Section 66.35 - Revocation of exemptions(a) The Administrator may upon notice and opportunity for a hearing revoke an exemption granted to the owner or operator of any source at any time in accordance with paragraphs (b) and (c) below.(b) An exemption may be revoked and a penalty for the period of non-exempted noncompliance assessed if:(1) The grounds for the exemption no longer exist or never did exist, or(2) In the case of an exemption under § 66.31 , the source owner or operator has failed to comply with any interim emission control requirements or schedules of compliance (including increments of progress) contained in the extension, order, suspension or EPA-approved consent decree on which the exemption was based.(c) The Administrator shall provide the source owner or operator written notice containing the information required by § 66.12 and a statement of the reasons for revocation. The notice shall also specify the date from which the source owner or operator must calculate a penalty. The notice shall be transmitted as required by § 66.12 . The source owner or operator shall respond to this notice within 45 days of its receipt and in the form provided in § 66.13 .