Home Safety · Winter
Furnace & Carbon Monoxide Safety for Missouri Homes
Carbon monoxide is colorless and odorless, and in a Missouri winter the usual sources are the fuel-burning equipment working hardest: the furnace, a gas water heater, a fireplace, or a car idling in an attached garage. Working CO alarms plus a furnace that's inspected before heating season are the two defenses that actually matter.
The short version
- CO alarms belong outside every sleeping area and on every level of the home, and they expire; check the manufacture date on the back.
- The alarm's test button tests the horn and battery, not the sensor. An expired unit can still chirp on test and fail to detect CO.
- A cracked heat exchanger or blocked flue is the classic furnace-side CO source, neither is visible from outside the unit.
- If the alarm sounds: everyone out to fresh air, then 911 from outside. Treat it like a gas leak, not a nuisance.
- Never run generators, grills, or patio heaters indoors or in the garage, including during ice-storm power outages.
Where CO comes from in a typical O'Fallon home
Any appliance that burns fuel produces carbon monoxide; the danger starts when it stops venting outdoors the way it should. The furnace is the biggest fuel burner in the house and runs the longest hours in January, which is why heating equipment tops the list, a heat exchanger that has cracked with age, a flue blocked by debris or a nest, or venting knocked loose can spill combustion gases into the air your blower then circulates through every room.
Alarm placement and upkeep that actually protects
Placement and age matter more than brand:
- Outside every sleeping area, CO poisoning at night is the scenario alarms exist for.
- On every level, including the basement where the furnace and water heater usually live.
- Near, but not directly beside, fuel-burning appliances and the door to an attached garage.
- Test monthly with the button; replace batteries on a schedule (clock-change weekends are an easy habit).
- Replace the whole unit at the age printed on its back, the sensor degrades even if the test button still beeps.
The furnace side: what an inspection catches
You can't see a heat exchanger crack from outside the furnace, and CO problems rarely announce themselves before the alarm does. During a heating tune-up, Swiss Air technicians inspect the heat exchanger, check burner flame quality, verify the flue is drafting correctly, and test combustion, exactly the failure points that turn a furnace into a CO source. Soot streaks, repeated pilot outages, excess moisture on windows, and a yellow, lazy burner flame instead of a crisp blue one are all reasons to have it looked at before winter.
When the alarm sounds
Get everyone, and pets, out to fresh air and call 911 from outside. Don't pause to open windows or hunt for a source, and say so on the call if anyone feels headachy, dizzy, nauseated, or unusually sleepy; responders treat that differently. Don't run the furnace or any fuel-burning appliance again until it has been professionally inspected. An intermittent chirp (rather than a full alarm) usually means battery or end-of-life, still a today problem, just not an evacuation.
Quick answers
Frequently asked
- How many CO alarms does my house actually need?
- At minimum: one outside each sleeping area and one on every level, including the basement. Homes with an attached garage or multiple fuel-burning appliances benefit from coverage near those, too. Interconnected alarms, when one sounds, all sound, give the earliest warning in multi-level homes.
- Can my furnace produce CO even if it seems to run fine?
- Yes, that's what makes CO dangerous. A heat-exchanger crack or a partially blocked flue doesn't necessarily change how the furnace feels from the vents. The failure points are internal, which is why combustion testing and heat-exchanger inspection are part of a proper fall tune-up rather than something you can eyeball.
- My CO alarm went off once and stopped. Do I still need to do anything?
- Yes. Treat any full alarm as real: ventilate only after everyone is out, and have the fuel-burning equipment inspected before trusting the house again. Alarms respond to accumulating concentration, so a brief alarm can mean a source that hasn't peaked yet, a car warming in the garage, a backdrafting water heater, a furnace starting to fail.
Have the furnace inspected before it matters
A heating tune-up includes the heat-exchanger inspection, combustion check, and flue verification this guide describes, and USA Savings Club members get it on a schedule, automatically.