On March 16, 2015, EPA published a final rule that made revisions to the New Source Performance Standards (NSPS) for new residential wood heaters (80 FR 13672). The 2015 final rule updated the 1988 NSPS to reflect significant advancements in wood heater technologies and design, broadened the range of residential wood-heating appliances covered by the regulation, and improved and streamlined implementation procedures. The 2015 rule requires manufacturers to redesign wood heaters to be cleaner and lower emitting. In general, the design changes also make the heaters perform better and more efficiently. On November 30, 2018, EPA published a Notice of Proposed Rulemaking (NPRM) to amend the 2015 rule, requesting comment on whether the minimum pellet fuel requirements should be retained and, if so, whether they should be revised (83 FR 61574). Also on November 30, 2018, EPA published an Advance Notice of Proposed Rulemaking (ANPRM) to solicit comment on several aspects of the 2015 final rule, including: the compliance date for the Step 2 PM limits (while part of the ANPRM, the compliance date will not be part of the proposal); Step 2 PM limits for forced-air furnaces, hydronic heaters, and wood stoves; Step 2 PM limits based on weighted averages versus individual burn rates; transitioning to cord wood certification test methods; compliance audit testing; third-party review; electronic reporting; and warranty requirements (83 FR 61585). On April 2, 2020, EPA finalized the rule that was proposed on November 30, 2018 (FR 85 18448). The final rule addressed minimum pellet requirements and other issues identified in the proposed rule. Regulatory development for the next iteration of the NSPS will proceed once the new emission test methods have been promulgated for wood heaters. The new test methods will yield the relevant data required to determine whether the standards of performance should be updated. The target dates for promulgation of the new test methods are currently projected for summer 2025 to summer 2026. On September 21, 2023, EPA received a complaint from ten Attorneys General and a local air agency regarding EPA’s failure to perform its 8-year review of the residential wood heaters NSPS (subparts AAA and QQQQ). A Federal Register notice announcing a proposed consent decree establishing deadlines for EPA to conduct their review was published on July 26, 2024 (89 FR 60629). A final consent decree was entered with the court that established a proposal date of December 15, 2026 for subpart AAA and a promulgation date of December 15, 2027. For QQQQ, a proposal date of December 15, 2027 and a promulgation date of December 15, 2028 were agreed to for completion of review.