Rules 9-4 and 9-6 Building Appliances

Background and Resources: Existing Supporting Documents

• Water Heater Rule Draft Amendments Overview (337 Kb PDF, 2 pgs, posted 10/26/2026)(Updated October 2026) 
• New Myths vs Facts Sheet (329 Kb PDF, 2 pgs, posted 10/26/2026)(Updated October 2026)
• Frequently Asked Questions – Adopted Amendments to Rules 9-4 and 9-6 (607 Kb PDF, 5 pgs, revised 7/14/2026)(Updated July 2026)
• Fact Sheet – Proposed Amendments to Rules 9-4 and 9-6(177 Kb PDF, 1 pg, revised 7/14/2026) (Updated July 2026)
• Know the Facts Webpage (Posted May 2026)
• Overview of Rule 9-6 Concepts Paper (185 Kb PDF, 1 pg, revised 12/4/2025)(Posted December 2025)

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)

Rule Implementation Webpages and Resources 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.  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.

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:

• Building Appliances Implementation Working Group webpage

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:

• Building Appliances Rule Implementation webpage

Regulatory Language and Staff Report for Rule 9-6 Amendments (November 2026)

Staff have released Regulatory Language, a Staff Report, an Updated Socioeconomic Impact Analysis, and an Addendum to the Environmental Impact Report for the flexibility amendments to Rule 9-6 addressing small water heaters (< 75,000 BTU/hour). The documents can be found below:

• Notice of Public Hearing(114 Kb PDF, 2 pgs, revised 10/2/2026)
• Regulatory Language(234 Kb PDF, 11 pgs, posted 10/30/2026)
• Staff Report(1 Mb PDF, 56 pgs, posted 10/30/2026)
• Socioeconomic Impact Analysis(611 Kb PDF, 33 pgs, posted 10/30/2026)
• Appendix A: Analysis of Proposed Amendments to Rule 9-6 by Race, Ethnicity, and County(195 Kb PDF, 4 pgs, posted 10/30/2026)
• Addendum to the Environmental Impact Report(230 Kb PDF, 25 pgs, posted 10/30/2026)
• Memorandum: Small Water Heater Incremental and Total Upfront Costs(371 Kb PDF, 8 pgs, posted 10/30/2026)

Proposed Regulatory Language and Preliminary Staff Report for Rule 9-6 Amendments (October 2026)

Staff have released Proposed Regulatory Language, a Preliminary Staff Report, an Updated Socioeconomic Impact Analysis, and an Addendum to the Environmental Impact Report for flexibility amendments to Rule 9-6 addressing small water heaters (<75,000 BTU/hour). The documents can be found below:

• Notice of Public Hearing(114 Kb PDF, 2 pgs, revised 10/2/2026)
• Proposed Regulatory Language(235 Kb PDF, 11 pgs, revised 10/2/2026) 
• Preliminary Staff Report(1 Mb PDF, 54 pgs, posted 10/2/2026)
• Updated Socioeconomic Impact Analysis(601 Kb PDF, 32 pgs, revised 10/2/2026)
• Addendum to the Environmental Impact Report(265 Kb PDF, 24 pgs, revised 10/2/2026) 

Draft Regulatory Language and Updated Regulatory Overview for Rule 9-6 Amendments (July 2026)

Staff have released Draft Regulatory Language and an Updated Regulatory Overview for flexibility amendments to Rule 9-6 addressing small water heaters (<75,000 BTU/hour). The documents can be found below:

• Draft Regulatory Language(232 Kb PDF, 11 pgs, revised 7/14/2026)
• Updated Regulatory Overview(1 Mb PDF, 39 pgs, revised 7/14/2026) 

A one-page overview of this rule amendment effort, including background information, key proposed changes, and the anticipated timeline is available below:

• Water Heater Rule Draft Amendments Overview - July 2026 (338 Kb PDF, 2 pgs, posted 7/17/2026)( English | tiếng Việt | Español | 中文 )

Regulatory Overview: Rule 9-6 Flexibility Amendments Report (May 2026)

Staff presented updated flexibility and affordability concepts to Rule 9-6 at the May 6th and May 13th Board of Directors meetings. In advance of the presentation staff released an informational document titled Regulatory Overview: Rule 9-6 Flexibility Amendments ("Regulatory Overview")  which is intended to give the public and Board members additional context on staff's process-to-date and current recommendations. 

