EPA is issuing amendments to the national emission standards for hazardous air pollutants (NESHAP) for semiconductor manufacturing. These amendments establish a new maximum achievable control technology floor level of control for existing and new combined hazardous air pollutants process vent streams containing inorganic and organic hazardous air pollutants and clarify the emission requirements for process vents by adding definitions for organic, inorganic, and combined hazardous air pollutant process vent streams that contain both organic and inorganic hazardous air pollutant.