The U.S. Environmental Protection Agency (EPA) is promulgating revisions to new source performance standards (NSPS) for residential wood stoves, and promulgating NSPS for other wood heating appliances such as pellet stoves, forced air furnaces, single burn rate stoves, and hydronic heaters. The EPA is submitting 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. We are amending 40 CFR part 60, subpart AAA, Standards of Performance for New Residential Wood Heaters. The current regulation (subpart AAA) applies to affected residential wood stoves manufactured since 1988. Except as discussed in this final rule, the current requirements would remain in effect for the heaters/stoves and model lines manufactured before this action. In this final rule, we also are broadening the applicability of the wood heaters regulation beyond adjustable burn rate heaters (i.e., “stoves�, the focus of the original regulation) to specifically include single burn rate heaters, pellet stoves, hydronic heaters, and forced-air furnaces. Heaters/stoves and model lines manufactured after the compliance dates would be required to meet fine particulate matter (PM2.5) standards. Compliance upon the effective date of the final rule is the intention in section 111 of the CAA. Revision of the current residential wood heaters NSPS is necessary to capture the improvements in performance of such units and to include additional wood-burning residential heating devices. The revisions are expected to achieve several objectives, including the application of updated emission limits reflecting the best emission reduction systems; elimination of exemptions over a broad suite of residential wood combustion devices; the strengthening of test methods as appropriate; and the streamlining of the certification process. The EPA proposed NSPS for new residential masonry heaters; however, we are not taking final action on these wood combustion devices at this time in order to allow additional time for the Masonry Heater Association (MHA) to finish their efforts to develop revised test methods and alternative compliance calculation procedures. This final rule does not include any requirements for heaters solely fired by gas, oil or coal. In addition, it does not include any requirements associated with wood heaters or other wood-burning appliances that are already in use. The EPA continues to encourage state, local, tribal, and consumer efforts to change out (replace) older heaters with newer, cleaner, more efficient heaters, but that is not part of this Federal rulemaking. These revisions help address the health impacts of particle pollution, of which wood