This action finalizes the periodic review by the U.S. Environmental Protection Agency (EPA) of the emissions standards and other requirements for Other Solid Waste Incineration (OSWI) units in the OSWI New Source Performance Standards (NSPS) and Emission Guidelines (EG). The EPA is finalizing applicability-related and definitional changes; changes to OSWI subcategories and the standards for the new subcategories; changes to the startup, shutdown, and malfunction (SSM) provisions; and changes to testing, monitoring, recordkeeping, and reporting requirements. We are also making other miscellaneous technical and editorial changes to the regulatory text. This final rule is effective 29 August 2025. POC is Felica Davis, Ph.D.; tele: (919) 541-4857; and email: davis.felica@epa.gov. (Federal Register 30 June 2025 [Rule] Pages 27910-27971)