(a) Portland cement kilns exempted from the provisions of this division (relating to Cement Kilns), include any portland cement kiln placed into service on or after December 31, 1999, except as specified in §§117.3110, 117.3120, 117.3123, and 117.3124 of this title (relating to Emission Specifications; Source Cap; Dallas-Fort Worth Eight-Hour Ozone Attainment Demonstration Control Requirements; and Bexar County Control Requirements for Reasonably Available Control Technology (RACT)).(b) Any account in Ellis County with no portland cement kilns in operation prior to January 1, 2001, is exempt from §117.3123 of this title.(c) After the compliance date specified in §117.9320(c) of this title (relating to Compliance Schedule for Cement Kilns), portland cement kilns that are subject to §117.3123 of this title are exempt from §117.3110 and §117.3120 of this title between March 1 and October 31 of each calendar year.(d) After the compliance date specified in §117.9320(c) of this title, portland cement kilns that are subject to §117.3124 of this title are exempt from §117.3110 and §117.3120 of this title.