You cannot see or smell carbon monoxide, so a listed CO alarm on every level of the house is the only dependable way to know. The things you can watch for at a gas furnace are a yellow or fluttering burner flame, soot or heavy rust at the burner compartment or flue, and flu-like symptoms that ease when you leave the house. If a CO alarm sounds, get everyone outside and call 911 from outside. For a non-emergency inspection in Lubbock, call (414) 429-5333 and Hub City will connect you with an independent local HVAC pro.
Every fall in Lubbock, furnaces that sat untouched since March get asked to run all night. That is when combustion problems surface — and carbon monoxide is the one that gives no warning on its own.
What actually produces carbon monoxide in a house?
Carbon monoxide is a byproduct of burning fuel. Anything that burns natural gas, propane, wood, kerosene or charcoal makes some of it — in a typical Lubbock home that means the furnace, the water heater, a gas range, a fireplace, and a vehicle idling in an attached garage. Working normally, a furnace sends its combustion gases up the flue and out of the house.
Trouble starts when that path breaks down: a cracked or corroded heat exchanger, a flue pipe that is blocked, disconnected or rusted through, a vent that backdrafts instead of drawing, or an appliance starved of the air it needs to burn cleanly. A furnace running behind a filter choked with West Texas dust also runs hotter than it should, and years of that heat stress is one of the things that opens cracks in a heat exchanger.
What are the warning signs I can actually see?
None of these prove there is carbon monoxide in the house. They are the reasons to stop and get the system looked at:
- Flame color and behavior. On an older atmospheric furnace the burner flame should be crisp and blue. Yellow, lazy or flickering flames, or flames that roll or blow sideways when the blower kicks on, point to a combustion or airflow problem.
- Soot and rust. Black soot streaks, flaking rust or scorch marks around the burner compartment, the furnace cabinet or the flue connection are all signs that exhaust is not going where it should.
- The flue itself. A vent pipe that is loose at a joint, separated, crushed or visibly corroded needs attention before the season starts — and so does a bird or rodent nest at the termination, which is common after a long idle summer.
- Unexplained moisture. Heavy condensation on windows near the furnace or water heater, in a house that never had it, can mean combustion gases are staying inside.
- A pilot light that will not stay lit, or an older unit that keeps shutting itself down on a safety switch.
What do carbon monoxide symptoms feel like?
Low-level exposure feels like the flu without the fever: headache, dizziness, nausea, weakness, shortness of breath, and a heavy, foggy tiredness. Two patterns are the tell. More than one person in the house feels it at once, and pets seem off too. And the symptoms fade once you have been away for a while, then return when you are home again. Higher concentrations cause confusion, vomiting and loss of consciousness.
If you suspect exposure, get out into fresh air first and call for help from outside. Do not spend time hunting for the source.
Furnace acting up before the first cold snap?One call and we'll connect you with a local Lubbock HVAC pro.
📞 (414) 429-5333What should I do if the CO alarm goes off?
Treat it as real every time. Get everyone out of the house, pets included, then call 911 from outside. Do not open the windows first — airing the house out destroys the reading the fire department needs to find the source — and do not go back in for a phone or the dog's leash. Stay out until the fire department or the gas utility says the house is clear, and have the appliance inspected before it runs again. For sorting urgent from non-urgent problems generally, see our guide to what counts as an HVAC emergency in Lubbock.
How do I keep it from happening?
Three habits cover most of it.
- Working alarms, correctly placed. One on every level of the home and one outside each sleeping area, installed to the distances in the manufacturer's instructions. Test monthly, replace batteries on schedule, and check the date on the back — CO sensors expire, and an alarm past its service life should be replaced outright rather than re-batteried.
- An annual inspection before heating season. A pro checks the heat exchanger, the burners and the flue, and uses a combustion analyzer to measure what the furnace is actually producing — which is why heat-exchanger diagnosis is not a DIY job. Our fall furnace prep checklist covers what you can safely do yourself first.
- Keep airflow clean. Change the filter on schedule, especially during harvest season when South Plains air is loaded with field dust, and keep boxes and storage away from the furnace so it can draw combustion air.
Two things never to do: never use a gas range, oven or outdoor grill to heat the house, and never run a generator in a garage, shed or anywhere near an open window.
When is this a call-a-pro job?
Anything past looking and listening. Gas piping, burners, heat exchangers and venting are licensed-pro work, and a cracked heat exchanger can only be confirmed by inspection and combustion testing. If you have seen any of the signs above, shut the system down and have it checked before running it again. Hub City is a referral service, not a contractor: call and we will connect you with an independent local pro for furnace and heating service, or use the callback request form. If you smell gas or an alarm is sounding, call 911 or your gas utility first — that call comes before ours.
Frequently asked questions
What should I do if my carbon monoxide alarm goes off?
Get everyone, pets included, outside into fresh air, then call 911 from outside. Do not open windows and wait to see whether the alarm resets, and do not go back inside for anything until the fire department or the gas utility says the house is clear. If anyone is dizzy, confused, nauseated or unusually sleepy, tell the dispatcher that too.
Can I smell carbon monoxide from my furnace?
No. Carbon monoxide is colorless, odorless and tasteless, which is exactly why a working alarm is the only reliable way to detect it. The rotten-egg or sulfur smell people associate with gas is an odorant added to natural gas itself, so it warns you about a gas leak, not about carbon monoxide.
What are the warning signs of a cracked heat exchanger?
Common clues are a burner flame that flutters or rolls when the blower starts, soot or heavy rust around the burner compartment, a flame that burns yellow rather than crisp blue on an older atmospheric furnace, and a carbon monoxide alarm that sounds only while the furnace is running. None of these confirms a crack on their own. A pro has to inspect the exchanger and test combustion.
Where should carbon monoxide alarms go in my house?
Put one on every level of the home and one outside each sleeping area, and follow the placement distances in your alarm's instructions. Test them monthly, change the batteries on schedule, and check the manufacture date stamped on the back, because the sensor inside has a limited service life and the whole unit has to be replaced once it expires.
Is my furnace more likely to have a problem after sitting all summer in Lubbock?
A Lubbock furnace typically sits unused for months while West Texas dust settles through it, and dust on the burners, the flame sensor and the heat exchanger affects how cleanly it burns. Rodents and birds can also block a flue over the summer. That is why a fall inspection before the first cold night is worth scheduling.