The U.S. Environmental Protection Agency (EPA) is proposing to revise new source performance standards (NSPS) for residential wood stoves, and to issue NSPS for pellet stoves, furnaces, hydronic heaters, and masonry heaters. The EPA is proposing this revision under the authority of section 111 of the Clean Air Act (CAA), "Standards of Performance for New Stationary Sources," under which the EPA establishes federal standards of performance for new sources within source categories which cause or contribute significantly to air pollution, which may reasonably be anticipated to endanger public health or welfare.