This proposal presents the results of the U.S. Environmental Protection Agency's (EPA) residual risk and technology review for the National Emission Standards for Hazardous Air Pollutants (NESHAP) from Hazardous Waste Combustors (HWC) as required under the Clean Air Act (CAA). In this action, the EPA is proposing to establish emission limits and work practice standards for hydrogen fluoride and hydrogen cyanide emissions from HWC incinerators, cement kilns, solid fuel boilers, and liquid fuel boilers; eliminate the startup, shutdown, and malfunction (SSM) exemption; add a work practice standard for periods of SSM; add electronic reporting procedures and requirements; allow states to choose to exempt area sources from certain permitting requirements; and other clarifications and corrections. In response to comments received on certain aspects of the July 24, 2024, proposed revisions for periods of malfunction, the EPA is withdrawing that proposed rule and instead proposing different provisions to address periods of SSM. Comments must be received on or before 26 December 2025. POC is Rachel Smoak, tele: (919) 541-0253; and email: smoak.rachel@epa.gov. (Federal Register 10 November 2025 [Proposed Rule] Pages 50814-50855)