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Please note: This summary is provided to help you understand the regulations. Consult the references provided for links to the full text of the regulations.


Road Rail Air Water

This section covers air pollution regulations associated with a group of combustion units that fall into the regulatory category "industrial/commercial/institutional (ICI) boilers." Within this group are commercial boilers that are used by wholesale and retail trade, office buildings, light industry, and airports to supply steam and hot water for space and water heating. Commercial boilers generally have heat input capacities below 10 MMBtu/hr, but some are significantly larger.

Other environmental regulations that may apply to boiler operation include rules covering solid/hazardous waste; water resources protection; and spill prevention, control and counter measures.

Who is covered by the regulations?

Facilities with ICI boilers rated above 10 MMBtu/hr (2.9 megawatts) are covered by federal air pollution regulations termed New Source Performance Standards (NSPS). Smaller units are not covered by federal regulations, but state rules may apply to them. The NSPS are applicable to boilers constructed, modified, or reconstructed after 9 June 1989. In addition to NSPS, in the future some facilities may be subject to newly proposed rules termed National Emissions Standards for Hazardous Air Pollutants (NESHAPs). States may regulate boilers differently from the Federal EPA, including rules that are more encompassing (e.g. covering boilers smaller than 10 MMBtu/hr) or that have more stringent emission standards.

What is the purpose of the regulations?

ICI boilers emit pollutants such as hazardous air pollutants (HAPs), particle pollution, and volatile organic compounds (VOC). These pollutants can contribute to health problems that may affect employees, residents, and the community. While Federal, state, local, and Tribal regulations limit the amount of emissions from ICI boilers, dangerous releases of HAPs can occur if an ICI boiler does not operate in compliance with regulations.

Boilers that burn solid fuels may generate residuals such as coal ash. Regulations covering fuel and waste storage are in place to assure that these materials are not released to the environment.

Air Pollution Regulations

The following is a summary of Federal air pollution regulations that impact boilers. An in-depth discussion of environmental regulations affecting ICI boilers can be found on the Combustion Portal. This web portal was developed under the National Compliance Assistance Centers program. It covers air pollution; solid/hazardous waste; water resources protection; spill prevention, control and counter measures; and pollution prevention and it maintains a list of useful ICI boiler compliance assistance resources.

New Source Performance Standards (NSPS). Section 111 of the Clean Air Act requires EPA to establish Standards of Performance for New Stationary Sources for emissions of air pollutants from facilities which cause or contribute significantly to air pollution. These standards are intended to promote use of the best air pollution control technologies, taking into account the cost of such technology and any other non-air quality, health, and environmental impact and energy requirements. These standards apply to sources which have been constructed or modified since the proposal of the standard. Since December 23, 1971, EPA has promulgated 88 such standards and associated test methods.

Generally, state and local air pollution control agencies are responsible for implementation, compliance assistance, and enforcement of the New Source Performance Standards. EPA retains concurrent enforcement authority and is also available to provide technical assistance when a state or local agency seeks help. EPA also retains a few of the NSPS responsibilities, such as the ability to approve alternative monitoring methods, to maintain a minimum level of national consistency.

New Source Performance Standards for ICI boilers were established in the mid-1980s. The applicability of the standards is determined by the age of the unit and its rated capacity:

  • Standards for small boilers are applicable to units with a heat input capacity between 10 - 100 MMBtu/hr that were constructed, modified, or reconstructed after June 9, 1989, and
  • Standards for large boilers are applicable to units with a heat input capacity in excess of 100 MMBtu/hour that were constructed, modified, or reconstructed after June 19, 1984.

Depending on the size of the unit and type of fuel combusted, the regulations include emission standards for sulfur dioxide (SO2), nitrogen's oxides (NOx) and particulate matter (PM). The NSPS also have requirements for monitoring and record keeping. More information on the ICI boiler NSPS.

National Emissions Standards for Hazardous Air Pollutants (NESHAPs). NESHAPs are emissions standards set by U.S. EPA for an air pollutant not covered by National Ambient Air Quality Standards (NAAQS) that may cause an increase in fatalities or in serious, irreversible, or incapacitating illness. The standards for a particular source category require the maximum degree of emission reduction that the EPA determines to be achievable, which is known as the Maximum Achievable Control Technology (MACT). These standards are authorized by Section 112 of the Clean Air Act and the regulations are published in 40 CFR Parts 61 and 63.

On July 21, 2022, the U.S. Environmental Protection Agency (EPA) finalized amendments to the National Emission Standards for Hazardous Air Pollutants (NESHAP) for Major Sources: Industrial, Commercial, and Institutional Boilers and Process Heaters, commonly known as the "Boiler MACT." These amendments replace the 2013 NESHAP, portions of which were remanded by courts.

EPA published a fact sheet explaining how the new limits satisfy previous courts remands.


Other Regulations

The following summarizes additional environmental regulations that should be investigated for facilities operating boilers. Additional details are available on the Center's ICI Boiler page.

  • Asbestos National Emission Standard for Hazardous Air Pollutants (NESHAP). Older boiler and steam pipe insulation commonly contain asbestos. The inhalation of asbestos fibers can cause serious diseases of the lungs and other organs that may not appear until years after the exposure has occurred. Any facility that contains asbestos is subject to the Asbestos National Emission Standard for Hazardous Air Pollutants (NESHAP). The NESHAP requires advanced notification (using an Intent to Renovate/Demolish Form) for projects exceeding established thresholds (based on linear or square feet of area disturbed) to ensure all precautions are being taken to minimize asbestos emissions. EPA has delegated the authority to enforce the asbestos NESHAP to the state environmental and/or labor agency. Find information for your state on the Asbestos State Resource Locator.

  • Solid/Hazardous Waste. Boilers that use coal as a fuel generate combustion residuals, mainly coal ash (includes both fly ash and bottom ash). They are captured by pollution control technologies, like scrubbers or removed from combustion chambers. Coal ash is currently considered an exempt waste under an amendment to the Resource Conservation and Recovery Act (RCRA). [Note that states may regulate coal ash more stringently]. However, there are environmental concerns with coal ash that pertain to pollution from impoundment and landfills leaching into ground water and structural failures of impoundments. On June 21, 2010 EPA proposed to regulate for the first time coal ash to address the risks from the disposal of the wastes. EPA is considering two possible options for the management of coal ash. The Agency considers each proposal to have its advantages and disadvantages, and includes benefits which should be considered in the public comment period.

  • Water Resources Protection. Combustion processes may generate wastewater associated with blowdown, condensate, and washout. Discharges of wastewater are regulated under the Clean Water Act (CWA). Facilities which discharge indirectly through a Publically Owned Treatment Works (POTW) are regulated under the Pretreatment Program, which insures that industrial facilities pretreat wastewater to remove pollutants which would affect the pollutant removal ability of the POTW. Facilities that discharge process or non-process wastewater directly to streams, rivers, etc. are regulated under the National Permit Discharge Elimination System (NPDES) and must obtain coverage under a General Permit or an Individual Permit.

  • Spill Prevention, Control and Counter Measures. EPA promulgated the Spill Prevention, Control and Counter Measures (SPCC) rule to reduce the risk of damaging our waterways from oil spills. An SPCC Plan is required for facilities which due to their location, could reasonably be expected to discharge oil to surface water or adjoining shorelines and have total aboveground storage capacity of 1,320 gallons or more of oil. For more information see TERC's SPCC section.

More Resources

Various programs and resources exist that are aimed at reducing the quantity of pollution, including greenhouse gas emissions (GHG), generated by operation of ICI boilers. Summaries are provided below with links to websites or full text documents.