In my 8 years servicing DFW furnaces, I've condemned three heat exchangers for cracks, and every single time the homeowner had no idea. Carbon monoxide is colorless, odorless, and tasteless — the only way you know it's there is a working CO detector or a combustion analyzer in the hands of a licensed technician. As we head into heating season, this is the single most important safety conversation I have with homeowners across Farmers Branch, Coppell, Irving, Flower Mound, Lewisville, and Grapevine.
I'm Omar Jacobo, EPA 608 Universal Certified and co-owner of Frosty's HVAC LLC (TACLA126718E). If your family uses a gas furnace in DFW — which is most of you — read every word of this post before the first cold snap.
How Does a Furnace Produce Carbon Monoxide?
A gas furnace produces carbon monoxide as a normal byproduct of combustion, but a properly working furnace vents 100% of those gases outside through the flue. Carbon monoxide only becomes dangerous when something fails inside the combustion or venting path. Those failures fall into four categories:
- Cracked heat exchanger — the metal wall separating combustion gases from the air blowing through your ducts has a fissure, letting CO mix with the air going into your bedrooms
- Blocked or disconnected flue — nests, debris, or a joint that separated in the attic lets exhaust spill into the home instead of exiting the roof
- Incomplete combustion — a dirty burner, cracked ignitor, or improper gas/air mix creates more CO than the flue can handle
- Backdrafting — negative air pressure in the home pulls exhaust gases back down the flue (common in tight new construction with aggressive exhaust fans)
The Environmental Protection Agency reports that carbon monoxide kills over 400 Americans per year and sends 100,000+ to the ER. Most of those cases involve gas appliances — furnaces, water heaters, and generators.
Why Do We Never Repair a Cracked Heat Exchanger?
A cracked heat exchanger is always a full furnace replacement — no exceptions, no patches, no "we'll keep an eye on it." This is the most important safety rule at Frosty's HVAC, and I want to explain why I won't budge on it.
The heat exchanger is the metal barrier inside your furnace that separates the hot combustion gases (containing carbon monoxide, CO2, and water vapor) from the air that your blower pushes through the ductwork into every room. When that metal cracks — even a hairline you need a camera scope to see — combustion gases can leak into your breathing air every time the blower runs.
Heat exchangers crack from thermal stress. Every heating cycle, the metal expands and contracts. After 15-25 years of DFW winters, those cycles add up. A cracked exchanger will only get worse, never better. And the National Fire Protection Association explicitly warns against "repairing" cracks because welds and patches can fail under heat stress.
When I find a crack, here's what happens:
- I shut the furnace down immediately and tag it out of service
- I explain exactly what I found, with photos
- We build a full system replacement quote — $8,000 to $20,000+ depending on tier
- If the home is unsafe to occupy until replacement, I help arrange temporary heating
Any contractor who offers to "weld" or "patch" a cracked heat exchanger is putting your family at risk for a few thousand dollars in billable work. Walk away from that conversation.
Related: Gas Furnace Safety: What Every DFW Homeowner Must Know.
What Are the Warning Signs of a Furnace CO Problem?
The warning signs of a furnace carbon monoxide problem show up in both the equipment and the people in the home. Learn both lists — early detection saves lives.
Equipment warning signs:
- Yellow, orange, or flickering burner flame (should be a steady crisp blue)
- Soot streaks around the furnace cabinet or flue pipe
- Rust on the flue pipe or vent cap
- Excess moisture on interior windows near the furnace or registers
- A sharp chemical smell when the furnace runs (not gas — that's a separate emergency)
- Pilot light that keeps going out (on older furnaces)
- A CO detector that alarms even briefly
Human warning signs:
- Headaches that go away when you leave the house
- Dizziness, nausea, or confusion during heating season
- Flu-like symptoms without a fever
- Multiple family members (including pets) feeling unwell at the same time
- Unusual drowsiness or sluggishness when the furnace is running
If you or anyone in your home has flu-like symptoms that improve outside the house, treat it as a CO emergency. Get everyone outside, call 911, and then call (469) 254-0548 for emergency furnace inspection.
Where Should DFW Homeowners Install Carbon Monoxide Detectors?
Install a carbon monoxide detector on every floor of your home and within 10 feet of every sleeping area. Texas homes are slab-on-grade with no basements, which simplifies the layout — focus on the main living level, any second story, and outside bedroom doors.
Placement rules from the Consumer Product Safety Commission:
- One detector per floor, minimum
- Within 10 feet of every bedroom door
- At least 15 feet away from fuel-burning appliances (to prevent nuisance alarms)
- At least 10 feet away from bathrooms with a shower (humidity false alarms)
- 5 feet off the floor (CO is about the same weight as air and distributes evenly)
- Not in direct airflow from a supply register
What to buy: Any UL 2034 certified unit works. Combination smoke/CO detectors are fine and reduce the number of devices on the ceiling. Models with a 10-year sealed battery save you from forgetting battery changes. Plug-in units with battery backup work well in bedrooms.
