Clean Air Act (CAA) Compliance Monitoring

EPA works with its federal, state and tribal regulatory partners to monitor and ensure compliance with clean air laws and regulations in order to protect human health and the environment. The Clean Air Act is the primary federal law governing air pollution.

Compliance Monitoring Strategy

EPA’s CAA Stationary Source Compliance Monitoring Strategy (CMS) provides guidance to EPA and authorized states with respect to administering and implementing an Agency program for CAA compliance monitoring.

EPA and authorized states make decisions about compliance monitoring based on:
  • implementing an EPA or state plan, or
  • "for cause" - that is:
    • as a result of tips complaints, or
    • as a follow-up to previous monitoring activities.

Major Program Areas for Compliance Monitoring Under the Clean Air Act

EPA monitors compliance of regulated operations (facilities, activities, and entities) pursuant to CAA in several major program areas:

  • Acid Rain Inspection and Trading Program

    The goal of the program is to achieve significant environmental and public health benefits through reductions in emissions of sulfur dioxide (SO2) and nitrogen oxides (NOx), the primary causes of acid rain.  To achieve this goal at the lowest cost to society, the program employs both traditional and innovative, market-based approaches for controlling air pollution. In addition, the program encourages energy efficiency and pollution prevention.

  • Applicability Determination Index (ADI)

    The general provisions of 40 CFR Parts 60 and 61 allow a source owner or operator to:

    • request a determination of whether a rule applies to them (applicability determinations); or
    • seek permission to use monitoring or record keeping which is different from the promulgated standards (alternative monitoring).

    To ensure national consistency in implementing the NSPS and NESHAP programs, EPA maintains a compilation of such letters and memoranda since they were first issued. This compilation is currently available on the Applicability Determination Index (ADI) database Web site. The ADI also contains “regulatory interpretations” which are written responses that apply to the broad range of NSPS and NESHAP regulatory requirements as they pertain to a whole source category. The ADI is a computerized database which allows users to search by date, office of issuance, subpart, citation, control number, or keyword searches.

  • Asbestos Demolition and Renovation

    The Asbestos National Emission Standards for Hazardous Air Pollutants (NESHAP) program focuses on renovation and demolition activities and waste disposal sites. It applies to asbestos generation during mining, manufacturing/fabricating, renovation and demolition and waste disposal.

    EPA, state and local air program inspectors inspect renovation and demolition sites to determine compliance with the Asbestos National Emission Standards for Hazardous Air Pollutants (NESHAP)

  • Mobile Sources

    EPA's Clean Air Act Mobile Sources Program promulgates emissions standards for virtually all motor vehicle and non-road vehicles and equipment and the fuels that are used in them. The mobile source standards apply to vehicles and engines, ranging from huge engines that power large marine vessels and locomotives, to small engines used in hand-held lawn and garden equipment. The fuels standards apply to all gasoline and diesel fuel used nationwide, including fuel that is produced at domestic refineries and fuel that is imported.

  • National Emission Standards for Hazardous Air Pollutants (NESHAP) Air Toxics

    Section 112 of the CAA requires the EPA to establish, among other things, standards for emissions of hazardous air pollutants (HAP) for specific source categories.  These standards require the maximum degree of reduction of HAPs at the time the standard is established, commonly referred to as “maximum achievable control technology” or “MACT.” The National Emission Standards for Hazardous Air Pollutants (NESHAP) are found in 40 CFR Parts 61 and 63. The NESHAPS apply to both new and existing sources at the time that EPA establishes the standards.  This applicability is somewhat different from NSR and NSPS for existing units, which is dependent on an action in the future. 

  • New Source Review/Prevention of Significant Deterioration (NSR/PSD)

    Sections 165 and 173 of the CAA and their implementing regulations require new or modified major sources that increase regulated air pollutants by designated thresholds to meet specific permitting requirements and install Best Available Control Technology (BACT) or Lowest Achievable Emission Rate (LAER) technology. Affected sources must also demonstrate that operation will not cause or contribute to a violation of the National Ambient Air Quality Standards (NAAQS). These controls are “technology-forcing” in that the best controls keep improving, so what represents BACT/LAER today may not be BACT/LAER in the future.

  • Prevention of Accidental Releases

    Section 112(r) of the CAA also imposes a general duty on owners and operators of stationary sources producing, processing and storing extremely hazardous substances to:

    • identify hazards associated with an accidental release,
    • design and maintain a safe facility, and
    • minimize consequences of accidental releases that occur. 

    Section 112(r) requires EPA to establish regulations to prevent the accidental release of HAPs.

  • Standards of Performance for New Stationary Sources

    Section 111 of the CAA requires the EPA to develop Standards of Performance for New Stationary Sources which apply specific technology or limits to categories of stationary sources that cause or contribute significantly to air pollution. These standards are referred to as New Source Performance Standards (NSPS). The NSPS apply to new, modified, or reconstructed affected facilities in specific source categories such as manufacturers of glass, cement, rubber tires and wool fiberglass. As of 2012, EPA had developed 94 NSPS. EPA can delegate the responsibility to implement and enforce the NSPS (or a subset) to its partners (states, local, territorial, or tribal), however, even when delegated to the states, EPA retains authority to implement and enforce the NSPS.

  • Stratospheric Ozone Protection including chlorofluorocarbon (CFCs) and other Ozone-Depleting Substances (ODS)

    The CAA Section 601-618, requires EPA to develop programs that protect the stratospheric ozone layer. The stratosphere, or "good" ozone layer, extends upward from about 6 to 30 miles and protects life on Earth from the sun's harmful ultraviolet (UV) rays. This natural shield has been gradually depleted by man-made chemicals like chlorofluorocarbons (CFCs) and hydro-chlorofluorocarbons (HCFCs). A depleted ozone shield allows more UV radiation to reach the ground, leading to more cases of skin cancer, cataracts, and other health and environmental problems. EPA’s regulatory programs that protect the ozone layer include:

    • phase-out of the production and import of ozone-depleting substances,
    • requirements for the service and disposal of stationary refrigeration and air-conditioning,
    • service of motor vehicle air-conditioning, and  
    • labeling of products containing or manufactured with ozone depleting substances.  

    See Ozone Layer Protection

  • Wood Heaters

    Residential wood heaters, which include wood stoves, contribute significantly to particulate air pollution. EPA has regulated wood heater particulate emissions since 1988. Wood heater model lines that are in compliance with the rule are referred to as EPA-certified wood heaters.

    EPA's certification process requires manufacturers to verify that each of their wood heater model lines meet a specific particulate emission limit by undergoing emission testing at an EPA accredited laboratory.

Stack Testing

Beyond the CAA CMS, the CAA National Stack Testing Guidance provides additional guidance on implementing stack testing, one of the most important tools for determining whether a facility has the ability to comply with the CAA. The Stack Testing Guidance addresses legal and policy issues associated with the conduct of stack tests and the interpretation of test results.

Risk Management Plan

The Risk Management Plan Rule (RMP Rule) provides guidance for chemical accident prevention at facilities using extremely hazardous substances. The rule, which built upon existing industry codes and standards, requires companies of all sizes that use certain flammable and toxic substances to develop a Risk Management Program.

A summary of the facility's Risk Management Program must be submitted to EPA and must be revised and resubmitted every five years. The Guidance for Conducting Risk Management Program Inspections under Clean Air Act Section 112(r) provides information on conducting on-site compliance evaluations at RMP facilities.

Area Source Rule

The Area Source Rule Implementation Guidance provides guidance regarding the implementation of the CAA Area Source Rules.