This action finalizes the residual risk and technology reviews (RTR) conducted for the Mineral Wool Production and Wool Fiberglass Manufacturing source categories regulated under national emission standards for hazardous air pollutants (NESHAP). Under this action, we are establishing pollutant-specific emissions limits for hazardous air pollutants (HAP) that were previously regulated (under a surrogate) and for HAP that were previously unregulated. This action finalizes first- time generally available control technologies (GACT) standards for gas- fired glass-melting furnaces at wool fiberglass manufacturing facilities that are area sources. We are also amending regulatory provisions related to emissions during periods of startup, shutdown, and malfunction (SSM); adding requirements for reporting of performance testing through the Electronic Reporting Tool (ERT); and making several minor clarifications and corrections. The revisions in these final rules increase the level of emissions control and environmental protection provided by the Mineral Wool Production and Wool Fiberglass Manufacturing NESHAP.