Carbon monoxide alarms and gas heat
A gas furnace means a CO alarm. The law says so.
California requires a carbon monoxide alarm in every home with a gas appliance, a fireplace or an attached garage. Here's what the law and the safety agencies say, and what a permit can bring with it.
The short version
What the rules say about CO alarms
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2011
for homes already standing
The law reached existing single-family homes by July 1, 2011.
Source: California Legislature, SB 183 (2010) chaptered text, last checked 2026-10-22.
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Every level
and outside sleeping areas
The safety commission's advice: alarms that run on batteries, or have a battery backup.
Source: U.S. Consumer Product Safety Commission, Carbon Monoxide Questions and Answers, last checked 2026-10-22.
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Not here
kitchens, or above a gas appliance
The same commission doesn't recommend mounting a CO alarm in either spot.
Source: U.S. Consumer Product Safety Commission, Carbon Monoxide Questions and Answers, last checked 2026-10-22.
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$1,000
permit value, San Mateo
Over that, a residential permit under San Mateo Consolidated Fire brings smoke and CO alarms with it.
Source: San Mateo Consolidated Fire, Smoke and CO Detector Handout (revised 7/26/19), last checked 2026-10-22.
The rules, in full
Where the CO alarm rules come from
Each is quoted from its source, with the date we last read it.
On file, last checked 2026-10-22
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California
Who has to have one
The owner of a home with a fossil fuel heater or appliance, a fireplace or an attached garage must install a carbon monoxide device approved and listed by the State Fire Marshal.
Source: California Health and Safety Code, section 17926. Rules and programs change: last checked 2026-10-22.
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San Mateo
A permit can bring it up
Since January 1st, 2011, San Mateo Consolidated Fire has required smoke and carbon monoxide alarms throughout the home on residential permits valued over $1000, so a furnace replacement permit above that brings the alarms with it.
Source: San Mateo Consolidated Fire, Smoke and CO Detector Handout (revised 7/26/19). Rules and programs change: last checked 2026-10-22.
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PG&E
A yearly look at the furnace
PG&E's advice is to have a qualified professional maintain and inspect heating systems and other fuel-burning appliances every year.
Source: PG&E, Carbon Monoxide Safety. Rules and programs change: last checked 2026-10-22.
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PG&E
If you suspect carbon monoxide
If it's safe to, turn off the gas appliance you suspect and open the windows.
The safety commission puts the alarm itself plainly: never ignore one that's going off.
Source: PG&E, Carbon Monoxide Safety. Rules and programs change: last checked 2026-10-22.
Source: U.S. Consumer Product Safety Commission, Carbon Monoxide Questions and Answers. Rules and programs change: last checked 2026-10-22.
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PG&E
If you smell gas instead
Leave the area now and call 9-1-1, then call PG&E.
Source: PG&E, Gas Safety. Rules and programs change: last checked 2026-10-22.
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.
