Boiler Excess Air & Stack O2 Combustion Calculator

Determine percent excess air from dry stack oxygen (O2), stoichiometric air-fuel ratio, and quantify sensible stack heat losses via the Siegert equation.

Combustion Fuel & Flue Gas

Combustion Fuel Type:

Flue Gas Dry Oxygen O_2 (vol %): Measured by stack zirconia analyzer

Net Stack Flue Gas Temp T_flue (°F):

Combustion Air Intake Temp T_air (°F):

Boiler Firing Rate (MMBTU/hr):

Combustion & Efficiency Results

Percent Excess Air (% EA):

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Combustion Thermal Efficiency:

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Sensible Stack Heat Loss (q_stack):

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Flue Gas CO2 Concentration:

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Optimal Target O2 Range:

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Combustion Condition:

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Boiler Excess Air & Stack Loss Fundamentals

Stoichiometric combustion represents the exact theoretical air needed to burn fuel completely. Because industrial burners cannot achieve molecular mixing, a controlled excess of air ($10% - 25%$) is required to prevent incomplete combustion and dangerous carbon monoxide ($CO$) generation. However, every extra pound of excess air carries valuable sensible heat out the chimney stack.

Excess Air Calculation Formula

% Excess Air = [ O₂ / (20.9 - O₂) ] × 100%

Where $O_2$ is the percentage of dry oxygen measured by an in-situ zirconium oxide stack sensor.

Boiler Excess Air & Stack O2 Combustion Calculator

Combustion Fuel & Flue Gas

Combustion & Efficiency Results

Boiler Excess Air & Stack Loss Fundamentals

Excess Air Calculation Formula

Frequently Asked Questions