fan static pressure at the originally specified duty pointpfs1fan static pressure at the specified volume after increase of the pressure losspfs2fan static pressure at the new duty point, along the fan static-pressure curve at original speedqV0fan volume flow rate, originally specifiedqV2fan volume flow rate at specified speed, after increase of pressure loss1fan characteristic curve, at the fan operating speed chosen according to the design operating point2fan static pressure curve at the increased speed, necessary to reinstate the specified volume flow rate3parabolic system resistance curve through the originally specified duty point4parabolic system resistance curve through the new duty points, due to system pressure-loss increaseFigure A.3 — Variations from design system curve