Boilers (Steam Generating Units) are commonly used as a source of energy on farms. There are two types of air emission regulations for boilers.

• New Source Performance Standards for Boilers limit sulfur dioxide, particulate matter, and nitrous oxides emissions from boilers built after certain dates.
• National Emission Standards for Hazardous Air Pollutants for Industrial, Commercial, and Institutional Boilers reduce toxic air pollutant emissions, including mercury and particle pollution.