[Code of Federal Regulations] [Title 40, Volume 5] [Revised as of July 1, 2003] From the U.S. Government Printing Office via GPO Access [CITE: 40CFR57.401] [Page 143] TITLE 40--PROTECTION OF ENVIRONMENT CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) PART 57--PRIMARY NONFERROUS SMELTER ORDERS--Table of Contents Subpart D--Supplementary Control System Requirements Sec. 57.401 General requirements. Except as provided in subpart E, each NSO shall require the smelter owner to prevent all violations of the NAAQS in the smelter's designated liability area (DLA) through the operation of an approved supplementary control system (SCS).