EPA signed a final rule February 21, 2011, that establishes national emissions standards for hazardous air pollutants (NESHAPs) for existing and new industrial, commercial and institutional boilers. According to EPA, because the final rule differs significantly from the proposed rule, the agency will reconsider the final standards under a Clean Air Act process that allows the agency to seek additional public review and comment.

The rule sets numeric emissions limits for mercury, dioxins, particulate matter, hydrogen chloride, and carbon monoxide for 15 different subcategories of major source boilers and process heaters. It requires the largest boilers and process heaters to continuously monitor particulate matter emissions as a surrogate for toxic metals, such as lead and chromium, as well as monitor oxygen to ensure clean combustion. EPA will release additional details on its reconsideration process at a later date. In a separate action, EPA will also issue a rule to reduce air toxics from commercial and industrial solid waste incinerators and sewage sludge incinerators. The final boiler rule will be effective 60 days after publication in the Federal Register.