The Air District's zero-NOx rule
Your gas furnace can stay. Its replacement might not be gas.
The Bay Area Air District has set a zero-NOx standard for natural gas furnaces. It doesn't force a working furnace out; it changes what can be sold and installed once yours wears out. Here's what it says, and what is still being reviewed.
At a glance
Gas furnaces under Rule 9-4
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2029
the furnace date
A natural gas furnace manufactured after January 1, 2029, must emit no nitrogen oxides.
Source: Bay Area Air District, Regulation 9 Rule 4 (adopted March 15, 2023), last checked 2026-10-22.
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Burnout
not removal
The requirements apply only when your current furnace burns out and is replaced.
Source: Bay Area Air Quality Management District, Rules 9-4 and 9-6 Building Appliances, last checked 2026-10-22.
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Installers
are bound too
It applies to anyone who sells, installs or offers a natural gas furnace for use in the Bay Area.
Source: Bay Area Air District, Regulation 9 Rule 4 (adopted March 15, 2023), last checked 2026-10-22.
What the rule actually does
Once each compliance date arrives, gas appliances the rules cover can't be sold or installed anywhere in the Bay Area if they emit NOx. For furnaces the date follows manufacture, so a furnace made before January 1, 2029, isn't held to the standard.
The rule is written for the people who sell and install furnaces, not only the people who make them.
Source: Bay Area Air District, Frequently Asked Questions on the Appliance Rules (July 2026). Rules and programs change: last checked 2026-10-22.
Source: Bay Area Air District, Regulation 9 Rule 4 (adopted March 15, 2023). Rules and programs change: last checked 2026-10-22.
What it leaves alone
From the Air District's own answers:
- A furnace that still works: the requirements apply only upon burnout.
- Propane furnaces and water heaters: only natural gas equipment is covered.
- Mobile homes: their furnaces and water heaters are exempt from the zero-NOx requirements.
Source: Bay Area Air Quality Management District, Rules 9-4 and 9-6 Building Appliances. Rules and programs change: last checked 2026-10-22.
Source: Bay Area Air District, Frequently Asked Questions on the Appliance Rules (July 2026). Rules and programs change: last checked 2026-10-22.
Source: Bay Area Air District, Appliance Rules Myths vs. Facts (September 2026). Rules and programs change: last checked 2026-10-22.
What could still change
The furnace date isn't settled in every detail. A cost and technology assessment for furnaces will be completed before the 2029 compliance date, and the furnace rule is the focus of the working group's second phase.
Water heaters are on their own track: on November 4th, 2026 the Air District's board considers changes to that rule, including some exemptions and a later compliance date.
Source: Bay Area Air District, Appliance Rules Myths vs. Facts (September 2026). Rules and programs change: last checked 2026-10-22.
Source: Bay Area Air Quality Management District, Rules 9-4 and 9-6 Building Appliances. Rules and programs change: last checked 2026-10-22.
What most homes will put in instead
Until gas furnaces that meet the standard exist, the Air District expects most people to comply with an electric heat pump.
Source: Bay Area Air District, Frequently Asked Questions on the Appliance Rules (July 2026). Rules and programs change: last checked 2026-10-22.
Your furnace
What the rule means for you this winter
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Is your gas furnace still working?
If yes
Nothing has to change
The rule doesn't make anyone pull out working equipment. Keep it maintained and plan the next system on your own schedule.
Furnace repairIf no
Then the replacement is the decision
A gas furnace is still allowed today. It's also the moment to price a heat pump beside it.
Furnace replacement -
Does the house use both heating and cooling?
If yes
A heat pump may cost less to run
The Air District says heat pump space conditioning is generally cheaper for larger homes that use both.
Heat pump installationIf no
Compare both on your numbers
If you only heat, price the furnace and the heat pump side by side.
Heat pump or gas furnace
Tell us what it's doing. We'll take it from there.
Call and describe the problem: the noise, the smell, the room that never warms up. Or book a visit online.
