An aerosol generating system comprises: a nicotine source (6) a volatile delivery enhancing compound source (10) downstream of the nicotine source wherein the volatile delivery enhancing compound comprises an acid heating means (18) for heating the nicotine source and a physically separate heat transfer barrier (8) between the nicotine source and the volatile delivery enhancing compound source. The heating means is preferably configured to heat the nicotine source to a temperature of between about 80°C and about 150°C. The heat transfer barrier is preferably configured so that in use the temperature of the volatile delivery enhancing compound source is less than about 50°C when the nicotine source is heated to a temperature of between 80°C and 150°C by the heating means. The heat transfer barrier may comprise a solid material having a thermal conductivity of less than about 1W per metre Kelvin (W/(m•K)) at 23°C and a relative humidity of 50%. Alternatively the heat transfer barrier may comprise a cavity having a length of at least about 8mm.
