MATS (Mercury and Air Toxic Standards) Overview Information

MATS - Mercury and Air Toxics StandardsEPA - Environmental Protection Agency

MACT - Maximum Achievable Control TechnologyNESHAP - National Emission Standards for Hazardous Air Pollutants

EGUs - Electric Generating Units

The Mercury and Air Toxics Standards provide regulatory certainty for power plants. Additionally, these standards level the playing field so that all plants will have to limit their emissions of mercury as newer plants already do.

Use of widely-available controls will reduce harmful air toxics and help modernize the aging fleet of power plants, many of which are over 50 years old.

The MATS sets standards for all Hazardous Air Pollutants (HAPs) emitted by coal- and oil-fired EGUs with a capacity of 25 megawatts or greater. These are called national emission standards for hazardous air pollutants (NESHAP), also known as maximum achievable control technology (MACT) standards. Coal- and/or oil-fired electric utilities emit many of the 187 hazardous air pollutants listed in the Clean Air Act.

Emission standards set under the toxics program are federal air pollution limits that individual facilities must meet by a set date. MACT for new sources must be at least as stringent as the emission reduction achieved by the best performing similar source.  Existing source MACT standards must be at least as stringent as the emission reductions achieved by the average of the top 12 percent best controlled sources.  These standards must address all hazardous air pollutants emitted at a source category.

Source – EPA & National Emission Standards for Hazardous Air Pollutants from Coal- and Oil-fired Electric Utility Steam Generating Units and Standards of Performance for Fossil-Fuel-Fired Electric Utility, Industrial-Commercial-Institutional, and Small Industrial- Commercial-Institutional Steam Generating Units.

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New sources must conduct their first biennial or 5-year tune-up no later than 25 months or 61 months, respectively, after start-up, and must prepare a Compliance Certification Report biennially or every 5 years, as applicable, by March 1 of the year following the tune-up. (

EGU’s equal to or greater than 10 MMbtu/hr requires a Tune-up required every 2 years (units with continuous oxygen trim system – tune-up every 5 years) – serves as work practice standard for dioxin/furan emissions.

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