|
|
Regulation 9 Rule 4: Nitrogen Oxides from Natural Gas-Fired Furnaces - 2023 Amendment (Current)
Learn about the Air District's rule amendment process seeking to reduce emissions of nitrogen oxides from residential and commercial furnaces in buildings in the Bay Area through changes to Regulation 9, Rule 4.
Find out about the status and anticipated timeline of the rule development process. Information on hearings, workshops, and other events is provided below, along with supporting documents and materials.
On October 24, 2025, the Air District released a Concepts Paper for potential amendments to Rule 9-6. These changes are focused on affordability and availability considerations. They are intended to provide additional flexibility and ensure a smooth transition as older appliances are replaced with cleaner options.
- A link to the concepts paper can be found here.
The 30-day public comment period is open until November 24, 2025. Please submit written comments to ruledevelopment@baaqmd.gov.
For more information visit the Building Appliances webpage.
On October 23, 2025, the Air District hosted a virtual kick-off meeting for Phase 2 of the Implementation Working Group (IWG). The meeting focused on topics related to furnaces subject to Rule 9-4. This IWG served as an introductory meeting to review the charter, structure, and timeline. For a meeting recording please refer to the 'Hearings, Workshops and Other Events' section below.
To receive information on updates and events associated with the implementation of the amendments to Rule 9-4 and Rule 9-6, please sign up for the Air District's Building Appliances Email List:
Rule Development History
In 2023, Air District staff developed amendments to Rules 9-4: Nitrogen Oxides from Fan Type Residential Central Furnaces and 9-6: Nitrogen Oxides Emissions from Natural Gas-Fired Boilers and Water Heaters. These rules govern point of sale emission standards for small, typically residential and commercial, water and space heating systems. Emissions of nitrogen oxides impact local and regional air quality and contribute to the formation of ozone and secondary particulate matter.
Amendments to Regulation 9: Inorganic Gaseous Pollutants, Rule 4: Nitrogen Oxides from Fan Type Central Furnaces (Rule 9-4) were adopted by the Air District Board of Directors at a public hearing on March 15, 2023, along with amendments to Rule 9-6.
-Regulation 9: Inorganic Gaseous Pollutants, Rule 4: Nitrogen Oxides From Natural Gas-Fired Furnaces (Amendments Adopted 3/15/2023)
-Final Staff Report for Proposed Amendments to Rule 9-4 and Rule 9-6
Implementation Working Group
Additional Background: As part of the recent amendments, the Air District committed to convene the Implementation Working Group (IWG). The IWG for Phase 1 (water heaters) and Phase 2 (furnaces) are composed of over 40 invited stakeholders representing a variety of stakeholder segments.
The purpose of the IWG is to provide input to Air District staff’s periodic reports to the Board of Directors on the implementation of the Building Appliances Rules and to provide the Air District staff with insights on the technical readiness of the market and equitable transition to compliant appliances, so as to not unduly burden any income class or professional group. As such, the IWG provides a forum for invited members to discuss technical and equity aspects of implementing the Building Appliances Rules.
The IWG meetings for Phase 1 took place virtually via Zoom in 2023 and 2024. The IWG meeting for Phase 2 began in October 2025 and will also take place virtually via Zoom. Members of the public are able to attend in listen-only mode with the opportunity to provide public comments at the end of the meeting. Additional Information can be found on the Implementation Working Group webpage.
Adoption of Amendments to Rule 9-4 and Rule 9-6
The Air District hosted a public workshop on October 7, 2021 to discuss initial outcomes from the Building Appliance Stakeholder Working Group and first draft language of regulatory amendments. Staff provided updates to the Stationary Source and Climate Impacts Committee through 2021 and 2022. In May of 2022, the Air District released a Notice of Preparation (NOP) of an Environmental Impact Report (EIR) and an Initial Study, as well as revised draft rule amendments.
The Air District released a Notice of Public Hearing, California Environmental Quality Act (CEQA) Notice of Availability, CEQA Draft EIR, proposed amendments to Rules 9-4 and 9-6, Staff Report, and other supporting materials in December 2022 and accepted written public comments on these materials. The Air District released the Final Proposal Package, including the proposed amendments to Rules 9-4 and 9-6, Final Staff Report, CEQA Final EIR, and Response to Comments.
- Frequently Asked Questions – Adopted Amendments to Rules 9-4 and 9-6
- Fact Sheet – Proposed Amendments to Rules 9-4 and 9-6
- Infographics – Proposed Amendments to Rules 9-4 and 9-6
- Notice of Public Hearing and Notice of Availability of DEIR
- Final Environmental Impact Report for Proposed Amendments to Rule 9-4 and Rule 9-6
- Staff Report – Proposed Amendments to Building Appliance Rules – Regulation 9, Rule 4 and Rule 6
- Appendix A: Proposed Amendments to Rule 9-4
- Appendix B: Proposed Amendments to Rule 9-6
- Appendix C: Socioeconomic Impacts Analysis
- Appendix D: Electric Infrastructure Impacts from Proposed Zero NOx Standards
- Appendix E: Assessing Ambient Air Quality and Health Impacts from Natural Gas Building Appliances in the Bay Area
- Appendix F: Exposure and Equity Assessment of Natural Gas Appliances in the San Francisco Bay Area
- Appendix G: Draft Environmental Impact Report
- Appendix H: Response to Comments
The Air District Board of Directors conducted a public hearing on March 15, 2023 and adopted the proposed amendments to Rules 9-4 and 9-6 and certified the CEQA EIR. Information and a recording of the public hearing can be found on this page under 'Hearings, Workshops and Other Events'.
Rule 9-6 Implementation Report
Air District staff presented an informational update on implementation readiness of the zero NOx requirements for residential water heaters (Rule 9-6) to the Air District Board of Directors on December 4, 2024. The Board materials included a staff report summarizing information gathered during the implementation working group process, which can be found here: Staff Report - Informational Update Regarding Regulation 9, Rule 6. Appendices to the staff report can be found on the Implementation Working Group webpage.
(Archived) Submission of Rule 9-4 and Rule 9-6 to the State Implementation Plan
The Board of Directors of the Bay Area Air Quality Management District conducted a public hearing on June 21, 2023 in which they directed staff to submit the current versions of Rule 9-4 and Rule 9-6 to the United States Environmental Protection Agency and the California Air Resources Board for inclusion in the State Implementation Plan (SIP).
The Air District accepted written comments relating to the upcoming public hearing regarding whether to submit Rules 9-4 and 9-6 for inclusion in the SIP through May 12, 2023. A summary of the comments received and Air District responses are available below.
View other rule making activity |
|
|
|
Hearings, Workshops and Other Events
Documents
Comments
Updates Notification Subscription
Building Appliances Signup
Last Updated: 10/27/2025