The 2026 edition of NFPA 855 shifts the center of gravity of ESS (Energy Storage System) safety standards from preventing ignition at the cell level to Thermal Runaway Propagation Prevention (TRPP) at the rack/container level. This revision is a line/system-engineering matter, not a problem of the battery's own material properties, in that it brings the entire BOS (Balance of System) — including cell-to-cell spacing, detection interfaces, and cooling wiring — into the scope of design. At the same time, mandatory pre-submission of the HMA (Hazard Mitigation Analysis) and ERP (Emergency Response Plan) to fire authorities has made a Traceability system that tracks and retains design-basis data at the rack level…