Progress Report

Emission Controls and Monitoring

Many sources opted to install control technologies to meet the Acid Rain Program (ARP) and Cross-State Air Pollution Rule (CSAPR) emission reduction targets.1 A wide range of controls is available to help reduce emissions. Affected units under the Mercury and Air Toxics Standards (MATS) also have several options for reducing hazardous air pollutants and have some flexibility in how they monitor emissions. These programs hold sources to high standards of accountability for emissions. Accurate and consistent emissions monitoring data are critical to ensure program results and accountability. Most emissions from affected sources are measured by continuous emission monitoring systems (CEMS).


  1. CSAPR refers to the CSAPR, the CSAPR Update, and the Revised CSAPR Update programs.

Emission Controls and Monitoring Figures

SO₂ Controls
SO₂ Emissions Controls in the ARP and CSAPR SO₂ Program, 2021
CSAPR SO₂ Program Monitoring Methodology
CSAPR SO₂ Program Monitoring Methodology, 2021
NOₓ Annual Program Controls
NOₓ Emissions Controls in CSAPR NOₓ Annual Program, 2021
CSAPR NOₓ Annual Program Monitoring Methodology
CSAPR NOₓ Annual Program Monitoring Methodology, 2021
NOₓ Ozone Season Controls
NOₓ Emissions Controls in CSAPR NOₓ Ozone Season Program, 2021
CSAPR NOₓ Ozone Season Program Monitoring Methodology
CSAPR NOₓ Ozone Season Program Monitoring Methodology, 2021
Mercury Controls at MATS-Affected Sources
Mercury Controls at MATS-Affected Sources, 2021
Mercury Compliance and Monitoring Methods
Mercury Compliance and Monitoring Methods used by Units Reporting Hourly Data under MATS, 2021