換気効率
T a i r ( x ) = c x ′ ( x ) c s {\displaystyle T_{\mathrm {air} }({\boldsymbol {x}})={\frac {c'_{x}({\boldsymbol {x}})}{c_{s}}}} c x ′ ( x ) {\displaystyle c'_{x}({\boldsymbol {x}})} :室内に総量q の汚染が一様発生したときの濃度分布、次の濃度に関する移流方程式の定常解: ∂ c x ′ ∂ t + ∂ c x ′ U j ∂ x j = q V {\displaystyle {\frac {\partial c'_{x}}{\partial t}}+{\frac {\partial c'_{x}U_{j}}{\partial x_{j}}}={\frac {q}{V}}}