An apparatus for the dissemination of volatile liquid into an atmosphere comprises a reservoir containing the liquid, and a porous evaporative member that extends from the liquid into the atmosphere, the reservoir being directly open to the atmosphere only by a pressure equalisation vent, which vent is equipped with closing means that obstructs the vent to an increasing degree with increasing atmosphere temperature, optionally closing it completely. The apparatus thus reduces considerably the excessive loss of fragrance encountered in atmospheres that can get very hot, for example, automobile interiors.