Skip to main content

National Emission Standards for Hazardous Air Pollutants

The Clean Air Act requires the U.S. EPA to regulate emissions of air pollutants that are hazardous to human health or the environment, called hazardous air pollutants (HAPs). The regulations are known as National Emission Standards for Hazardous Air Pollutants (NESHAP).

There are two types of facilities covered by NESHAPs:

  • Major sources have the potential to emit more than 10 tons per year of a single HAP or 25 tons per year of any combination of HAPs.
  • Area sources have the potential to emit less than 10 tons per year of a single HAP or 25 tons per year of any combination of HAPs. Many small businesses are area sources.

NESHAPs are an additional federal standard beyond an air permit, so whether or not your business has an air permit, you may still need to meet the requirements of a NESHAP. Due to the number and variety of NESHAPs, it is likely that at least one applies to your business. Review the list of NESHAPs on the EPA web site.

New Source Performance Standards

New Source Performance Standards (NSPS) are similar to NESHAPs, but require testing to confirm compliance. Boilers, engines and generators, grain elevators, hot-mix asphalt plants, and perc dry cleaners all have NSPS. Review the list of NSPS on the EPA web site.

Contact the Small Business Assistance Program (651-282-6143, 800-657-3938) for help determining if a NESHAP or NSPS applies to your business.


Area source NESHAPs are a group of standards that require area sources to follow generally available control technologies (GACT) standards.

Criteria pollutants are seven pollutants determined by the U.S. EPA to be hazardous to human health. The term "criteria pollutants" comes from the requirement that the EPA describe the pollutants' characteristics and potential health and welfare effects. Air quality standards are established based on these criteria.

  • carbon monoxide
  • lead
  • nitrogen oxide
  • ozone
  • particulate matter with diameters of 10 micrometers or less (PM 10)
  • particulate matter with diameters of 2.5 micrometers or less (PM 2.5)
  • sulfur dioxide

Major source NESHAPs are a group of standards that apply to emission units at major sources, and require them to follow maximum achievable control technologies (MACT) standards.

New source review is a federal requirement for new and expanding major source facilities and for minor source facilities where the expansion would be a major source on its own. For new source review, a major source has potential emissions of criteria and other pollutants of more than 100 tons/year or over 250 tons/year, depending on industry type. New source review requires facilities to get permits before construction starts; it does not generally affect existing facilities that can stay within the limits of their registration permit.

“Once in always in” was an EPA policy issued in 1995 and withdrawn in January 2018. Under the policy, once a source was subject to a major source NESHAP, it would always be subject to the standard, regardless of the source's air emissions. Now that the policy is withdrawn, major sources can be reclassified as area sources if they qualify.

Potential to emit (PTE) is the maximum amount of pollutants that a facility could possibly emit in a year, if it were operating 24/7. PTE calculations are used to determine if a facility needs an air permit or must comply with federal standards, and if so, which ones.

Prevention of significant deterioration is how new source review is implemented in areas that are in attainment with National Ambient Air Quality Standards. Most of Minnesota is in attainment; part of Dakota County is the exception, due to lead.

Volatile organic compounds (VOCs) are any organic compounds that participate in smog-forming reactions, except for those designated by the EPA Administrator as having negligible photochemical reactivity. A list of exempted volatile organic compounds is available in Minnesota Rule 7005.0100.