A refill is disclosed for an electronically activated dispenser of liquid volatiles, such as insecticides and fragrances. There is a bottle having a wick, a wick holder, a vent hole, an outlet, and a removable cap. When the cap is in place it covers both the wick and a vent hole. The cap seals the vent hole via an interference fit with a well adjacent the vent hole and also either a direct abutment against the vent hole or a surrounding of the vent hole. Also disclosed is a refill where the porous wick and vent hole are within defined size ranges so as to facilitate the use of a pyrethrum insecticide.