A combustion inspection analyzes gas furnace combustion efficiency by measuring oxygen and carbon dioxide levels in flue gas, verifying proper burner operation and fuel utilization. Testing typically includes draft verification, carbon monoxide levels below 400 ppm, and oxygen content between 2-6%. These measurements confirm complete combustion and safe furnace operation. Digital combustion analyzers provide rapid, accurate results compared to manual methods.
Technical Details
Technicians insert combustion analyzer probes into furnace flue pipes or draft diverters to sample combustion gases. Ideal natural gas combustion produces approximately 3-5% oxygen in the flue. Higher oxygen readings indicate excess air and reduced efficiency; lower readings suggest incomplete combustion and potential carbon monoxide production. Natural draft furnaces require negative draft of 0.02 to 0.05 inches water column; induced draft furnaces require specific positive pressure. Carbon monoxide should never exceed 400 ppm at the flue and 35 ppm in living spaces.
Practical Significance
Proper combustion ensures maximum heating efficiency and occupant safety. Poor combustion wastes fuel and increases carbon monoxide risk. Annual combustion inspection before heating season identifies burner problems, gas supply issues, or ventilation inadequacies. Combustion testing is essential for warranty compliance and code compliance in many jurisdictions.