A reduced mechanism for propane/air combustion and its flame inhibition by phosphorus-containing compounds (PCCs) is constructed with the level of importance (LOI) method. The analysis is performed on solutions of freely propagating premixed flames with detailed chemical kinetics involving 121 species and 682 reactions proposed by Jayaweera

et al

. For the non-homogeneous reaction-diffusion system

the chemical lifetime of each species is weighted by its diffusion timescale

and the characteristic flame timescale is used to normalize the chemical lifetime. The definition of sensitivity in LOI is extended so that multi-parameters can be used as sensitivity targets. Propane

oxygen

dimethyl methylphosphonate (DMMP)

and flame speed are selected to be perturbed for sensitivity analysis

the species with low LOI index are removed

and reactions involving the redundant species are excluded from the mechanism. A skeletal mechanism is obtained

which consists of 57 species and 268 elementary reactions. Calculations for laminar flame speeds

key flame radicals and catalytic cycles using the skeletal mechanism are in good agreement with those by using the detailed mechanism over a wide range of equivalence ratio undoped and doped with DMMP.