The Hidden Variable: How Data Gaps Shape Battery Fire Safety Engineering

Abstract Lithium-ion battery systems are increasingly deployed across vehicles, buildings, and energy infrastructure, raising urgent fire safety challenges that are not yet fully addressed by existing codes and standards. This article presents findings from an international survey of fire safety professionals with experience in battery-related projects, designed to capture current practice, perceived gaps, and methodological limitations. The survey reveals strong reliance on heat release rate as a principal design parameter, yet limited recognition of the uncertainties associated with its measurement. Respondents emphasized the lack of validated, system-level test data, particularly on gas composition (primarily toxicity but also flammability), and concerns related to UL9540A goals, quality and interpretation. Concerns about transparency and unequal access to test data were repeatedly noted, alongside the absence of harmonized regulatory guidance across regions. Taken together, the results provide one of the first systematic insights into how fire safety engineers approach battery fire safety design/strategy in projects involving battery systems in practice and identify areas where research, regulation, and industry practice must converge to enable safe large-scale deployment of battery systems.