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Propane is an important practical fuel and its high temperature combustion is characterised by the rapid decomposition into smaller C 1 -C 3 intermediates [15.1]. This behaviour is similar to the combustion of more complex hydrocarbon fuels. From a modelling perspective, a propane combustion mechanism, compared to that of other higher hydrocarbons, requires the smallest number of species and reactions that are necessary for a thorough kinetic study of the CI-C3 species. Previous modelling studies of propane combustion with detailed [15.1,15.2] and simplified [15.3] chemistry have mainly focused on premixed flames with little attention given to non-premixed conditions [15.4-15.5]. There is also a lack of simplified mechanisms based on the systematic reduction of complex chemical mechanisms for non-premixed propane flames. The purpose of the present study is to formulate reduced reaction mechanisms based on the systematic theoretical investigation of propane-air diffusion flames using a planar counterflow geometry and the detailed chemistry defined in Chap. 1. Propane flames are here computed using rates of strain from lO/s to extinction at pressures ranging from 1 to 10 bar. The deduced mechanisms are also validated against the experimental results obtained by Tsuji and Yamaoka [15.6] for counterflow propane-air flames at strain rates of 150/s and 350/s. Using the results of the above computations the behaviour of non-premixed propane flames is analysed and the most important reaction paths indentified as functions of rate of strain and pressure. The validity of steady-state assumptions for intermediate species are also examined. Subsequent formulations of the reduced mechanisms are based on the use of steadystate assumptions for most of the species and the elimination of unimportant reactions from the original detailed mechanism.