On Thursday, August 16, 2012, the EPA promulgated affirmative defense provisions as part of the Risk and Technology Review of subparts HH and HHH of part 63 Standards for Hazardous Air Pollutants at 77 FR 49490. The D.C. Circuit Court issued an opinion vacating the portion of EPA’s Portland Cement Manufacturing Industry NESHAP that established an affirmative defense for emissions violations caused by “unavoidable” malfunctions (NRDC v. EPA, 749 F.3d 1055 (D.C. Cir. 2014). The purpose of this proposal is to address the affirmative defense provision in subpart HH/HHH in light of the NRDC decision.