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Clean Air Act

The Clean Air Act (CAA) is the comprehensive Federal law that regulates air emissions from area, stationary, and mobile sources. This page provides some background information on what the law covers, and indicates how it affects metal finishing facilities.

Background information on the CAA
The federal Clean Air Act (CAA) and its amendments are designed to "protect and enhance the nations air resources so as to promote the public health and welfare and the productive capacity of the population." The CAA consists of six sections, known as Titles, which direct EPA to establish National Ambient Air Quality Standards (NAAQS), and for EPA and states to implement, maintain, and enforce these standards through a variety of mechanisms. It includes programs to address smog, acid rain, stratospheric ozone protection, and air toxics. Most of the sections applicable to metal facilities are found in Titles I and V.

Note that while the federal law establishes the basic standards, it is generally up to state and local governments to manage and enforce many of its requirements.

Title I
Criteria pollutants. Pursuant to Title I of the CAA, EPA has established national ambient air quality standards (NAAQSs) to limit levels of "criteria pollutants," including:

  • carbon monoxide
  • lead
  • nitrogen dioxide
  • particulate matter
  • ozone
  • sulfur dioxide

Geographic areas that meet NAAQSs for a given pollutant are designated as "attainment areas"; those that do not meet NAAQSs are designated as "nonattainment areas". EPA provides an on-line resource called the Green Book that will allow you to determine the status of your area for each pollutant.

Under Section 110 and other provisions of the CAA, each state must develop a State Implementation Plan (SIP) to:

  • identify sources of air pollution, and
  • determine what reductions are required to meet federal air quality standards

Revised NAAQSs for particulates and ozone became effective in 2004. This may significantly affect facilities that are large sources of particulates (soot) and of volatile organic compounds or nitrogen oxides (which contribute to ozone formation), particularly those in nonattainment areas.

New sources. Title I also authorizes EPA to establish New Source Performance Standards (NSPS). These are nationally uniform emission standards for new and modified stationary sources that fall within particular industrial categories. The standards are based on the pollution control technology available to that category of industrial source (see 40 CFR Part 60).

Hazardous Air Pollutants. Also under Title I, EPA establishes and enforces National Emission Standards for Hazardous Air Pollutants (NESHAPs). These are nationally uniform standards oriented toward controlling materials that appear on a specific list. Such materials are collectively known as hazardous air pollutants (HAPs).

Section 112(c) of the CAA directs EPA to develop a list of source categories that emit any of 188 HAPs, and to develop regulations for these categories of sources. To date, EPA has listed 185 source categories, and has developed a schedule for establishing emission standards. The emission standards are being developed for both new and existing sources.

NESHAPs are based on so-called "maximum achievable control technology" (MACT). The MACT for a particular source category is defined as the control technology achieving the "maximum degree of reduction" in the emission of the HAPs when cost and other factors are taken into account. Other designations (such as "BACT", or best available control technology, and "LAER" or lowest achievable emissions reduction) are used to specify technologies satisfying other criteria, like the maximum reduction without regard to cost. The distinctions can get complicated. The important point here is that cost is factored into MACT determinations. The regulations dont specify which technology to use, but they do require that whatever technology is used must achieve at least as much of an emissions reduction as the MACT can provide.

Title V
What is Title V? Title V of the Federal Clean Air Act Amendments of 1990 (CAA) required development of permit programs which would require major sources of air emissions throughout the U.S. to obtain an operating permit. These operating permits are often referred to as "Title V Permits," or "Part 70 permits" since EPA issued rules for State Title V Programs under 40 CFR, Part 70.

AM I A TITLE V SOURCE? In general, a Part 70 permit is required of those facilities with the Potential To Emit (PTE) of 100 TPY or more of any criteria pollutant (NOx, CO, SO2, Ozone, VOCs, PM10, and Lead), or 10 TPY or more of any one Hazardous Air Pollutant (HAP), or 25 TPY or more of any combination of HAPs. Certain other sources, i.e., any affected source subject to the Acid Rain Rules, and any solid waste incinerator subject to Section 129(e) of the CAA, are required to obtain a Part 70 permit regardless of their PTE. In addition, sources subject to a New Source Performance Standard (NSPS) or a National Emissions Standard for a Hazardous Air Pollutant (NESHAP), may be specifically required by the NSPS or NESHAP to obtain a Part 70 permit.

Facilities in the metals industry have the PTE several criteria pollutants and HAPs. An emissions inventory should be performed at your facility to determine if you exceed any of the Title V thresholds. If prior to the facilitys Title V application submittal deadline a facility has applied for a minor permit which would limit emissions below the threshold levels mentioned above (i.e., by requiring operational constraints and/or control equipment), a Part 70 permit would not be required. Otherwise, PTE is calculated as if no air pollution control equipment is in place and all operations are continuous.

Applicable NESHAPs
The following is a list of the NESHAPs most applicable to metal finishing facilities. The referenced web pages contain links to the original rules and any amendments.



Surface Coating/Painting



The information contained in this site is provided for your review and convenience. It is not intended to provide legal advice with respect to any federal, state, or local regulation.
You should consult with legal counsel and appropriate authorities before interpreting any regulations or undertaking any specific course of action.

Please note that many of the regulatory discussions on STERC refer to federal regulations. In many cases, states or local governments have promulgated relevant rules and standards
that are different and/or more stringent than the federal regulations. Therefore, to assure full compliance, you should investigate and comply with all applicable federal, state and local regulations.