Regional air district adopts rule phasing out gas-fired heating appliances

Description: In March of 2023 the Bay Area Air Quality Management District (BAAQMD) adopted first-in-nation rules to phase out and eventually prohibit the sale of new natural gas-fired water heaters and furnaces. Beginning in 2027 only zero-emission, electric water heaters can be sold or installed in Bay Area homes or businesses. Similarly, the effective date for allowing only zero-emission furnaces to be sold or installed is 2029, and 2031 for sale or installation of zero-emission large commercial water heaters. The rules apply to only new equipment installations and do not mandate retrofitting existing equipment.

The rules will reduce the emission of climate and air pollutants created by the combustion of natural gas, improving air quality and the health and safety for residents in the nine-county San Francisco Bay region. BAAQMD’s rule 9-4 regulates nitrogen oxide emissions from natural gas-fired furnaces and rule 9-6 regulates nitrogen oxide emissions from natural gas-fired boilers and water heaters. These sources generate more nitrogen oxides, collectively termed NOx, than passenger vehicles in the San Francisco Bay Area.

The adopted rules were the result of efforts outlined in BAAQMD’s 2017 Clean Air Plan, which addressed the Bay Area’s non-attainment status relative to state and national air quality standards for ozone and particulate matter. Nitrogen dioxide (NO2) along with NOx react with other chemicals in the air to form both fine particulate matter (PM2.5) and ozone, which are associated with respiratory problems and asthma, and harmful when inhaled. Longer and more severe heat waves associated with climate change are expected to cause more ozone formation, resulting in more frequent exceedances of ozone standards.

Nitrogen oxide molecules are formed in essentially all combustion processes. NOx molecules include:

  • nitric oxide (NO), which is subsequently oxidized to nitrogen dioxide (NO2) in the atmosphere,
  • nitrogen dioxide (NO2), and
  • nitrous oxide (N2O).

Nitric oxide and nitrogen dioxide are acid rain precursors and participate in the formation of ozone and the generation of photochemical smog, while nitrous oxide is a greenhouse gas with a 20-year global warming potential nearly 300 times greater than carbon dioxide. In California nearly 90 percent of building NOx emissions are due to space and water heating and the remaining 10 percent are due to natural gas combustion for cooking, clothes drying, and other miscellaneous end uses.

Adoption of the rules followed a two-year period of stakeholder working group meetings, drafting and review of amendments to existing rules 9-4 and 9-6, public workshops to review draft amendments, and public review and comment on a draft environmental impact report. Implementation of the revised rules will include formation of an Implementation Working Group that will periodically report back to the BAAQMD Board on technical readiness and equitable transition. The working group will include the following stakeholder groups:

  • environmental justice groups
  • community-based organizations
  • tenant and landlord groups
  • affordable housing developers
  • building management firms
  • labor and trade organizations
  • technology manufacturers
  • subject matter experts/building energy advocates
  • technology entrepreneurs focused on home electrification at scale
  • local governments
  • state agencies
  • utility and energy service providers

Goal: Improve ambient air quality by:

  • reducing NOx emissions from buildings
  • reducing ozone concentrations
  • reducing concentrations of airborne fine particulate matter (PM2.5)


  • net reduction in ambient air concentrations of NOx, ozone, and fine particulate matter (PM2.5)
  • net reduction in natural gas use in buildings

Time to Implement: 2 years to draft and adopt rule amendments


2023 March Final Staff Report – Proposed Amendments to Building Appliance Rules 9-4 and 9-6

Text of proposed amendment: Rule 9-4

Text of proposed amendment: Rule 9-6

2022 Sept. State Strategy for the State Implementation Plan

Furnace and Water Heater Fact Sheet

2021 Sept. Workshop Report Rule 9-4 and 9-6

Final 2017 Clean Air Plan Volume 1

Additional Information:

Bay Area Regulators Approve Rules to Phase Out Gas Furnaces and Water Heaters

Bay Area officials vote to ditch new gas furnaces and water heaters

Bay Area to phase out sale of gas heating appliances, in first-in-nation step to clean up smog

Health Effects of Ozone in Patients with Asthma and Other Chronic Respiratory Disease

Basic Information about NO2

History of California’s Ambient Air Quality Standards

Regional air districts adopt Climate Action Plans

Contact Info:
Jennifer Elwell
Bay Area Air Quality Management District
Senior Air Quality Engineer Rules & Strategic Policy Division
(415) 749-8732

Sectors(s) Air Pollution Agencies, Buildings
Location(s) , , , , , , , ,
Date First Adopted March 15, 2023
Last Updated March 23, 2023
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