A person who owns or operates a cement kiln at a Portland cement manufacturing plant shall meet the following applicable NOx emission standards: For long dry kilns, maximum emissions of 5.1 pounds of NOx per ton of clinker produced; and For pre-calciner kilns, maximum emissions of 2.8 pounds of NOx per ton of clinker produced. On and after April 1, 2017, the requirements in §A of this regulation no longer apply and cement kilns shall meet the applicable NOx emission standards in §C of this regulation. On and after April 1, 2017, a person who owns or operates a cement kiln at a Portland cement manufacturing plant shall meet the following applicable NOx emission standards: For long dry kilns, maximum emissions of 3.4 pounds of NOx per ton of clinker produced; and For pre-calciner kilns, maximum emissions of 2.4 pounds of NOx per ton of clinker produced. Compliance with the emission standards in §§A and C of this regulation shall be demonstrated as a 30-day rolling average.