An aerosol generating system comprises: a nicotine source (8) a volatile delivery enhancing compound source (10) wherein the volatile delivery enhancing compound comprises an acid and a heating means (18) for heating one or both of the nicotine source (8) and the volatile delivery enhancing compound source (10). One or both of the nicotine source (8) and the volatile delivery enhancing compound source (10) is encapsulated in a cylindrical polymeric capsule(2). The cylindrical polymeric capsule comprises a thermally conductive material.