The oil terminal is a facility for oil transportation and storage. Flammable gas detectors (FGDs) are able to reliably detect the release of hazardous liquid chemical materials in the tank area, but it cannot accurately obtain the key detecting parameters at the alarm time. This work analyzes the three stages of storage tank leakages under a static storage state. Firstly, the key elements affecting the leakage and detection are analyzed after considering the relative-position relationship of the horizontal distance from the jet point on ground level to the leak hole (X-jet), which denoted by the FGD's coordinate and the wind direction. Secondly, the denser-than-air dispersion is calculated by the SLAB model based on the liquid-pool radius determined by the bisection method (r), the liquid pool area corresponding to the alarm-response time can be ascertained, and then the detecting rapid response model (DRRM) for the leakage of the flammable liquid storage tank is established. Finally, the model was verified by a small-scale tank leakage and some crucial parameters such as X-jet, rand area of liquid pool, mass accumulating during the continuous leakage period (M) and total leaking time that corresponds to the time to alarm (T-total)are obtained. These findings provide scientific data for providing early warning and emergency response. (C) 2020 Published by Elsevier B.V. on behalf of Institution of Chemical Engineers.