Dallas Furnace Safety Checks Before Winter — Carbon Monoxide Risks

November in Dallas-Fort Worth is when the heating season truly begins. After several months of dormancy, gas furnaces in DFW homes fire up for their first extended runs of the year — and in some cases, reveal problems that developed over the summer. The most serious of these is a cracked or failed heat exchanger, which can allow combustion gases — including carbon monoxide — to mix with the air circulating through your home.

Understanding the Carbon Monoxide Risk

Carbon monoxide (CO) is produced by the combustion of natural gas in your furnace. Under normal operation, the combustion happens in the heat exchanger — a sealed metal chamber — and the CO-containing exhaust gases are vented outside through the flue pipe. Air from your living space never contacts the combustion gases.

When the heat exchanger cracks — which can happen due to age, thermal stress from years of expansion and contraction, or a history of restricted airflow from dirty filters — the barrier between combustion gases and living space air is compromised. The furnace fan then pushes CO-contaminated air through your duct system and into every room.

CO poisoning symptoms mimic the flu: headaches, nausea, dizziness, and fatigue. Because DFW homeowners often open windows during fall weather, the symptom onset is gradual and easy to misattribute. The danger is most acute during extended periods of cold when windows stay closed and the furnace runs continuously.

Signs of a Potential Heat Exchanger Problem

Several symptoms can indicate a cracked or failing heat exchanger:

• A soot or smoke smell when the furnace runs — combustion gases leaking into the air stream
• A yellow or flickering burner flame instead of a steady blue flame — indicates improper combustion
• Headaches or flu-like symptoms that improve when you leave the house
• CO detector alarming when the furnace runs
• Visible rust streaks on the outside of the heat exchanger (observable only during a professional inspection)

A heat exchanger inspection is not a DIY task. It requires disassembly of the furnace cabinet and in many cases specialized inspection tools. If you have a furnace that is more than 15 years old and has not been inspected recently, November is an important time to schedule that check.

Carbon Monoxide Detectors: Your Last Line of Defense

Every DFW home with a gas furnace should have functioning carbon monoxide detectors on every level and outside each sleeping area. CO detectors have a useful life of 5–7 years — after that, the electrochemical sensor degrades and may not detect CO reliably even if it appears to function.

Test your CO detectors now by pressing the test button. Replace batteries in any detector that is more than a year past its last battery change. If any detector is older than 7 years, replace the entire unit — the sensor, not just the battery.

If your CO detector alarms while the furnace is running: get everyone out of the house immediately, call 911, and do not re-enter until the fire department has cleared the home. Then call an HVAC technician before operating the furnace again.

Other November Furnace Safety Checks

Beyond the heat exchanger and CO detectors, check that the flue pipe on your furnace is intact, properly secured, and not rusted through at joints. The flue carries combustion gases from the heat exchanger to the outside — a disconnected or corroded flue joint can vent CO directly into the furnace room. Inspect visible sections of the flue for rust-through, disconnection at elbows, or bird nests blocking the termination cap.

Also check that the furnace area is clear of stored items, flammable materials, and debris. The minimum clearance requirement around a gas furnace varies by manufacturer but is typically 18 inches on all sides. Stored boxes, seasonal decorations, or lawn equipment in the furnace room are both a fire hazard and an airflow restriction.