10/24/2026
🚨 A Routine Maintenance Call Uncovered a Serious Carbon Monoxide Hazard! 🚨
Today, our team at TCF Emergency Plumbing & Heating responded to a routine furnace and water heater maintenance appointment. The homeowner had found us through one of our Facebook advertisements.
During our visit, the homeowner mentioned that his grandson, who lives in the basement, had noticed a gas smell.
While inspecting the heating system, we discovered the furnace was overheating, and our professional gas detection equipment was registering 45 parts per million (PPM) of carbon monoxide near the water heater’s draft hood and base.
⚠️ What we discovered was extremely concerning.
The homeowners had recently had roofing work completed. During that process, the exhaust vent cap had been removed and reinstalled, leaving an obstruction at the top of the venting system.
Here’s where things became dangerous:
The furnace and water heater shared a venting system. Because the exhaust was obstructed at the roof, the furnace’s inducer motor was pushing combustion gases into the common vent, but those gases couldn’t properly escape outside.
Instead, the furnace exhaust was being forced backward through the water heater’s vent connector and spilling directly into the home through the water heater’s draft hood.
This meant that whenever the furnace operated, combustion gases containing carbon monoxide could enter the living space rather than safely exhausting outdoors.
We also observed the furnace overheating during operation.
🔍 Why is this so dangerous?
Many homeowners believe their carbon monoxide detector will immediately alert them whenever dangerous gases are present. Unfortunately, that’s not how standard residential CO alarms work.
Some residential alarms may take 1–4 hours to activate at approximately 70 PPM, and lower concentrations may not trigger an alarm.
We measured 45 PPM near the water heater, even without a household alarm necessarily sounding.
Prolonged carbon monoxide exposure can cause headaches, dizziness, nausea, fatigue, and more serious health complications. These gases can also migrate throughout the home.
Additionally, improper venting and backdrafting can contribute to condensation, corrosion, premature water heater deterioration, and even future water leaks or equipment failure.
✅ Fortunately, we identified the source and corrected the problem.
After removing the venting obstruction and restoring proper exhaust flow:
✅ The furnace exhaust was venting properly.
✅ The water heater was no longer experiencing backdrafting.
✅ The furnace overheating symptoms subsided.
✅ The equipment was operating properly during our follow-up testing.
One obstruction at the roof was affecting two separate heating appliances and creating a potentially dangerous situation inside the home.
🔬 This is why professional maintenance matters.
We use professional gas detection equipment to take live measurements of carbon monoxide, combustible gases, and volatile organic compounds (VOCs).
These instruments allow us to identify potential safety hazards that ordinary household alarms may not immediately detect.
We recommend inspecting and maintaining fuel-burning appliances at least once annually, with additional inspections whenever roofing work, venting modifications, or unusual operating conditions occur.
Carbon monoxide alarms are essential, but they are not a substitute for professional combustion and venting inspections.
What started as a routine maintenance appointment turned into identifying and correcting a potentially life-threatening hazard before it caused further damage.
At TCF Emergency Plumbing & Heating, we don’t just service equipment. We protect homes, investments, and most importantly, families.
🔧 TCF Emergency Plumbing & Heating
📍 Proudly serving Denver and surrounding Colorado communities.
