An evaporation dispenser for freshening the air in closed spaces such as toilets, washrooms and waiting rooms, telephone booths and lifts. A mounting plate is arranged in a housing and is divided into two chambers by a horizontal separating surface. The lower chamber serves as an evaporation space and holds two bottles of active substance which form a saturated atmosphere in the chamber via evaporating elements. This atmosphere is diffused into the outside air by means of a fan which draws the saturated atmosphere from the evaporation space. Simultaneously, ambient air is drawn into the evaporation space to become saturated. Both the discharge of the saturated atmosphere and the drawing in of ambient air may be performed by a single rotor compressor, the rotor being divided into two sections by a radial divider. The discharge of the saturated atmosphere may be controlled by a microcontroller coupled to sensors which monitor activity in the closed space.