Rules 9-4 and 9-6 Building Appliances
Learn about Regulation 9, Rules 4 and 6 to reduce emissions of nitrogen oxides from residential and commercial furnaces and water heaters in buildings in the Bay Area.
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 from the implementation working group.
Update: Staff is currently planning to present to the Stationary Source Committee in December 2025 to share updated concepts on further amendments to Rule 9-6. Staff is planning to release a Draft Concepts Paper prior to the meeting, followed by a public comment period.
The Air District is preparing a Draft Concepts Paper for potential amendments to Rule 9-6 (Nitrogen Oxides from Natural Gas-Fired Water Heaters). These changes are intended to provide additional flexibility and ensure a smooth transition as older appliances are replaced with cleaner options.
A public workshop will be held in Early 2026 to discuss concepts, hear feedback, and answer questions from the community and stakeholders.
- See our newly developed Myths vs. Facts Sheet for a quick summary of current rule requirements.
- For details on past meetings and workshops visit the Implementation Working Group webpage and Hearings, Workshops, and 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:
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Background and Resources: New Supporting Documents
Existing Supporting Documents
- Frequently Asked Questions – Adopted Amendments to Rules 9-4 and 9-6
- Fact Sheet – Proposed Amendments to Rules 9-4 and 9-6
Rule Development History
Rule 9-6: Nitrogen Oxides Emissions from Natural Gas-Fired Boilers and Water Heaters was first adopted over thirty years ago and later amended in 2007. Rule 9-6 was established to reduce nitrogen oxide (NOx) emissions from residential water heating. Rule 9-4: Nitrogen Oxides from Fan Type Residential Central Furnaces was also originally adopted over thirty years ago and applies to small residential and commercial furnaces. Together, these rules form a key part of the Air District’s strategy to reduce emissions from buildings. In recent years, staff have been evaluating updates to both rules to reflect new technologies and support the region’s clean air and climate goals.
- In March of 2023, Air District staff developed amendments to existing rules Rules 9-4 and 9-6. 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. These requirements include zero NOx emissions standards with a future implementation date beginning in 2027, 2029, and 2031, depending on size and equipment type. These new requirements apply only upon burn out of one’s current equipment. Additionally, any equipment manufactured after the new implementation date will be subject to the new standards.
- In December of 2024, Air District staff presented an informational update on the implementation readiness of the zero NOx requirements for residential water heaters (Rule 9-6) to the Air District Board of Directors.
- In April of 2025, Air District staff presented to the Stationary Source Committee to share proposed next steps and potential flexibilities and amendments to Rule 9-6 (2027 compliance date) based on the IWG’s findings. The second phase of the IWG 2.0 will commence in late-2025 and will focus on furnaces Rule 9-4 (2029 compliance date).
Implementation Working Group (IWG)
As part of the recent 2023 amendments, the Air District committed to convene the Implementation Working Group (IWG). The IWG is 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 will provide a forum for invited members to discuss technical and equity aspects of implementing the Building Appliances Rules.
Air District staff hosted over twenty IWG meetings from May 2023 to August 2024, including plenary, steering committee, and equity focused meetings. The first five public plenary IWG meetings focused on requirements for small water heaters (Rule 9-6) and took place virtually via Zoom in 2023 and 2024. The last IWG meeting took place virtually on August 20, 2024 from 1-4 PM. Utilizing the IWG feedback and professional research solicited over the course of this IWG process, staff published and released a board report in December 2024, linked in the section below.
Rule Implementation Webpages and Resources
Staff have recently established a suite of dedicated webpages to house all information from past internal working group meetings. Agendas, research performed by consultants, and a list of current IWG members can be found at the link below:
Additional general information regarding the Building Appliances Rule Implementation, including fact sheets, compliance dates, and supporting resources and incentives can be found at the link below:
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, and December 11, 2024. Air District staff summarized information gathered during the implementation working group process, along with all professional research solicited, and published a board report which can be found at the link below:
This report highlights the main findings across the following categories researched:
- Market Development
- Grid and Reliability Impacts
- Workforce
- Permitting
- Costs
- Challenging Installation Cases
- Potential Housing Impacts
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'.
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.
Hearings, Workshops and Other Events
Throughout the rule development process, we provide information on upcoming and past workshops, hearings, and other events.
Documents
Supporting materials, such as staff reports, regulatory language, and other technical documents related to rule development, are posted throughout the development process.
Comments
The Air District provides opportunities for the public to submit comments throughout the development process, and posts comments received during the open public comment periods.
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Last Updated: 2025/10/1