18/5/2026
Stakeholders in the stationary battery sector are currently awaiting the publication of a new French ministerial order (“arrêté”) that will define the safety requirements applicable to installations classified for environmental protection (ICPE) under heading 2925-2, when they involve outdoor stationary lithium-based battery charging systems.
While this regulatory framework is still pending, many actors are turning to international standards that specify safety provisions for BESS. Among these, the latest edition of NFPA 855 confirms a major shift: fire and explosion safety for BESS is increasingly based on representative full-scale testing, and no longer only on cell- or module-level data.
This evolution strengthens the need for a multi-scale approach, capable of assessing hazards from the individual cell up to the complete system, taking into account the propagation of thermal runaway, gas generation and dispersion, overpressure and deflagration risks, and the interaction with the installation environment. NFPA has already indicated that the 2026 edition will include several important updates, notably making Hazard Mitigation Analysis (HMA) a standard component of safety evaluation for most BESS installations. This change significantly affects manufacturers, system designers, asset owners and authorities having jurisdiction (AHJs): project teams should now plan for an HMA early in the design and permitting process.
An HMA may include, for example, the assessment of initiation and propagation of thermal runaway, the evaluation of the generation and dispersion of hazardous gases, the analysis of deflagration and explosion potential, the evaluation of detection, suppression and ventilation systems, and the review of compartmentation strategies.
These analyses typically combine detailed design review, engineering modelling, fire test data (for example from UL 9540A and CSA C800), and performance-based safety assessments to demonstrate that the system can operate safely as designed. The updated standard also requires BESS installations to include explosion control and prevention measures designed in accordance with NFPA 69 or supported by installation-level fire and explosion testing and engineering evaluation. In contrast with previous editions, NFPA 68 deflagration venting is no longer accepted as a primary explosion control strategy, reflecting a move towards active prevention and control of hazardous gas accumulation.
Enhanced requirements are also introduced for Combustible Concentration Reduction (CCR) systems, which are intended to limit the build-up of hazardous gases during thermal runaway. These systems must remain operational under fault conditions and must consider gas composition and volume based on test data (such as UL 9540A), partial-volume deflagration scenarios, and the migration of hazardous gases between interconnected ESS units. All these developments further reinforce the central role of hazard evaluation, including HMA, in understanding the behaviour of hazardous gases and validating mitigation strategies.
Pending the development of testing and classification standards for the requirements of Article 12 and Annex V of the European battery regulation 2023/1542, Efectis can support manufacturers, system integrators and project developers across this entire evaluation chain. Under ISO/IEC 17025 accreditation, Efectis performs fire and explosion tests at all relevant scales – cell, module, unit and full system – for example in accordance with UL 9540A, to assess BESS fire and explosion behaviour.
Efectis experts also provide numerical studies to evaluate fire and explosion safety measures, such as assessing impact distances of thermal fluxes or supporting the design and sizing of explosion relief or mitigation systems. In the current context, these capabilities are crucial to securing BESS projects, demonstrating performance, and meeting the expectations of regulators and insurers.
For more information, please contact Mohamad el Houssami