A flue gas inspection is the process of analyzing the gases that are emitted through a heating system's flue or exhaust vent — typically from a furnace, boiler, water heater, or fireplace. It's used to check both efficiency and safety of combustion systems.

🔥 What Is “Flue Gas”?

Flue gas is the byproduct of burning fuel (natural gas, oil, propane, wood, etc.). It’s vented through a chimney or exhaust pipe and usually contains:

  • Carbon dioxide (CO₂)

  • Water vapor (H₂O)

  • Carbon monoxide (CO) — dangerous if not vented properly

  • Nitrogen oxides (NOₓ)

  • Oxygen (O₂)

  • Other trace gases

🛠️ What a Flue Gas Inspection Involves

  1. Combustion Analyzer Use
    A technician uses a handheld device to measure:

    • CO (carbon monoxide) levels

    • O₂ and CO₂ ratios

    • Flue gas temperature

    • Efficiency of the burner

    • Draft pressure (to make sure gases are flowing out properly)

  2. Visual Check of the Flue/Vent System

    • Look for blockages, corrosion, or leaks in vent pipes or chimneys.

    • Ensure proper slope and secure connections.

  3. Check for Proper Draft

    • A good draft ensures harmful gases are pulled out of the building.

    • Backdrafting or poor draft can lead to CO buildup inside.

✅ Why It’s Important

🔒 Safety

  • Detects carbon monoxide leaks — a serious health hazard.

  • Ensures flue gases are being vented safely and not backflowing into the living space.

🔧 Performance

  • Helps fine-tune fuel-burning equipment for optimal efficiency.

  • Can identify issues like incomplete combustion or incorrect air/fuel mixture.

🏠 Code Compliance

  • Some areas require it during annual maintenance, real estate transactions, or commercial inspections.

📍 Where You’d See It Used

  • Home inspections (especially with gas appliances)

  • Boiler/furnace tune-ups

  • Commercial HVAC inspections

  • Insurance or safety audits

🔍 Bonus: When to Get a Flue Gas Inspection

  • After installing or replacing a heating appliance

  • If you notice soot, smells, or yellow flames

  • As part of routine HVAC maintenance

  • If there's been a chimney or vent blockage