The surge in demand for sustainable materials has instigated significant research into versatile substances applicable in fields ranging from everyday commodities to construction and energy. Among these, ionic liquids, notably 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][Tf2N]), have risen to prominence as green solvents. However, an urgent demand exists to comprehend their thermal safety characteristics, particularly for energy applications. Contrary to previous research, which predominantly employed linear fitting or empirical formulas, our study presents a novel non-linear fitting approach to investigate the thermal behavior of [EMIM][Tf2N]. It yields new insights into its activation energy value, marking a significant advance in attaining precise thermal safety data for sustainable construction applications. To ensure safety at elevated temperatures, [EMIM][Tf2N] was selected for comprehensive analysis. Our research evaluated the kinetic model using thermogravimetric analysis coupled with assessing fundamental reaction parameters and simulating thermodynamic equations by identifying hazardous temperatures. This study revealed that the reactivity hazard of [EMIM][Tf2N] escalated considerably when the temperature surpassed 280 °C, emphasizing the importance of process safety. Furthermore, when the temperature exceeded 287 °C, the time to reach the maximum reaction rate (TMR) diminished to less than a day—an aspect crucial to process safety. At temperatures beyond 300 °C, around 70% of the substance was consumed, further underlining the need for stringent safety measures in processing environments. We also considered the impact of different storage containers on thermal safety. The potential runaway temperatures for box-shaped and cylindrical storage containers were established at 270 °C and 280 °C, respectively, providing valuable data for designing safe storage environments. Our research significantly contributes to the prudent utilization and sustainable application of ionic liquids like [EMIM][Tf2N] by considering various safety scenarios and establishing safe temperature ranges.