Flammable and Toxic Gases from Batteries in Thermal Runaway: Consequences and mitigation

The widespread adoption of lithium-ion batteries (LIBs) across energy storage systems, electric vehicles, and consumer electronics is accelerating, yet the safety challenges associated with thermal runaway (TR) events remain incompletely understood. This report presents a structured review of current knowledge regarding flammable and toxic gas emissions from LIBs during TR, the consequences for fire behavior and explosion risk. Key application areas covered include battery energy storage systems (BESS), micro-mobility devices, emergency response practices, recycling processes, and emerging battery technologies. The report identifies and evaluates experimental and modeling studies on gas composition, explosion dynamics, fire suppression, and fire brigade interventions. While substantial data exist for flammable gas emissions, significant uncertainties remain around toxic gas species such as hydrogen fluoride (HF), as well as particulate matter and mixed combustion products. Explosion modeling shows promise, but is limited by inconsistencies in gas composition data and a lack of real-world validation. Fire suppression strategies and inerting agents, have been explored but show mixed or potentially counterproductive results under certain conditions. A comprehensive assessment of knowledge gaps reveals critical areas for future research: the need for realistic testing environments; better understanding of explosion risks in confined or complex geometries; validated, science-based firefighting tactics; and the urgent study of under-regulated segments such as micro-mobility devices and battery recycling operations. Additionally, emerging chemistries such as solid-state and sodium-ion batteries require proactive safety evaluations. Bridging these gaps is essential to improve safety standards, support regulatory frameworks, and guide societal adaptation to battery technologies.