As battery energy storage systems (BESS) continue to increase in size and deployment, questions surrounding fire propagation and exposure protection have become increasingly important. Previous editions of NFPA 855 relied on UL 9540A testing to evaluate thermal runaway behavior and fire propagation potential. However, those test protocols did not require a sustained fire event involving ignition of vented gases, leaving uncertainty regarding how some systems could perform under more severe fire conditions.
To address this concern, the 2026 edition of NFPA 855 introduces new Large-Scale Fire Test (LSFT) requirements. The intent is to provide stakeholders with a more realistic understanding of fire propagation hazards and support risk-informed decisions regarding system spacing, exposure protection, and overall installation design.
What Changed in the 2026 Edition?
The new requirements mandate large-scale fire testing for electrochemical battery energy storage systems and include ignition of vented gases as part of the evaluation. The testing methodology is incorporated into the newly released sixth edition of UL 9540A and is intended to better represent credible fire scenarios that may occur in real-world installations.
The testing is designed to evaluate:
- Potential fire propagation between adjacent BESS units or groups
- Ignition hazards to nearby structures and combustible materials
- Appropriate separation distances between systems and exposures
- The effectiveness of proposed fire protection strategies in limiting fire spread
Rather than focusing solely on whether thermal runaway occurs, the new requirements place greater emphasis on understanding the consequences of a fire event and demonstrating that fire spread remains appropriately controlled.
Why This Matters for Project Teams
The implications of the new testing requirements extend well beyond manufacturers.
Owners and developers may need to revisit preliminary site layouts, spacing assumptions, and project constraints based on LSFT results. Designers and engineers must understand how tested configurations relate to proposed installations, particularly when reduced separation distances or higher energy capacities are being considered. AHJs will increasingly rely on testing documentation and engineering analyses to verify that proposed designs appropriately limit fire spread to adjacent equipment, structures, and exposures.
As jurisdictions begin adopting the 2026 edition of NFPA 855, project teams should expect additional scrutiny regarding how testing results are applied to specific projects. Early coordination between owners, developers, manufacturers, designers, and AHJs can help identify potential challenges before they affect permitting, schedule, or project execution.
This broader perspective reflects an important industry shift: In addition to meeting a prescriptive requirement, compliance also entails understanding risk, evaluating system performance, and demonstrating that proposed solutions support the life safety objectives of the code.
Looking Beyond Compliance
The introduction of large-scale fire testing represents an important step in the continued evolution of energy storage safety. By evaluating BESS installations under more representative fire conditions, stakeholders gain additional data to support informed decisions regarding system design, fire protection strategies, and exposure protection.
For project teams, the key takeaway is that LSFT results should not be viewed solely as a testing requirement. They should be viewed as a tool for understanding project-specific risk and validating that proposed installations can safely achieve their intended performance while protecting people, property, and adjacent operations. This risk-informed approach aligns with the fundamental intent of NFPA 855 and the ongoing effort to improve public safety as energy storage technologies continue to evolve.
How Code Red Consultants Can Help
Successfully navigating the new LSFT requirements requires more than understanding the test itself. It requires understanding how the results influence site planning, permitting, fire protection strategies, and project approvals.
Code Red Consultants works with owners, developers, manufacturers, designers, contractors, and AHJs to evaluate the fire protection and life safety implications of battery energy storage system installations. By combining expertise in code consulting, fire engineering, and regulatory coordination, we help project teams interpret testing results, assess project-specific risks, and develop solutions that support both compliance and public safety objectives. Our integrated perspective allows us to guide projects from planning and permitting through final approval, helping clients make confident decisions in an increasingly complex regulatory environment.