BESS Thermal Runaway Emergency Response Protocol (PDF)

Thermal runaway in lithium-ion BESS is a self-sustaining exothermic cascade where localized cell overheating triggers adjacent cells to fail catastrophically—releasing flammable electrolytes, toxic gases (e.g., HF, CO), and intense heat (>800°C). The protocol addresses this hazard through layered defense: early detection via multi-sensor monitoring (temperature, voltage, gas, smoke), rapid physical and electrical isolation (contactors, DC breakers, module-level fusing), and targeted suppression (e.g., aqueous film-forming foam (AFFF), inert gas flooding, or water mist with thermal mass considerations). It emphasizes time-critical decision trees—differentiating between incipient, active, and post-event phases—and mandates predefined communication channels, evacuation zones, and PPE requirements aligned with NFPA 855, UL 9540A, and IEC 62933-5-2 standards. Crucially, the protocol integrates system-specific data (cell chemistry, pack architecture, ventilation design) to tailor response thresholds and suppression strategies, recognizing that generic approaches may exacerbate hazards—for example, excessive water application on high-energy-density NMC packs can induce steam explosions or electrical shorting. Finally, it includes post-incident protocols for hazardous material handling, forensic data logging (BMS event logs, CCTV, sensor timestamps), and mandatory root-cause analysis to inform design updates and procedural refinement.