All flow resistances are dynamic pressure losses and change quadratically to the flow velocity v or to the volume flow q_V exceptions are laminar flows):
p_d=\frac{\rho}{2}\cdot v^2
Thus, the same laws apply as for fans, so that there is always an equilibrium when the fan and the system work together. To determine the required air performance, specifically p_{tot} of a fan system, all existing flow resistances (pressure losses) on the suction and pressure side of the fan must be added.
p_{tot}=\Sigma_{pK}+\Sigma_{pE}+p_{d,A}
p_K : Channel friction resistors
p_E : Individual resistances e.g. mold, baffle and apparatus resistances
p_{d,A} : Dynamic pressure in the discharge cross-section of the system
Note: Pressure losses across filters are usually not quadratic to flow velocity, due to non-turbulent flow.