Abstract: A fan unit is designed for installation in ducting systems or in similar casings in air conditioning and ventilation systems. The fan unit has a freely turning radial impeller without any spiral housing and has a driving motor for the impeller. Downstream from the outlet of the impeller, there is a guiding structure for redirecting the flow coming radially out of the impeller to an axial direction.

Abstract: A radial fan has airfoil-like, backwardly curved blades placed between a support plate and a cover plate. The blades are so formed that the blade entry angle on the cover plate side is 4.degree. to 7.degree. smaller than the blade entry angle on the support plate side and the blade exit angle on the cover plate side is 3.degree. to 6.degree. smaller than the blade exit angle on the support plate side. The blade entry angle on the cover plate side is between 14.degree. and 20.degree. and the blade exit angle on the cover plate side is between 39.degree. and 45.degree.. This form is produced by twist of the blades or twist-free deformation thereof.