The story we tell new techs: a customer in Friendswood called us in January with "the heat does not feel right." Her 14-year-old furnace had a hairline crack in the heat exchanger. Carbon monoxide was leaking into the supply air at low levels. She had been getting headaches for weeks and assumed it was stress. We caught it on the combustion test before her detector ever sounded. That is why we test every furnace, every visit.
Where CO comes from in a Houston home
CO is a byproduct of incomplete combustion. Anything that burns natural gas, propane, oil, gasoline, charcoal, or wood can produce it:
- Gas furnace (especially with a cracked heat exchanger or blocked flue)
- Gas water heater (failing draft, blocked vent, back-drafting from a tightly sealed home)
- Gas range or oven (especially when used as a heat source, which is a real bad idea)
- Gas fireplace (blocked flue, damper closed)
- Attached garage with a vehicle running (CO seeps into the house through the wall)
- Portable generator placed indoors or near an open window during a power outage
- Charcoal grill or camp stove used inside (kills people every year)
Symptoms to recognize
Per the CDC, low-level CO exposure causes:
- Headache
- Dizziness
- Nausea
- Shortness of breath
- Confusion or trouble concentrating
Higher exposure causes vomiting, severe headache, loss of consciousness, and death. The symptoms feel like the flu, which is why mild CO often goes undetected. Tell: symptoms get better when you leave the house and worse when you return.
Detector placement and care
- One detector on every level of the home, including the basement (rare in Houston) and finished attic.
- One outside each sleeping area, where it can wake people up.
- Mount at eye level. CO mixes with air; it does not rise like smoke.
- Avoid placing within 15 feet of cooking or fuel-burning appliances (false alarms).
- Test monthly. Replace batteries with smoke alarms each spring and fall.
- Replace the entire detector every 5 to 7 years per most manufacturers. Sensors degrade.
What to do if your detector sounds
- Get everyone outside immediately, including pets. Do not stop to gather things.
- Call 911 from outside.
- Do not re-enter until the fire department clears the home.
- Once cleared, call your HVAC company. The detector found a source. The source needs to be identified and fixed before you turn fuel-burning equipment back on.
The annual checks that prevent the problem
Every fall, before the heat runs much, have a tech do a real combustion safety check on the furnace and water heater. What we check:
- Heat exchanger for cracks (visual + sometimes camera scope)
- Flue and venting for blockage, separation, or back-pitch
- Combustion air supply (a too-tight home can starve the appliance)
- Burner condition and flame characteristics
- Draft test under both furnace-only and worst-case scenarios (e.g., kitchen exhaust + dryer running)
- Ambient CO reading in the house and at each appliance
This is part of a real tune-up. If you have ever had a $59 "tune-up" that did not include combustion testing, you did not get a real tune-up.
One more thing on hurricane season
Most Houston-area CO fatalities cluster around hurricanes when people run portable generators. Generators must be outside, at least 20 feet from the house, with the exhaust pointed away from doors and windows. Never inside a garage, even with the door open. Never on a porch or in a breezeway. The CO concentration around a running generator is genuinely lethal in minutes.
Useful references
- CDC carbon monoxide page: cdc.gov/co
- EPA indoor air quality CO page: epa.gov
- Consumer Product Safety Commission: cpsc.gov
Have not had your gas furnace checked this year? Heating tune-up with full combustion safety check from $99. 281-992-7866 or book online.