This CAFO alleges violations of the CAA based on Marsulex's exceedence of carbon monoxide (CO) emission limits from its Permit to Install (PTI) 04-00923., Ohio State Implementation Plant (SIP) Rule OAC 3745-31-05(A)(3), and Title V permit P0088529. Marsulex violated CO Limits of 0.82 lb/hr and 3.59 tons per year at both its Sulfuric Acid Plant A and Plant B decomposition furnaces from approximately 1995 to December 2010. On May 18, 2010, Marsulex notified EPA that it had committed violations of its CO permit limits and requested consideration pursuant to EPA's Audit Policy. The circumstances of these violations do not qualify for penalty reductions under the audit policy and this action resolves these violations through an administrative settlement and a penalty payment of $112,175. These violations were primarily caused by errors in calculating emissions of CO from the furnaces in a 1995 permitting action and were subsequently prolonged by Marsulex's failure to diligently ensure compliance. Marsulex has taken several actions since May 2010 to bring these units into compliance including stack testing and permit modifications. At this time, EPA believes Marsulex is in compliance with the CO emission limitations in its revised permits.