H.R. 1873 is a multi-pollutant legislative proposal (or 4-P bill) that would establish national tonnage caps for nitrogen oxides, sulfur dioxide, mercury, and carbon dioxide.  In light of the caps proposed by the Act, it also proposes to streamline the federal New Source Review (NSR) permitting program.

The Act represents a middle-ground between the Clear Skies Act and the Clean Power Act.  The emission reduction targets and timelines proposed by the Clean Air Planning Act are generally earlier and in some cases more stringent than those proposed by the Clear Skies Act.  Also, the Clean Air Planning Act would limit emissions of CO2.  The Clean Power Act is generally more aggressive than the Clean Air Planning Act both in terms of timing and in terms of the reduction targets that it proposes.