Carbon Monoxide and Your Heating System: What to Know

Carbon monoxide has no smell, no color, and no taste. That is the entire problem. A gas leak announces itself — the utility adds an odorant specifically so you notice. Carbon monoxide does not, and by the time somebody feels it, they are already being poisoned.

In North Texas we run our heat in short, hard bursts. A furnace sits idle most of the year, then a front drops in and it runs flat out for three days. That pattern hides problems, because a cracked heat exchanger or a blocked flue does not bother anyone in October. It bothers them the first cold night in January.

Where carbon monoxide actually comes from

Any appliance that burns fuel makes carbon monoxide. That is normal and expected. Complete combustion produces very little of it, and what is produced goes out the flue. The danger shows up when combustion goes incomplete, or when the exhaust does not leave the house the way it is supposed to.

In a typical home, the equipment worth thinking about is the gas furnace, the gas water heater, a gas range or oven, a fireplace, and anything attached to the house like a gas dryer. A furnace gets the most attention because it moves air through the whole home. If it produces CO, the blower distributes it to every room.

The failures we find most often

• A cracked heat exchanger — the metal wall separating combustion gases from the air you breathe develops a split from years of heating and cooling cycles.
• A blocked or disconnected flue — birds, wasp nests, debris, or a vent pipe that was bumped loose in the attic.
• A rusted or corroded vent connector, common on older water heaters sharing a flue with the furnace.
• A dirty or misaligned burner producing a lazy, sooty flame instead of clean combustion.
• A restricted return or a badly clogged filter starving the system of air.
• Backdrafting caused by an exhaust fan or a tight home pulling flue gases back down the vent.

That last one surprises people. A powerful range hood or an attic that has been air-sealed can put a house under enough negative pressure to reverse the draft on a natural-draft water heater. The appliance is fine. The house is fighting it.

Warning signs you can see and smell

You cannot detect CO with your senses, but you can often spot the conditions that produce it. These are worth a look before heating season:

• Burner flames that are yellow, orange, or flickering rather than crisp and blue.
• Soot, black streaking, or scorch marks around the furnace or water heater vent.
• Rust flakes or moisture on or under the vent pipe.
• Heavy condensation on windows near the furnace when it runs.
• A stale, stuffy, or slightly sharp smell when the heat kicks on.
• A vent pipe with visible gaps, a disconnected section, or a downward slope where it should rise.

The one you should never ignore is a health pattern. If two or more people in the house get headaches, nausea, or that heavy foggy feeling and it eases when they leave the home, that is a carbon monoxide pattern until proven otherwise. It gets written off as the flu constantly. Flu does not improve the moment you step into the driveway.

Detectors: where they go and how long they last

A CO alarm is inexpensive and it is the only thing standing between an invisible gas and your family. Put one on every level of the home and one outside each sleeping area. If your bedrooms are split across a hallway, you want coverage on both ends.

Carbon monoxide mixes with air rather than settling low, so mounting height is less critical than people assume. What matters more is not tucking it in a corner, right next to a bathroom, or within a few feet of the furnace or a gas appliance where normal startup can nuisance-trip it.

Two things homeowners routinely miss. First, the sensor inside a CO alarm wears out. Most units have a stamped end-of-life date and will chirp when they hit it. Replacing the battery does not reset a dead sensor. Second, smoke alarms are not CO alarms. Combination units exist and are clearly labeled. If yours does not say carbon monoxide on the housing, it does not detect it.

What to do when the alarm sounds

1. Get every person and pet outside into fresh air. Do this first, before anything else.
2. If anyone is dizzy, nauseated, confused, or unusually sleepy, call 911 from outside.
3. Do not go back in to open windows or to shut off the furnace. That trip is how people get hurt.
4. Once outside and safe, call us at (469) 338-5533 so a technician can find the source.
5. Do not run the heating system again until someone has tested it and cleared it.

If the alarm is chirping once every 30 to 60 seconds rather than sounding a continuous pattern, that is usually a low battery or end-of-life signal, not a detection. Check the unit's date stamp. When in doubt, treat it as real and step outside while you sort it out.

What a proper CO inspection looks like

When we come out on a CO call, we are not guessing. We check combustion at the appliance, verify draft at the flue, inspect the heat exchanger, look at the venting from the appliance all the way through the attic, and measure what the house is doing under pressure with exhaust fans running.

Be careful with anyone who quotes you a full furnace replacement on sight without testing combustion or inspecting the exchanger. A cracked heat exchanger is a genuine reason to shut a furnace down and replace it, and we will say so plainly when we find one. But it needs to be demonstrated, not assumed. You should be shown what was found.

Cost varies with what we find. A blocked flue or a loose vent connection is a modest repair. A dirty burner cleaned and re-tested is straightforward. A failed heat exchanger on an older furnace usually pushes toward replacement, and the spread there depends on system size, efficiency, and how much duct and venting work the install requires. We give you the numbers side by side before anything gets ordered.

Prevention, honestly

Most CO incidents we see trace back to something that a heating inspection would have caught. Have gas-burning equipment checked before heating season, keep filters changed so the system is not starved for air, keep the area around the furnace and water heater clear, and never run a generator, grill, or unvented heater in a garage or enclosed space. A cracked garage door is not ventilation.

Wilson Family Plumbing, Heating & Air is family-owned and based right here in Rockwall, and we work across Rockwall County and the Dallas metro. We hold a Texas Master Plumber license (TXM11693) and a Texas HVAC license (TACLB2360E), and we handle both the gas side and the equipment side, which matters on a CO call. If you smell something off, if your alarm has gone off, or if you just want the system checked before winter, call (469) 338-5533. Someone real answers, day or night.