A fire suppression system includes at least one high pressure gas source containing an inert gas, at least one low pressure gas source containing an organic halide gas, a distribution network connected with the high pressure gas source and the low pressure gas source to distribute the inert gas and the organic halide gas, and a controller in communication with the distribution network. The distribution network includes flow control devices configured to control flow of the inert gas and the organic halide gas. The controller is configured to initially release the inert gas in response to a fire threat to reduce an oxygen concentration at the fire threat below a preset oxygen concentration threshold, and release the organic halide gas to increase an organic halide gas concentration at the fire threat above a preset organic halide gas concentration threshold while the oxygen concentration is below the preset oxygen concentration threshold.