The formula provides a quick estimate of excess air based on measured flue gas oxygen content. For more complex fuel compositions, iterative refinement may be applied (as in solid_liquid_flue_gas_material::calculateExcessAirFromFlueGasO2).

\begin{equation}\label{eq:process-heat-excess-air} EA = \frac{k_1 \cdot O_{2,flue}}{2 - k_2 \cdot O_{2,flue}}\end{equation}

Symbols

\(EA\)	Excess air \([\unit{ \unitless}]\)
\(O_{2,flue}\)	Oxygen in flue gas \([\unit{ \unitless}]\)
\(k_1\)	Stoichiometric air factor (8.52381) \([\unit{ \unitless}]\)
\(k_2\)	Oxygen flue gas factor (9.52381) \([\unit{ \unitless}]\)

Implementation: See Excess Air from Flue Gas O2 for the complete formula, symbol definitions, and implementation details.