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{8.52381 \cdot O_{2,flue}}{2 - 9.52381 \cdot O_{2,flue}}\end{equation}

Symbols

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

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