Source identification is critical for emergency responses to hazardous chemical releases, especially sudden releases of toxic gases. The timely arrangement of multiple sensors at the scene of a sudden accident is difficult. To overcome this limitation, a two-step source identification method based on a single sensor was developed. In the first step, the measured concentration was transmitted to the computing platform. First, a preliminary estimation of the release source was calculated from recently detected concentrations. Then, the preliminary result was used to predict the concentrations and to assess whether more measurements were needed. This data processing was conducted by the computing platform. In the second step, a new objective monitoring point was transmitted to the detector for the measurement of additional concentrations. These two steps were conducted repeatedly until the estimation adequately represented the release source. The fixed and mobile single sensor results were analyzed, and a comparison to multi-sensor results was also conducted. The results show that single-sensor source identification is attainable with a sufficient number of observations, and the number of valid concentration observations is required to be no less than the number of unknown parameters. To best estimate the release source, the movement strategy of the single sensor was based on the possible release source and the hazard partition of the gas plume. It is highly recommended that the single-sensor source identification method be used in unexpected incidents due to its flexibility and timely response. (C) 2019 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights reserved.