This action finalizes corrections and updates to test methods and performance specifications for air emission sources under 40 CFR parts 51, 60, and 63. The revisions include corrections to testing provisions that contain inaccuracies and typographical errors, updates to outdated test methods, and the addition of alternative testing procedures to provide testers enhanced flexibility. For example, the incorrect chemical compound, sodium sulfite would be replaced with sodium nitrite in Method 7C. In Method 12, SW-846 methods would be added as alternative analytical procedures. The 2010 version of ASTM D2369 would be added to Method 24. Various sections of Performance Specification 9 are confusing and would be re-written to provide clarity. This action is developed every few years to keep rules up-to-date and to ensure that compliance testing and monitoring are done correctly.