What to avoid: Cheap unbranded detectors from overseas marketplaces. Stick with First Alert, Kidde, or Nest. These sensors save lives — don't bargain hunt.
Replace every 7-10 years. CO sensors degrade over time, even when the unit is working. Check the manufacture date on the back — not the battery replacement date.
What Does a Fall Furnace Safety Inspection Actually Include?
A real fall furnace safety inspection is a combustion analysis, not a visual glance and a sticker. When I perform a tune-up, here's exactly what happens:
| Safety Check | What It Measures | Why It Matters | |---|---|---| | Combustion analysis | CO, CO2, O2 in flue gas | Catches incomplete combustion before it harms you | | Heat exchanger inspection | Visible cracks, corrosion, soot | The #1 CO source | | Flue draw test | Pressure at the flue | Confirms exhaust is leaving the home | | Ambient CO reading | CO levels at the supply register | Verifies no CO is entering the breathing air | | Burner flame check | Color, steadiness, flame pattern | Yellow flames mean incomplete combustion | | Gas pressure test | Manifold pressure vs. manufacturer spec | Over/under pressure changes combustion | | Ignitor resistance | Ohm reading against spec | Weak ignitors cause delayed ignition and stress | | Safety switch test | High limit, flame rollout, pressure switch | Confirms safety shutoffs still work |
Fall tune-up pricing: $150 (Member: $127.50). Frosty Club Premium members ($300/yr) get two tune-ups per year included — spring AC and fall furnace.
This is not a 15-minute checklist visit. I spend 45-60 minutes on a proper furnace safety inspection because cutting corners on combustion testing is how people die.
Related: What Is a Heat Exchanger and Why Should You Care?.
What Should You Do If Your CO Detector Goes Off?
If your carbon monoxide detector sounds, get everyone outside immediately, then call 911, then call us. This is the exact sequence — in that order — because minutes matter.
- Get every person and pet out of the house. Leave the door open behind you for ventilation.
- Call 911 from outside. The fire department will come with calibrated CO meters to confirm and find the source.
- Do not re-enter until the fire department clears the home. Even if you feel fine.
- Call Frosty's at (469) 254-0548 after the fire department clears the scene. We will come out the same day to inspect the furnace, find the cause, and get you safely back into heating.
If the detector alarms briefly then stops — don't dismiss it. That's usually a real CO event that spiked high enough to alarm and then diluted. Schedule a professional inspection that week.
How Can DFW Families Stay Ahead of Furnace Safety?
The best defense against a furnace CO problem is catching it before it happens. I tell every homeowner the same three things going into heating season:
- Get a fall tune-up every single year. Combustion changes over time. Dust, rust, and thermal cycling shift the system. An annual tune-up ($150, Member: $127.50) catches problems when they're cheap fixes instead of emergencies.
- Replace furnaces that are 20+ years old. Even well-maintained furnaces develop heat exchanger stress after two decades. If yours is in that window, start budgeting. A full system replacement is $8,000 to $20,000+ — use our calculator for exact pricing.
- Test your CO detectors every month. Press the test button. If it doesn't scream, replace it. This takes 10 seconds per device and it's the last line of defense.
I've been in hundreds of DFW attics and closets inspecting furnaces since 2018. The homes I worry about are the ones where nobody has looked inside the furnace in 10 years. Don't be that home.
Schedule Your Fall Furnace Safety Inspection
Heating season is coming. I'd rather find a problem in September during a $150 tune-up than get a 3 a.m. emergency call in January. My team serves homeowners in Farmers Branch, Coppell, Irving, Flower Mound, Lewisville, and Grapevine — we're typically 15-25 minutes from every neighborhood in our service area.
Call (469) 254-0548 or request service online to book your fall safety inspection.
Considering a new system because yours is aging? Try our AC Replacement Cost Calculator for real pricing on all three tiers. Join Frosty Club to save on every service, and learn more about our team and credentials.
143 Google reviews, 4.9 stars, Texas License TACLA126718E, family-owned since 2018.
Related Articles
- Gas Furnace Safety: What Every DFW Homeowner Must Know
- What Is a Heat Exchanger and Why Should You Care?
- Pre-Season Furnace Checkup: Why September Is the Best Time
Written by Omar Jacobo, EPA 608 Universal Certified Lead Technician at Frosty's HVAC LLC. Family-owned since 2018, 143 Google reviews at 4.9 stars, Texas License TACLA126718E. Serving DFW homeowners with flat-rate pricing and no surprises.
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