A blower includes an electric motor case, a housing having a housing inlet and a housing outlet between which is defined a flow path for gas, a first impeller adapted to accelerate gas tangentially and to direct it radially outward, and a stationary portion. The stationary portion includes an annular gas flow path of sufficient width to allow a flow of gas therethrough without introducing excessive pressure drop. The stationary portion includes a first stator vane structure defining a plurality of stator vane leading edges, the first stator vane structure located on the second side of the motor and arranged to smoothly direct gas flow along a curved path. The motor case provides a shielding function for the stator vane leading edges from an impeller blade pressure pulse.