Early in evaluating the destruction mechanisms of a number of organophosphorus compounds (OPCs), such as trimethyl phosphate (TMP), dimethyl methylphosphonate, and diisopropyl methylphosphonate, in connection with the disposal of chemical warfare agents, the promotion and inhibition effects of OPCs on stabilized flat flames of H-2 + O-2 were studied in detail. Because OPCs were demonstrated to be more effective fire suppressants than CF3Br (Halon 1301) and due to the need for replacing the currently used Halon 1301, further investigation of the effects of the OPCs on flames is of interest. Thus a lean flame of CH4/O-2/Ar (0.078/0.222/0.7) with and without TMP added, stabilized on a flat burner at 0.1 bar, was studied by molecular beam mass spectrometry (MBMS) and computer modeling using PREMIX and CHEMKIN codes. An experimental study of this flame revealed that TMP increases the width of the reaction zone by inhibiting the flame.