8.4 Examples of the effects of poor inlet and outlet connectionsFigure 41 shows an example of a fan inlet and outlet where, due to duct sizes, there is a contraction on the fan inlet and expansion on the fan outlet. No account was taken of this when specifying the fan which led to a shortfall in air performance at the commissioning stage. Some modifications were made to the duct layout so that the fan performance was within the tolerance allowed by the contract.