HQ USAF/CEV, August 1995.
  9. Clean Air Act Impact Interactive Training Compact Disc - V. 1.0, HQ USAF/CEV, May 1996.
  10. Interim Implementation of New Source Review Requirements for PM2.5, 23 November 1997, EPA Office of Air Quality Planning & Standards (OAQPS).
  11. National Ambient Air Quality Standards for Particulate Matter; Final Rule, 65 FR 38651, 18 July 1997
  12. National Ambient Air Quality Standards for Ozone; Final Rule, 65 FR 38855, 18 July 1997.
  13. Potential to Emit (PTE) Guidance for Specific Source Categories, EPA, 22 April 1998.
  14. Major Source Determinations for Military Installations under the Air Toxics, New Source Review, and Title V Operating Permit Programs of the Clean Air Act, John S. Seitz, Director, EPA OAQPS, 2 August 1996.