Leaves or flat objects, waved to produce a more comfortable atmosphere, have not entirely given way to variable-speed mechanical devices. In the course of their development, fans have exhibited a great variety of materials, a richness of decorative artwork, and associations with sophisticated milieus that belie the origins of this humble and apparently universal tool.
Fans used in industry come in two main types, axial and centrifugal. Axial fans blow air across the axis of the fan, linearly, hence their name. Centrifugal fans blow air at right angles to the intake of the fan, and spin (centrifugally) the air outwards to the outlet.
wikipedia.org dumped 2003-03-17 with terodump