The emission of flammable and toxic gases during the thermal runaway of lithium-ion batteries (LIBs) poses a significant threat to the safety of energy storage stations (ESS). Consequently, gas detection technologies with rapid response, high sensitivity, and selectivity are crucial to enhance monitoring and early warning capabilities. Despite its importance, there has been limited development of gas detection methods specifically for energy storage stations. In this study, we have developed a novel gas monitoring method by integrating traditional gas sensors with Tunable diode laser absorption spectroscopy (TDLAS) to detect early generated gas before thermal runaway. In the experiment, a LiFePO4 (LFP) cell was heated with a heating rate of 60 W to stimulate a gradual thermal runaway. The battery surface temperature, ambient temperature, and pressure were measured to analyze thermal runaway phases and compare the response times of various detection methods. Notably, the methane (CH4) variation detected in TDLAS exhibited the fastest response with gas release five minutes earlier than other gases. CH4 release was detected in 413 s before the thermal runaway. The result demonstrated the superiority of the TDLAS gas detection system, particularly in terms of response time and non-destructive. The in-situ gas detection system can be applied to energy storage stations as it provides sufficient warning time by detecting early gas emissions.