Dividing the mass flow rate (lbm/min) by the standard-condition density (lbm/ft³) gives the volumetric flow rate referenced to standard conditions (scfm). This conversion allows direct comparison of leak rates at different supply pressures and temperatures, since all values are normalized to the same reference state.

\begin{equation}\label{eq:orifice-method-volume-flow} Q_{scfm} = \frac{\dot{m}}{\rho_{std}} \end{equation}

Symbols

\(Q_{scfm}\)	Volumetric flow rate per orifice at standard conditions \([\unit{ \scfm}]\)
\(\dot{m}\)	Mass flow rate per orifice \([\unit{ \pound\per\minute}]\)
\(\rho_{std}\)	Air density at standard atmospheric conditions \([\unit{ \pound\per\cubicFoot}]\)