A special exception is a use that would not be appropriate generally or without restriction throughout a particular zone but which, if controlled as to number, area, duration, location or relation to the neighborhood, would promote the public health, safety, welfare, morals, order, comfort, convenience, appearance, prosperity or general welfare. Such uses may be permitted in a particular zone as an exception only if a specific provision for such exception is made in this chapter and then only by permission of the Board of Adjustment.