Lithium-ion batteries are now embedded in modern infrastructure — from electric mobility and energy storage systems (ESS) to data centers and industrial facilities. As these systems expand rapidly, incidents involving lithium-ion batteries are no longer rare or isolated events. They present a complex sequence of hazards including off-gas release, fire propagation, pressure buildup, and explosion. Despite this growing risk, practical operational frameworks for responders and safety professionals remain limited. Many existing resources focus on prevention or engineering design, while structured guidance for real-world incident response is still fragmented. This book presents a systematic operational framework for understanding and responding to lithium-ion battery incidents. Instead of treating battery fires as a single event, it analyzes incidents as a multi-stage process — from early off-gas generation to potential deflagration or explosion — and provides a structured decision framework for each stage. The manual focuses on practical field application . It introduces clear concepts and terminology that help responders interpret rapidly evolving situations, determine appropriate operational strategies, and avoid actions that may unintentionally escalate hazards. Key topics include: - Hazard development in lithium-ion battery incidents - Off-gas accumulation and ignition mechanisms - Explosion risk in confined battery environments - Strategic response frameworks for ESS and battery facilities - Operational decision points for emergency responders The framework presented in this manual is designed to be applicable across a wide range of environments including energy storage installations, electric mobility systems, industrial battery facilities , and other emerging lithium-ion battery infrastructures. As lithium-ion battery systems continue to expand worldwide, the ability to interpret incident progression and make structured operational decisions becomes increasingly critical. This manual aims to provide a clear conceptual foundation and practical guidance for those responsible for managing these incidents. Intended readers: firefighters, safety engineers, facility operators, and emergency planners who require a deeper understanding of lithium-ion battery hazards and response strategy.