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<\/figure>\n<\/div>\n\n\nUL Standards & Solutions recently published (13 March) the 6th<\/sup> edition of the key standard, or the \u2018Test method for evaluating thermal runaway fire propagation in BESS,\u2019 to give its full title.<\/p>\n\n\n\n UL9540A is widely recognised in the industry for assessing the safety of electrochemical energy storage systems (ESS), including, but not limited to, lithium-ion (Li-ion) BESS. It is considered the benchmark for evaluating safety, particularly in assessing thermal runaway and propagation risks and therefore critical to the bankability of energy storage technologies.<\/p>\n\n\n\n The new edition adds requirements for large-scale fire testing (LSFT)<\/a> alongside cell and module level tests, perhaps aimed at overcoming a perceived limitation in previous versions by adding focus on system-level safety. In large-scale fire testing, a single BESS unit is set on fire with all its fire suppression and detection systems disengaged and the results observed, typically with other BESS units placed nearby to assess propagation risk.<\/p>\n\n\n\n Commenting for Energy-Storage.news<\/em>, Dana Parmenter, commercial VP of industrial at testing and certification provider CSA Group, said that the release of the 6th<\/sup> edition \u201cestablishes a new precedent in the energy storage system (ESS) testing and certification ecosystem.\u201d<\/p>\n\n\n\n \u201cThis change will raise many questions for manufacturers around enforcement timelines, jurisdictional adoption, and how updated requirements may be interpreted by authorities having jurisdiction (AHJs),\u201d Parmenter said.<\/p>\n\n\n\n \u201cThis edition expands testing expectations and introduces LSFT requirements within the certification process. Section 10 requires LSFT to demonstrate that fire will not propagate between ESS units. This change is part of a larger trend across ESS standards, placing greater emphasis on LSFT as it relates to system-level safety.\u201d<\/p>\n\n\n\n Indeed, the growing emphasis on large-scale fire testing has been industry-wide. Many manufacturers and system integrators have been conducting LSFT on a voluntary basis as part of the adoption of best practices for the past year or so.<\/p>\n\n\n\n Since then, LSFT has become mandatory in the new 2026 edition<\/a> of the US National Fire Protection Association\u2019s BESS safety standard NFPA 855, as explained in a January 2026 Energy-Storage.news <\/em>article.<\/p>\n\n\n\nLarge-scale fire testing mandatory in NFPA 855 2026<\/h2>\n\n\n\n