The Regulatory Overview provides background on potential amendments to Rule 9-6, including key considerations related to exemptions, potential implementation challenges, and key factors such as income-based eligibility and building or project constraints.

The May presentations included discussions of draft concepts related to the potential amendments to the zero NOx requirements in Rule 9-6 for small water heaters and staff’s recommendations. The concepts were last discussed at the February 2026 Stationary Source Committee meeting. The May 6th meeting included a dedicated time for public comment, the May 13th meeting was a continuation of the previous one due to loss of quorum.

• A copy of the Regulatory Overview Report can be found here.(1 Mb PDF, 36 pgs, revised 4/13/2026)

Rule 9-6 Concepts Paper (2025)

In October 2025, the Air District released a Concepts Paper for potential amendments to Rule 9-6 (Nitrogen Oxides from Natural Gas-Fired Water Heaters). These potential amendments 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 upon burn out. The 30-day public comment period is now closed. Comments received were discussed at the December 10, 2025 Stationary Source Meeting.

• Concepts Paper(6 Mb PDF, 29 pgs, posted 10/24/2025)

Rule 9-6 Implementation Report (2024)

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:

• Staff Report - Informational Update Regarding Regulation 9, Rule 6(1 Mb PDF, 58 pgs, posted 11/27/2024)

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 (2023)

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(614 Kb PDF, 5 pgs, posted 7/29/2026)
• Fact Sheet – Proposed Amendments to Rules 9-4 and 9-6(182 Kb PDF, 1 pg, posted 7/29/2026)
• Infographics – Proposed Amendments to Rules 9-4 and 9-6(115 Kb PDF, 1 pg, posted 3/16/2023)
• Notice of Public Hearing and Notice of Availability of DEIR(268 Kb PDF, 2 pgs, posted 12/19/2022)
• Final Environmental Impact Report for Proposed Amendments to Rule 9-4 and Rule 9-6(9 Mb PDF, 184 pgs, posted 3/7/2023)
• Staff Report – Proposed Amendments to Building Appliance Rules – Regulation 9, Rule 4 and Rule 6(878 Kb PDF, 54 pgs, posted 3/7/2023)
  • Appendix A: Proposed Amendments to Rule 9-4(581 Kb PDF, 7 pgs, revised 12/20/2022)
  • Appendix B: Proposed Amendments to Rule 9-6(437 Kb PDF, 6 pgs, revised 12/20/2022)
  • Appendix C: Socioeconomic Impacts Analysis(1004 Kb PDF, 37 pgs, revised 12/20/2022)
  • Appendix D: Electric Infrastructure Impacts from Proposed Zero NOx Standards(1 Mb PDF, 38 pgs, revised 12/20/2022)
  • Appendix E: Assessing Ambient Air Quality and Health Impacts from Natural Gas Building Appliances in the Bay Area(5 Mb PDF, 40 pgs, posted 12/19/2022)
  • Appendix F: Exposure and Equity Assessment of Natural Gas Appliances in the San Francisco Bay Area(17 Mb PDF, 17 pgs, revised 12/20/2022)
  • Appendix G: Draft Environmental Impact Report(10 Mb PDF, 295 pgs, posted 12/19/2022)
  • Appendix H: Response to Comments(1 Mb PDF, 932 pgs, posted 3/7/2023)

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). 

• Notice of a Public Hearing – Submission of Rule 9-4 and Rule 9-6 to the SIP (98 Kb PDF, 1 pg, posted 4/5/2023)

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.

• Response to Comments: Submittal of Rules 9-4 and 9-6 to SIP(216 Kb PDF, 5 pgs, posted 6/23/2023)

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.