SG 068/26
ANSI/CAN/UL 9540A:2026 signals a step-change in battery energy storage system (BESS) safety, putting independent, performance-driven fire validation at the center of compliant deployment.
As the global energy storage market scales, safety benchmarks are evolving from guidance-based frameworks toward mandatory, performance-driven validation. The sixth edition of ANSI/CAN/UL 9540A:2026 marks a significant shift in how BESS must demonstrate fire safety, directly impacting system design, testing strategies and certification timelines.
A major advancement is the introduction of a ‘passive-first’ safety philosophy for outdoor ground-mounted systems. This requires validation of thermal runaway containment without reliance on active systems such as heating, ventilation and air conditioning (HVAC) or suppression. Systems must maintain structural integrity and prevent propagation under loss-of-power conditions, a critical consideration for offshore and remote deployments. Additionally, revised test methods now require vertical initiation across full module groupings to better capture buoyancy-driven flame spread and heat flux escalation in rack configurations.
- Annex C (deflagration testing) becomes normative
Annex C transitions from informative to mandatory. If enclosure design and gas composition present an explosion risk, large-scale deflagration testing is required.
- Technical impact: deflagration is no longer a secondary consideration; it must be quantified through empirical test data
- Business impact: manufacturers must validate gas release behavior, venting strategies and pressure relief systems. Early-stage computational fluid dynamics (CFD) modeling becomes essential to avoid costly redesigns
- Passive-first requirement for outdoor systems
During installation level testing, active propagation-prevention systems must be disabled within the enclosure of origin.
- Technical impact: systems must rely on passive containment measures, including thermal barriers, fire-resistant materials and internal segmentation
- Strategic implication: designs dependent on active cooling alone may risk noncompliance, shifting R&D focus toward inherently safe architectures
- Enhanced vertical fire propagation testing
Testing now requires initiating thermal runaway across at least one full vertical module grouping.
- Technical impact: this captures the ‘chimney effect’ in vertical racks, where heat and flames accelerate upward propagation
- Business impact: increased test complexity, higher module requirements and expanded instrumentation requirements significantly raise upfront large-scale fire testing (LSFT) costs
- Expansion to high-temperature and long-duration energy storage (LDES) technologies
The standard now includes high-temperature battery container systems (e.g. sodium-sulfur).
- Technical impact: new methods address molten material containment and hazardous leakage
- Market impact: provides a defined compliance pathway for emerging Long-Duration Energy Storage (LDES) technologies, improving bankability and regulatory clarity
Preparing for transition
The sixth edition establishes a higher safety threshold across the industry. Systems certified under earlier editions should undergo gap analysis, particularly in passive containment and deflagration control.
Recommended Actions:
- Evaluate passive safety: confirm system performance without active cooling or suppression
- Validate venting design: reassess pressure relief and deflagration mitigation per Annex C
- Leverage simulation: use CFD and pre-compliance modeling to ensure first-pass LSFT success
Ultimately, this transition demands a more integrated engineering approach, where fire dynamics, system architecture and regulatory compliance are addressed in parallel. Early engagement between design teams and certification experts will be key to avoiding delays, controlling costs and ensuring safe, market-ready deployments.
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