Building Appliances Rule Implementation

Learn about the Air District’s zero-NOx space and water heating rules.

Rule Background

Air District staff developed amendments to Rule 9-4: Nitrogen Oxides from Fan Type Residential Central Furnaces and Rule 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 these rules were adopted by the Air District Board of Directors in March 2023 introducing a zero-NOx requirement for newly installed furnaces and water heaters in the Bay Area with compliance dates beginning with small water heaters manufactured after January 1, 2027. Additional information on the rule amendments can be found on the Building Appliance Rules web page as well as in the following documents:

As part of the rule implementation, the Air District has convened an Implementation Working Group, or IWG, made up of external stakeholders. More information on the IWG, including meetings and materials can be found on the Building Appliance Implementation Working Group web page.

These rule amendments apply to residential and commercial furnaces and water heaters, and no other natural gas appliances. Under these rules, water heaters and gas furnaces would have to meet zero-emission standards for oxides of nitrogen, or NOx. The only commercially available appliances that currently meet those standards are electric, but if a natural gas appliance demonstrates that it meets the standards, it would be allowed under the proposed amendments.

Compliance Dates

Ultra-low NOx standard implementation date (applies to appliances manufactured after the noted date):

  • Jan. 1, 2024 – For residential fan-type central furnaces. This standard matches existing standards in other large California air districts, and natural gas appliances are currently available to meet this standard.

Zero NOx standard implementation dates (applies to appliances manufactured after the noted date):

  • Jan. 1, 2027 – Water heaters less than 75,000 BTU/hr (typically residential tank water heaters)
  • Jan. 1, 2029 – Residential and commercial furnaces
  • Jan. 1, 2031 – Water heaters between 75,000 and 2 million BTU/hr (commercial and multifamily). This standard includes instantaneous or tankless water heaters.

Locations Required to Comply

These rules apply within the Bay Area Air Quality Management District’s jurisdiction which includes Alameda, Contra Costa, Marin, San Francisco, San Mateo, Santa Clara, southwestern Solano and southern Sonoma counties.

View maps showing the area of the Air District on the Interactive Maps web page.

The California Air Resources Board is currently working on draft regulations that would also impact building appliances. This process is ongoing and information can be found on this web page.

Resources and Incentives

The following resources provide guidance on electric appliance purchase and installation, supporting compliance with the rules.

Residents: Learn about transitioning to electric appliances, including incentives and financing and qualified contractors through The Switch is On.  

Contractors and Building Professionals: Learn about on-demand and in-person training, becoming a qualified contractor, and understanding incentive programs

Spare the Air Status

Last Updated: 5/8/2024