For the estimate method, the sub-calculator's operating time is set to \(t_{op}\) (hours per year) before calling estimate_method::calculate. The returned annual consumption (in kscf) is multiplied by 1000 to convert to standard cubic feet, then scaled by the units multiplier.

For the estimate method:

\begin{equation}\label{eq:leak-survey-estimate-annual} V_{annual} = C_{annual} \cdot 1000 \cdot n \end{equation}

     For the orifice method, and for the decibels method, the annual volume is
     computed from the instantaneous flow rate and the annual operating hours:

\begin{equation}\label{eq:leak-survey-time-based-annual} V_{annual} = t_{op} \cdot Q_{total} \cdot 60 \end{equation}

Symbols

\(V_{annual}\)	Annual compressed air volume lost through this survey entry \([\unit{ \scf}]\)
\(C_{annual}\)	Annual consumption from estimate_method::calculate \([\unit{ \kscf}]\)
\(1000\)	Kiloscf to standard cubic feet conversion \([\unit{ \unitless}]\)
\(n\)	Number of identical leak points (units multiplier) \([\unit{ \unitless}]\)
\(t_{op}\)	Annual compressed air system operating time \([\unit{ \hour\per\year}]\)
\(Q_{total}\)	Combined instantaneous flow rate for this entry \([\unit{ \scfm}]\)
\(60\)	Minutes per hour conversion \([\unit{ \minute\per\hour}]\)