Gas leaks represent a major concern in industrial sites due to potential human and economical losses. Prompt identification of leak scenarios favours corrective maintenance avoiding the domino effect. In this paper, long short-term memory recurrent neural networks were trained and tested to CH4 leakage source in a chemical process module. We exploit the benefits of varying the temporal length of input variables, and the datasets were obtained employing 3D-CFD simulations. We consider four leak locations, four wind speeds, and eight wind directions, besides the non-leakage scenario for the same wind speeds and directions. The models were trained using different values of timesteps to evaluate the prediction accuracy for unseen data. Results showed progressive improvement of the performance of the models with greater values of timesteps, and good generalisation with test accuracy over 95.3%, indicating the ability of the model to correctly predict the leakage source using easily monitored variables.