Carbon Monoxide Safety for Houston Homes With Gas Furnaces
Carbon monoxide is colourless, odourless, and impossible to detect without equipment — which is why it is the most serious safety risk in a home with a gas furnace. Houston's pattern makes the risk worse: furnaces sit idle for eight months, then fire up on the first cold front, and a heat exchanger that cracked over the summer can leak exhaust into the home all winter. This guide covers where CO comes from, how to recognise the symptoms, and the testing and detectors that keep your family safe.
What Carbon Monoxide Is
Carbon monoxide (CO) is produced whenever fuel burns incompletely — in a gas furnace, a water heater, a stove, or a generator. It binds to haemoglobin far more readily than oxygen, so even low levels reduce the oxygen your body can carry. Because it has no smell and no colour, a home can have a dangerous CO problem with no warning at all, which is why detectors and annual testing matter more than vigilance alone.
Where CO Comes From in a Furnace
The most common furnace-related source is a cracked heat exchanger, which lets exhaust gases mix with the air blown through your ducts. A blocked or damaged flue can also trap exhaust inside the home, and dirty burners produce more CO than clean ones. Houston's long idle summers contribute: dust, rust, and corrosion build up while the furnace sits unused, and the first cold start of the season is when the damage shows up.
Symptoms You Should Never Ignore
Early CO exposure feels like the flu: headache, dizziness, nausea, and fatigue that improve when you leave the house and return when you come back. That pattern — feeling better away from home — is the classic warning sign. Higher exposure causes confusion, loss of coordination, and unconsciousness. If several people in the home feel ill at the same time, or symptoms clear when you step outside, leave the home and call 911 from outside.
Detectors: Placement and Maintenance
Every home with a gas furnace needs a carbon monoxide detector on every level, especially near bedrooms. Place them outside sleeping areas and near the furnace room, but not directly above the furnace or stove, where normal brief puffs can cause nuisance alarms. Test the alarm monthly, replace batteries yearly, and replace the whole detector every seven years — the sensor degrades even if the alarm still beeps on test.
What Professional CO Testing Involves
We test with a calibrated combustion analyser that measures CO in the flue gas and in the air around the furnace, at the supply registers, and near bedrooms. The readings are written on your report, so you have a baseline to compare against next year. If we find elevated CO, the furnace is shut down until the cause is fixed — a cracked exchanger or blocked flue has no safe workaround, and we will not run a furnace we know is leaking.
Prevention Before Winter
The cheapest CO protection is a pre-winter furnace inspection: heat exchanger checked, burners cleaned, flue verified clear, and CO readings recorded. It takes about an hour and it catches the problems that become emergencies in January. Book it in October, when there is still time to fix what we find, and make sure your detectors are current before the first cold front arrives.
The Bottom Line
Carbon monoxide gives no warning you can smell or see, which is why the protection has to be systematic: a working detector on every level, replaced every seven years, and a professional combustion test once a year before winter. Houston's long idle summers make the pre-winter inspection especially important — it is when a cracked heat exchanger or blocked flue is found, not in January when the furnace is running every night. If your CO alarm ever sounds, leave the home and call 911 from outside. To book a CO test or a pre-winter furnace inspection, call (281) 549-0799 — the diagnostic is free with any repair.
Carbon Monoxide Safety Beyond the Furnace
The furnace is the most common source of carbon monoxide in a Houston home, but it is not the only one. Gas water heaters share the same flue system in many homes, and a blocked flue affects both appliances at once. Gas stoves and ovens produce small amounts of CO during normal use, which is why they should never be used to heat a home — an oven left open for heat can raise indoor CO to dangerous levels within an hour. Portable generators are the most dangerous of all: never run one inside a garage, even with the door open, and keep it at least twenty feet from the house with the exhaust pointing away. After a winter storm, check that the furnace and water heater vents on the roof are clear of debris before restarting the system. And remember that a carbon monoxide detector only protects you if it is working — test it monthly, replace the batteries yearly, and replace the whole unit every seven years.
Finally, make sure everyone in the household knows what to do if the alarm sounds, especially at night. The plan is simple and worth rehearsing once: leave the home immediately, do not stop to open windows or search for the source, and call 911 from outside. Children and older adults are affected by carbon monoxide sooner than healthy adults, so a detector near the bedrooms matters more than one in the furnace room alone. If anyone feels ill — headache, dizziness, nausea — and the symptoms improve outside the home, treat it as an emergency even if the alarm has not sounded, because a detector can only warn about the levels it is designed to detect. When in doubt, get out and call for help.
At a Glance
| CO Source | Warning Sign | Action |
|---|---|---|
| Cracked heat exchanger | CO alarm, flu-like symptoms at home | Shut the furnace off; call immediately |
| Blocked flue | Soot around the furnace, poor draft | Do not run the furnace; book an inspection |
| Dirty burners | Yellow lazy flames, soot buildup | Schedule a cleaning and combustion test |
| No detector in the home | No warning at all | Install detectors on every level now |
| Detector over 7 years old | Sensor no longer reliable | Replace the detector |
Frequently Asked Questions
You cannot tell by smell — CO is odourless. A detector alarm, flu-like symptoms that clear outside the home, or soot around the furnace are the warning signs. A combustion analyser test gives a definitive answer.
On every level of the home, outside sleeping areas, and near the furnace room — but not directly above the furnace or stove.
Once a year, ideally as part of a pre-winter tune-up, so readings are checked before the heating season starts.
Leave the home immediately, call 911 from outside, and do not re-enter until emergency responders say it is safe. Do not open windows first or try to find the source yourself.
No — a heat pump moves heat electrically and burns no fuel, so it produces no CO. The risk comes from gas furnaces, water heaters, stoves, and generators.
Service Area
Same-day heating and AC service across the Houston metro, 24/7. If you need help with your furnace or heat pump, a stocked truck is already nearby.
We dispatch across Houston, TX, including ZIP codes 77002, 77003, 77004, 77005, 77006, 77007, 77008, 77009, 77019, 77027, 77056, 77057, 77063, 77077, 77079, 77080, 77081, 77082, 77084, 77090, 77095, 77098, 77099. Call (281) 549-0799 and we will route the nearest available technician to your door.
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