Abstract: A diffuser for dispersing an aroma into a surrounding area includes a cartridge 100 having an aromatic substance dispersed in a wax carrier 102. The cartridge 100 includes a container 3 in which the wax carrier 102 is located and a cover 2 that includes a central vented tubular projection 27. The container is positioned in a heat conductive cup 6 and a heating element 7 is located below the cup 6 A fan 21 forces air past the cup 6 and aromatic vapors released when the wax carrier 102 is at least partially melted are entrained by the air currents and released through a vented dome 1 at the top of the diffuser. An outer cylindrical housing 12 is used to mount the components. When the heat is removed, the wax carrier solidifies, trapping the aromatic substance. The cartridge vent 27 extends into the container 3 and the annular volume around the inwardly projecting vent is sufficient to provide space for the melted wax if the diffuser is upset.