Carbon Monoxide Safety With Gas Furnaces in Older San Gabriel Valley Homes
The alarm, the annual inspection and the three warning signs that mean leave the house now.
By Piggies Air Conditioning HVAC Team · Updated · 5 min read · Safety & Ownership
The short answer
Carbon monoxide is a colorless, odorless gas produced when fuel burns incompletely or exhaust cannot leave the house. California requires CO alarms in homes with gas appliances or an attached garage. If an alarm sounds, get everyone outside, call 911 from outside, and stay out until the source is found. A yearly furnace inspection is the best prevention.
How CO gets into living space
- A cracked or corroded heat exchanger lets combustion gases mix with the air the blower sends to the rooms.
- A blocked, disconnected or corroded flue cannot carry exhaust outside. Birds' nests, collapsed vent pipe in the attic and rusted draft hoods are common in homes built before the 1980s.
- Backdrafting: a powerful range hood, dryer or bathroom fan can pull exhaust back down the flue of a natural-draft furnace or water heater, especially in a tight house with the windows closed.
- A furnace closet or garage that is sealed off from the air the burner needs starves the flame and produces more CO.
Alarms: what the law asks and what works
California's Carbon Monoxide Poisoning Prevention Act requires CO alarms in dwellings that have a fossil-fuel appliance, a fireplace or an attached garage. Place one outside each sleeping area and on every level, including the basement if you have one. Alarms have a printed end-of-life date and stop working after it; replace them on schedule, and test monthly.
Plug-in and battery alarms count. If you add a combination smoke and CO alarm, mount it where the manufacturer specifies; CO mixes evenly with air, so height is less critical than for smoke.
Symptoms that are easy to mistake for the flu
Headache, dizziness, nausea, weakness and confusion are the early signs. The tell is the pattern: everyone in the house feels off at the same time, symptoms ease when you leave, and there is no fever. Pets often show it first. Treat that pattern as a CO event even if the alarm has not sounded.
What a furnace safety inspection covers
If an inspection finds a cracked heat exchanger, the furnace should be shut down until it is repaired or replaced. That is not an upsell; it is the one finding that justifies the word "unsafe".
- Heat exchanger inspection, including a camera or combustion analysis when the design hides the exchanger.
- Flue and vent connector condition, slope and termination.
- Combustion air openings and clearances in the furnace closet.
- Burner flame quality, gas pressure and the limit and rollout switches.
- A CO reading in the supply air and in the room while the furnace runs.
What to remember
- 1 Alarms outside each sleeping area, replaced by their printed date.
- 2 Same-time symptoms that fade outdoors are a CO pattern.
- 3 An annual inspection with a combustion check is the prevention.
This guide is general information for homeowners in Baldwin Park and surrounding communities. Codes, rates and incentive programs change; confirm current terms with the agency or program before relying on a date or amount. For your specific system, book a visit or call us.
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