Air Pollution Control Division

NESHAP and MACT Standards
Stationary Sources Program

Are existing facilities "grandfathered"?

MACT Sources and Permitting Requirements

MACT guidance documents and links

What are NESHAPS and MACT standards?

The 1990 Clean Air Act (CAA) Amendments established a new and fairly complex program to regulate emissions of 188 hazardous air pollutants (HAPs) from particular industrial sources. The Act required the US Environmental Protection Agency (USEPA) to regulate emissions of these HAPs by developing and promulgating technology-based standards based on the best-performing similar facilities in operation. The national emission standards for hazardous air pollutants (NESHAPs) established by the U.S. Environmental Protection Agency (EPA) are commonly called maximum achievable control technology (MACT) standards. MACT standards are designed to reduce HAP emissions to a maximum achievable degree, taking into consideration the cost of reductions and other factors. After the EPA adopts a MACT standard at the federal level, the Regulatory and Compliance Support Unit proposes the same standard for adoption at the state level by the Air Quality Control Division on a semi-annual basis.

When developing a MACT standard for a particular source category, the EPA looks at the current level of emissions achieved by best-performing similar sources through clean processes, control devices, work practices, or other methods. These emissions levels set a baseline, often referred to as the "MACT floor" for the new standard. At a minimum, a MACT standard must achieve, throughout the industry, a level of emissions control that is at least equivalent to the MACT floor. The EPA can establish a more stringent standard when it makes economic, environmental, and public health sense to do so. 

The MACT floor differs for existing sources and new sources.

• For existing sources, the MACT floor must equal the average current emissions limitations achieved by the best-performing 12 percent of sources in the source category, if there are 30 or more existing sources. If there are fewer than 30 existing sources, the MACT floor must equal the average current emissions limitation achieved by the best-performing five sources in the category. 
  
• For new sources, the MACT floor must equal the current level of emissions control achieved by the best-controlled similar source. 

Wherever feasible, the EPA writes the final MACT standard as an emissions limit-a percent reduction in emissions or a concentration limit that regulated sources must achieve. Emissions limits provide flexibility for industries to determine the most effective ways to comply with the standards. 

Sources subject to MACT standards are classified as either major sources or area sources.

• Major sources are sources that emit 10 tons per year of any of the listed HAPs, or 25 tons per year of a mixture of HAPS. These sources may release HAPs from equipment leaks, when materials are transferred from one location to another, or during discharge through emission stacks or vents. 
  
• Area sources consist of smaller-size facilities that release lesser quantities of HAPs into the air. Area sources are sources that emit less than 10 tons per year of a single HAP, or less than 25 tons per year of a combination of HAPs. Though emissions from individual area sources are often relatively small, collectively their emissions can be of concern, particularly where large numbers of sources are located in heavily populated areas.  
  
  Note:  On December 9, 2005, EPA finalized permanent exemptions from the Title V operating permit program for five categories of non-major (area) sources that are subject to NESHAPs.

Has a MACT standard been developed for my industry?

Each industry is responsible for determining whether an applicable MACT standard has been developed or if one has been or is being proposed.

The Clean Air Act required the EPA to develop MACT standards for all major source categories of HAPs according to a schedule listed in the Act: standards for 40 source categories by 1992, for 25 percent of the categories by 1995, for 25 percent more by 1997, and for the remaining categories by 2000. The EPA is behind schedule in setting the standards.

Finalized MACT Standards:

MACT standards have been developed and finalized for many source categories.

• View list of current MACT standards .

Do the MACT standards apply to my facility?

To determine whether a MACT standard applies to your facility, review the list of current MACT standards .  If you are a small business owner or operator, contact the Small Business Assistance Program for additional assistance.

Are existing facilities "grandfathered"?

All NESHAP or MACT standards were promulgated after 1992. Pre-existing sources still must comply with the applicable industry standard, but under an extended deadline, as long as they have not reconstructed. An extended compliance date is listed in each MACT. In setting the standards, the EPA is allowed to distinguish between new and existing sources and to subject new or reconstructed major sources to stricter controls.
"Reconstructed" means replacement of component parts of a stationary source to the extent that the capital cost of the new components exceeds 50 percent of the capital cost to construct a comparable new source if it is technologically and economically feasible for the reconstructed source to meet the MACT standard.

MACT Sources Permitting Requirements

Any facility that is subject to a MACT standard is also subject to air permitting requirements. The Construction Permit Unit provides more information on air permits for all sources, while the  Operating Permit Unit provides more information on air permits for larger sources. 

Stationary Sources I Air Pollution Control Division

Suggestions and comments regarding the Air Quality Control Division can be forwarded to comments.apcd@state.co.us