Hot wire ignition experiments were carried Out recently at the Canadian Explosives Research Laboratory oil a few emulsion formulations. The data indicate that there is a pressure-dependent onset temperature beyond which the wire temperature increases at in accelerated rate. In order to explain this observation and to detect this temperature more consistently. particularly at low pressures. the data are reanalysed by comparing the experimental wire temperature with that predicted from theory for the heating of an inert material. For this purpose. all analytical theory from the literature is reviewed and the numerical solution developed in this report is described, The latter call deal with more general Solutions With variable thermal properties and chemical reactions in the condensed medium surrounding the wire. A review of available data on the vapour pressure of ammonium nitrate (AN)/water solutions is carried out and one set of data is correlated analytically to allow the general prediction for any concentration of water. A model is proposed to predict the phase transition temperature based oil the energy balance of the endothermic effects of water vapourization and AN dissociation/decomposition and the heat input from the hot wire. The predicted onset temperatures are shown to be in reasonable to excellent agreement with experiment depending on the compositions, which include emulsions with 9%, 18% water and additional ingredients of sodium nitrate, sodium perchlorate and urea. It is postulated that the minimum burning pressure (MBP) would lie on the transition temperature/pressure curve. However. locating this point requires an accurate prediction of the heat feedback from the exothermic reaction zone in the gas phase.