We, the United States Environmental Protection Agency (EPA), are approving the Ohio Environmental Protection Agency's (OEPA) September 16, 1998 and December 29, 1998, requests for revisions to the Ohio State Implementation Plan (SIP). These requests include an exemption for de minimis sources from the requirement to obtain a permit to operate (OAC 3745-15-05) and revises the permit to operate rule (OAC 3745-35-02). Revisions to OAC 3745-35-02 establish exemptions from the rule, revise the application filing deadline, and allow applicants the ability to demonstrate that their sources are in compliance through a compliance schedule when they are not in compliance at the time of permit issuance. These revisions will not inhibit OEPA from ensuring compliance with the national ambient air quality standards.