fan, device for agitating air or gases or moving them from one location to another. Mechanical fans with revolving blades are used for ventilation, in manufacturing, in winnowing grain, to remove dust, cuttings, or other waste, or to provide draft for a fire. They are also used to move air for cooling purposes, as in automotive engines and air-conditioning systems, and are driven by belts or by direct motor. The axial-flow fan (e.g., an electric table fan) has blades that force air to move parallel to the shaft about which the blades rotate. The centrifugal fan has a moving component, called an impeller, that consists of a central shaft about which a set of blades form a spiral pattern. When the impeller rotates, air that enters the fan near the shaft is moved away perpendicularly from the shaft and out of an opening in the scroll-shaped fan casing. As a light, flat instrument manipulated by hand to cool the body or ward off insects, the fan is of tropical origin and probably stems from the primitive use of palm or other leaves. The long-handled, disk-shaped fan carried by attendants was from ancient times associated with regal and religious ceremonies. In China an early form of the hand fan was a row of feathers mounted in the end of a handle; in Greece linen was often stretched over a leaf-shaped frame; and in Rome wooden fans, gilded and painted, were used. In Europe during the Middle Ages the fan virtually disappeared until the 13th and 14th cent., when fans from the Middle East were brought back by Crusaders and became fashionable for the wealthy. After 1500 the fan became generally popular; flag fans, disk-shaped fans, and tuft fans of ostrich plumes or peacock feathers, with handles of carved ivory or gold set with jewels, were common in women's wardrobes. In c.1600 the folding fan, developed in medieval Japan and introduced into Europe by way of China, became popular. The slats, of ivory, bone, mica, mother-of-pearl, or tortoiseshell, were delicately carved and covered with paper or fabric. The fan reached a high degree of artistry, especially in France, in the 17th and 18th cent. Delicately folded fans of lace, silk, or parchment were decorated with original designs and paintings by contemporary artists. The management of the fan became a highly regarded feminine art. The function and employment of the fan reached its high point of social significance in Japan.